mirror of
https://github.com/fluencelabs/aqua-book
synced 2024-12-04 15:20:19 +00:00
GitBook: [alpha] 23 pages and one asset modified
This commit is contained in:
boneyard93501
gitbook-bot
parent
d26e4e086c
commit
f236d822d8
BIN
.gitbook/assets/screen-shot-2021-06-29-at-1.06.39-pm.png
Normal file
BIN
.gitbook/assets/screen-shot-2021-06-29-at-1.06.39-pm.png
Normal file
Binary file not shown.
|
After Width: | Height: | Size: 982 KiB |
@ -1,5 +1,30 @@
|
||||
# Installation
|
||||
|
||||
* native tools
|
||||
* devcontianer ?
|
||||
Both the Aqua compiler and support library can be installed natively with `npm`
|
||||
|
||||
To install the compiler:
|
||||
|
||||
```bash
|
||||
npm -g install @fluencelabs/aqua-cli
|
||||
```
|
||||
|
||||
and to make the Aqua library available to Typescript applications:
|
||||
|
||||
```bash
|
||||
npm -g install @fluencelabs/aqua-lib
|
||||
```
|
||||
|
||||
Moreover, a VSCode syntax-highlighting extension is available. In VSCode, click on the Extensions button, search for `aqua`and install the extension.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
@ -1,10 +1,10 @@
|
||||
# Quick Start
|
||||
|
||||
Every Fluence reference node comes with a set of builtin services which are accessible to Aqua programs. Let's use those readily available services to get the timestamp of a few of our peer-to-peer neighborhood nodes with Aqua.
|
||||
Every Fluence reference node comes with a set of builtin services that are accessible to Aqua programs. Let's use those readily available services to get the timestamp of a few of our peer-to-peer neighbourhood nodes with Aqua.
|
||||
|
||||
{% tabs %}
|
||||
{% tab title="Timestamps With Aqua" %}
|
||||
```text
|
||||
```haskell
|
||||
-- timestamp_getter.aqua
|
||||
-- bring the builtin services into scope
|
||||
import "builtin.aqua"
|
||||
@ -40,13 +40,13 @@ func ts_getter(node: string) -> []u64:
|
||||
{% endtab %}
|
||||
|
||||
{% tab title="Compiling Aqua Script" %}
|
||||
```
|
||||
```bash
|
||||
aqua-cli -i aqua-scripts -o air-scripts -a
|
||||
```
|
||||
{% endtab %}
|
||||
|
||||
{% tab title="Result" %}
|
||||
```
|
||||
```bash
|
||||
fldist run_air -p air-scripts/timestamp_getter.ts_getter.air -d '{"node":"12D3KooWHLxVhUQyAuZe6AHMB29P7wkvTNMn7eDMcsqimJYLKREf"}' --generated
|
||||
[
|
||||
[
|
||||
@ -66,30 +66,30 @@ fldist run_air -p air-scripts/timestamp_getter.ts_getter.air -d '{"node":"12D3K
|
||||
{% endtab %}
|
||||
{% endtabs %}
|
||||
|
||||
The Aqua script essentially creates a workflow originating from our client peer to enumerate our neighbor peers from the Kademlia neighborhood based on our reference node specification, calls on the builtin timestamp service on each peer in parallel, joins the results stream after we collect ten timestamps and return our u64 array of timestamps back to the client peer.
|
||||
The Aqua script essentially creates a workflow originating from our client peer to enumerate our neighbour peers from the Kademlia neighbourhood based on our reference node specification, calls on the builtin timestamp service on each peer in parallel, joins the results stream after we collect ten timestamps and return our u64 array of timestamps back to the client peer.
|
||||
|
||||
See the [ts-oracle example](https://github.com/fluencelabs/examples/tree/main/ts-oracle) for the corresponding Aqua files in the `aqua-script` directory. Now that we have our script, let's compile it with the aqua-cli tool and find our AIR file in the air-scripts directory:
|
||||
See the [ts-oracle example](https://github.com/fluencelabs/examples/tree/main/ts-oracle) for the corresponding Aqua files in the `aqua-script` directory. Now that we have our script, let's compile it with the `aqua-cli` tool and find our AIR file in the `air-scripts` directory:
|
||||
|
||||
{% tabs %}
|
||||
{% tab title="Compile" %}
|
||||
```text
|
||||
```bash
|
||||
aqua-cli -i aqua-scripts -o air-scripts -a
|
||||
```
|
||||
{% endtab %}
|
||||
|
||||
{% tab title="Result" %}
|
||||
```
|
||||
```bash
|
||||
# in the air-script dir you should have the following file
|
||||
timestamp_getter.ts_getter.air
|
||||
```
|
||||
{% endtab %}
|
||||
{% endtabs %}
|
||||
|
||||
Once we have our AIR file we can either use a Typescript or command line client. Let's use the command line client `flidst`:
|
||||
Once we have our AIR file we can either use a Typescript or command-line client. Let's use the command line client `flidst`:
|
||||
|
||||
{% tabs %}
|
||||
{% tab title="Run Air scripts" %}
|
||||
```text
|
||||
```bash
|
||||
# if you don't have fldist on your machine:
|
||||
# npm -g install @fluencelabs/fldist
|
||||
# execute the AIR script from our compile phase with a peer id
|
||||
@ -98,7 +98,7 @@ fldist run_air -p air-scripts/timestamp_getter.ts_getter.air -d '{"node":"12D3K
|
||||
{% endtab %}
|
||||
|
||||
{% tab title="Output" %}
|
||||
```
|
||||
```bash
|
||||
# here we go: ten timestamps in micro seconds obtained in parallel
|
||||
[
|
||||
[
|
||||
@ -118,5 +118,5 @@ fldist run_air -p air-scripts/timestamp_getter.ts_getter.air -d '{"node":"12D3K
|
||||
{% endtab %}
|
||||
{% endtabs %}
|
||||
|
||||
And that's it. We now have ten timestamps right from our Kademlia neighbors.
|
||||
And that's it. We now have ten timestamps right from our Kademlia neighbours.
|
||||
|
||||
|
||||
@ -1,6 +1,6 @@
|
||||
# Abilities & Services
|
||||
|
||||
While Execution flow organizes the flow from peer to peer, Abilities & Services describe what exactly can be called on these peers, and how to call it.
|
||||
While [Execution flow](flow/) organizes the flow from peer to peer, Abilities & Services describe what exactly can be called on these peers, and how to call it.
|
||||
|
||||
Ability is a concept of "what is possible in this context": like a peer-specific trait or a typeclass. It will be better explained once abilities passing is implemented.
|
||||
|
||||
@ -8,9 +8,9 @@ Ability is a concept of "what is possible in this context": like a peer-specific
|
||||
|
||||
### Services
|
||||
|
||||
A Service interfaces functions \(often WASM ones\) executable on a peer. Example of service definition:
|
||||
A Service interfaces functions \(often provided via WebAssembly interface\) executable on a peer. Example of service definition:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
service MyService:
|
||||
foo(arg: string) -> string
|
||||
bar() -> bool
|
||||
@ -23,7 +23,7 @@ Service functions in Aqua have no function body. Computations, of any complexity
|
||||
|
||||
Some services may be singletons available on all peers. Such services are called built-ins, and are always available in any scope.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Built-in service has a constant ID, so it's always resolved
|
||||
service Op("op"):
|
||||
noop()
|
||||
@ -37,7 +37,7 @@ func foo():
|
||||
|
||||
A peer may host many services of the same type. To distinguish services from each other, Aqua requires Service resolution to be done: that means, the developer must provide an ID of the service to be used on the peer.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
service MyService:
|
||||
noop()
|
||||
|
||||
|
||||
@ -2,24 +2,24 @@
|
||||
|
||||
Aqua is an opinionated domain-specific language. It's structured with significant indentation.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Comments begin with double-dash and end with the line (inline)
|
||||
func foo(): -- Comments are allowed almost everywhere
|
||||
-- Body of the block expression is indented
|
||||
bar(5)
|
||||
```
|
||||
|
||||
Values in Aqua have types, which are designated by a colon, `:`, as seen in function signature below. The type of a return, which is yielded when a function is executed, is denoted by an arrow pointing to the right `->` , whereas yielding is denoted by an arrow pointing to the left `<-`.
|
||||
Values in Aqua have types, which are designated by a colon, `:`, as seen in the function signature below. The type of a return, which is yielded when a function is executed, is denoted by an arrow pointing to the right `->` , whereas yielding is denoted by an arrow pointing to the left `<-`.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Define a function that yields a string
|
||||
func bar(arg: i16) -> string:
|
||||
-- Call a function
|
||||
smth(arg)
|
||||
|
||||
|
||||
-- Yield a value from a function
|
||||
x <- smth(arg)
|
||||
|
||||
|
||||
-- Return a yielded results from a function
|
||||
<- "return literal"
|
||||
```
|
||||
@ -52,5 +52,3 @@ Reference:
|
||||
|
||||
* [Expressions](expressions/)
|
||||
|
||||
|
||||
|
||||
|
||||
@ -1,22 +1,22 @@
|
||||
# CRDT Streams
|
||||
|
||||
In Aqua, ordinary value is a name that points to a single result:
|
||||
In Aqua, an ordinary value is a name that points to a single result:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
value <- foo()
|
||||
```
|
||||
|
||||
Stream is a name that points to a number of results \(zero or more\):
|
||||
A stream , on the other hand, is a name that points to zero or more results:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
value: *string
|
||||
value <- foo()
|
||||
value <- foo()
|
||||
```
|
||||
|
||||
Stream is a kind of [collection](types.md#collection-types), and can be used where other collections are:
|
||||
Stream is a kind of [collection](types.md#collection-types) and can be used in place of other collections:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo(peer: string, relay: ?string):
|
||||
on peer via relay:
|
||||
Op.noop()
|
||||
@ -34,23 +34,23 @@ func bar(peer: string, relay: string):
|
||||
foo(peer, relayMaybe)
|
||||
```
|
||||
|
||||
But the most powerful uses of streams come along with parallelism, which incurs non-determinism.
|
||||
But the most powerful use of streams pertains to their use with parallel execution, which incurs non-determinism.
|
||||
|
||||
### Streams lifecycle and guarantees
|
||||
### Streams: Lifecycle And Guarantees
|
||||
|
||||
Streams lifecycle can be divided into three stages:
|
||||
A stream's lifecycle can be separated into three stages:
|
||||
|
||||
* Source: \(Parallel\) Writes to a stream
|
||||
* Map: Handling the stream values
|
||||
* Sink: Converting the resulting stream into scalar
|
||||
* Sink: Converting the resulting stream into a scalar
|
||||
|
||||
Consider the following example:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo(peers: []string) -> string:
|
||||
resp: *string
|
||||
|
||||
-- Will go to all peers in parallel
|
||||
-- Go to all peers in parallel
|
||||
for p <- peers par:
|
||||
on p:
|
||||
-- Do something
|
||||
@ -71,15 +71,15 @@ func foo(peers: []string) -> string:
|
||||
|
||||
```
|
||||
|
||||
In this case, for each peer in peers, something is going to be written into resp stream.
|
||||
In this case, for each peer in peers, something is going to be written into `resp` stream.
|
||||
|
||||
Every peer p in peers does not know anything about how the other iterations proceed.
|
||||
Every peer `p` in peers does not know anything about how the other iterations proceed.
|
||||
|
||||
Once something is written to resp stream, the second for is triggered. It's the mapping stage.
|
||||
Once something is written to `resp` stream, the second for is triggered. This is the mapping stage.
|
||||
|
||||
And then the results are sent to the first peer, to call Op.identity there. This Op.identity waits until element number 5 is defined on resp2 stream.
|
||||
And then the results are sent to the first peer, to call Op.identity there. This Op.identity waits until element number 5 is defined on `resp2` stream.
|
||||
|
||||
When it is, stream as a whole is consumed to produce a scalar value, which is returned.
|
||||
When the join is complete, the stream is consumed by the concatenation service to produce a scalar value, which is returned.
|
||||
|
||||
During execution, involved peers have different views on the state of execution: parallel branches of for have no access to each other's data. Finally, execution flows to the initial peer. Initial peer merges writes to the resp stream, and merges writes to the resp2 stream. It's done in conflict-free fashion. More than that, head of resp, resp2 streams will not change from each peer's point of view: it's immutable, and new values are only appended. However, different peers may have different order of the stream values, depending on the order of receiving these values.
|
||||
During execution, involved peers have different views on the state of execution: each of the `for` parallel branches have no view or access to the other branches' data and eventually, the execution flows to the initial peer. The initial peer then merges writes to the `resp` stream and to the `resp2` stream, respectively. These writes are done in conflict-free fashion. Furthermore, the respective heads of the `resp`, `resp2` streams will not change from each peer's point of view as they are immutable and new values can only be appended. However, different peers may have a different order of the stream values depending on the order of receiving these values.
|
||||
|
||||
|
||||
@ -10,15 +10,21 @@ Essentially, a function is an arrow. The function call is an expression that con
|
||||
|
||||
Finally, all a function does is call its arguments or service functions.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
service MySrv:
|
||||
foo()
|
||||
|
||||
func do_something(): -- arrow of type: -> ()
|
||||
MySrv "srv id"
|
||||
MySrv.foo()
|
||||
MySrv.foo()
|
||||
```
|
||||
|
||||
{% hint style="warning" %}
|
||||
TODO
|
||||
|
||||
* list all expressions
|
||||
* for each, explain the contract and provide a use case
|
||||
{% endhint %}
|
||||
|
||||
|
||||
|
||||
|
||||
@ -1,16 +1,16 @@
|
||||
# Header
|
||||
|
||||
### Header expressions
|
||||
## Header expressions
|
||||
|
||||
`import`
|
||||
### `import`
|
||||
|
||||
The `import` expression brings everything defined within the imported file into the scope.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
import "path/to/file.aqua"
|
||||
```
|
||||
|
||||
The to be imported file path is first resolved relative to the source file path followed by checking for an `-imports` directories.
|
||||
The to be imported file path is first resolved relative to the source file path followed by checking for an `-imports` directories.
|
||||
|
||||
See [Imports & Exports](../statements-1.md) for details.
|
||||
|
||||
|
||||
@ -4,15 +4,13 @@ description: Static configuration pieces that affect compilation
|
||||
|
||||
# Overrideable constants
|
||||
|
||||
|
||||
|
||||
`const`
|
||||
### `const`
|
||||
|
||||
Constant definition.
|
||||
|
||||
Constants can be used all across functions, exported and imported. If a constant is defined using `?=` , it can be overriden by value via compiler flags or imported values.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- This can be overriten with -const "target_peer_id = \"other peer id\""
|
||||
const target_peer_id ?= "this is a target peer id"
|
||||
|
||||
|
||||
@ -1,6 +1,6 @@
|
||||
# Services
|
||||
|
||||
`service`
|
||||
### `service`
|
||||
|
||||
Service definition.
|
||||
|
||||
@ -10,11 +10,11 @@ In the service definition, you enumerate all the functions, their names, argumen
|
||||
|
||||
Services that are a part of the protocol, i.e. are available from the peer node, come along with IDs. Example of predefined service:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
service Peer("peer"):
|
||||
foo() -- no arguments, no return
|
||||
bar(i: bool) -> bool
|
||||
|
||||
|
||||
func usePeer() -> bool:
|
||||
Peer.foo() -- results in a call of service "peer", function "foo", on current peer ID
|
||||
z <- Peer.bar(true)
|
||||
@ -23,11 +23,11 @@ func usePeer() -> bool:
|
||||
|
||||
Example of a custom service:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
service MyService:
|
||||
foo()
|
||||
bar(i: bool, z: i32) -> string
|
||||
|
||||
|
||||
func useMyService(k: i32) -> string:
|
||||
-- Need to tell the compiler what does "my service" mean in this scope
|
||||
MyService "my service id"
|
||||
@ -36,7 +36,7 @@ func useMyService(k: i32) -> string:
|
||||
-- Need to redefine MyService in scope of this peer as well
|
||||
MyService "another service id"
|
||||
z <- MyService.bar(false, k)
|
||||
<- z
|
||||
<- z
|
||||
```
|
||||
|
||||
Service definitions have types. Type of a service is a product type of arrows. See [Types](../types.md#type-of-a-service-and-a-file).
|
||||
|
||||
@ -1,23 +1,23 @@
|
||||
# Type definitions
|
||||
|
||||
`data`
|
||||
### `data`
|
||||
|
||||
[Product type](../types.md#products) definition. See [Types](../types.md) for details.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
data SomeType:
|
||||
fieldName: FieldType
|
||||
otherName: OtherType
|
||||
third: []u32
|
||||
```
|
||||
|
||||
`alias`
|
||||
### `alias`
|
||||
|
||||
Aliasing a type to a name.
|
||||
|
||||
It may help with self-documented code and refactoring.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
alias PeerId: string
|
||||
alias MyDomain: DomainType
|
||||
```
|
||||
|
||||
@ -4,13 +4,10 @@ Aqua supports branching: you can return one value or another, recover from the e
|
||||
|
||||
### Contract
|
||||
|
||||
The second arm of the conditional operator is executed iff the first arm failed.
|
||||
|
||||
The second arm has no access to the first arm's data.
|
||||
|
||||
A conditional block is considered executed iff any arm was executed successfully.
|
||||
|
||||
A conditional block is considered failed iff the second \(recovery\) arm fails to execute.
|
||||
* The second arm of the conditional operator is executed if and only if the first arm failed.
|
||||
* The second arm has no access to the first arm's data.
|
||||
* A conditional block is considered "executed" if and only if any arm was executed successfully.
|
||||
* A conditional block is considered "failed" if and only if the second \(recovery\) arm fails to execute.
|
||||
|
||||
### Conditional operations
|
||||
|
||||
@ -18,7 +15,7 @@ A conditional block is considered failed iff the second \(recovery\) arm fails t
|
||||
|
||||
Tries to perform operations, or swallows the error \(if there's no catch, otherwise after the try block\).
|
||||
|
||||
```text
|
||||
```haskell
|
||||
try:
|
||||
-- If foo fails with an error, execution will continue
|
||||
-- You should write your logic in a non-blocking fashion:
|
||||
@ -31,7 +28,7 @@ try:
|
||||
|
||||
Catches the standard error from `try` block.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
try:
|
||||
foo()
|
||||
catch e:
|
||||
@ -40,7 +37,7 @@ catch e:
|
||||
|
||||
Type of `e` is:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
data LastError:
|
||||
instruction: string -- What AIR instruction failed
|
||||
msg: string -- Human-readable error message
|
||||
@ -51,7 +48,7 @@ data LastError:
|
||||
|
||||
If corresponds to `match`, `mismatch` extension of π-calculus.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
x = true
|
||||
if x:
|
||||
-- always executed
|
||||
@ -74,7 +71,7 @@ Both operands can be variables.
|
||||
|
||||
Just the second branch of `if`, in case the condition does not hold.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
if true:
|
||||
foo()
|
||||
else:
|
||||
@ -87,7 +84,7 @@ If you want to set a variable based on condition, see Conditional return.
|
||||
|
||||
You may add `otherwise` to provide recovery for any block or expression:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
x <- foo()
|
||||
otherwise:
|
||||
-- if foo can't be executed, then do bar()
|
||||
@ -98,7 +95,7 @@ otherwise:
|
||||
|
||||
In Aqua, functions may have only one return expression, which is very last. And conditional expressions cannot define the same variable:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
try:
|
||||
x <- foo()
|
||||
otherwise:
|
||||
@ -107,7 +104,7 @@ otherwise:
|
||||
|
||||
So to get the value based on condition, we need to use a [writeable collection](../types.md#collection-types).
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- result may have 0 or more values of type string, and is writeable
|
||||
resultBox: *string
|
||||
try:
|
||||
|
||||
@ -1,14 +1,14 @@
|
||||
# Iterative
|
||||
|
||||
π-calculus has a notion of repetitive process: `!P = P | !P`. That means, you can always fork a new `P` process if you need it.
|
||||
π-calculus has a notion of the repetitive process: `!P = P | !P`. That means, you can always fork a new `P` process if you need it.
|
||||
|
||||
In Aqua, two operations corresponds to it: you can call a service function \(it's just available when it's needed\), and you can use `for` loop to iterate on collections.
|
||||
In Aqua, two operations correspond to it: you can call a service function \(it's just available when it's needed\), and you can use `for` loop to iterate on collections.
|
||||
|
||||
### For expression
|
||||
### `for` expression
|
||||
|
||||
In short, `for` looks like the following:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
xs: []string
|
||||
|
||||
for x <- xs:
|
||||
@ -21,19 +21,16 @@ y <- baz()
|
||||
|
||||
### Contract
|
||||
|
||||
Iterations of `for` loop are executed sequentially by default.
|
||||
* Iterations of `for` loop are executed sequentially by default.
|
||||
* Variables defined inside `for` loop are not available outside.
|
||||
* `for` loop's code has access to all variables above.
|
||||
* `for` can be executed on a variable of any [Collection type](../types.md#collection-types).
|
||||
|
||||
Variables defined inside for loop are not available outside.
|
||||
|
||||
For loop's code has access to all variables above.
|
||||
|
||||
For can be executed on a variable of any [Collection type](../types.md#collection-types).
|
||||
|
||||
### Conditional for
|
||||
### Conditional `for`
|
||||
|
||||
You can make several trials in a loop, and break once any trial succeeded.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
xs: []string
|
||||
|
||||
for x <- xs try:
|
||||
@ -41,9 +38,9 @@ for x <- xs try:
|
||||
foo(x)
|
||||
```
|
||||
|
||||
Contract is changed as in [Parallel](parallel.md#contract) flow.
|
||||
The contract is changed as in [Parallel](parallel.md#contract) flow.
|
||||
|
||||
### Parallel for
|
||||
### Parallel `for`
|
||||
|
||||
Running many operations in parallel is the most commonly used pattern for `for`.
|
||||
|
||||
@ -60,13 +57,13 @@ for x <- xs par:
|
||||
par continueWithBaz()
|
||||
```
|
||||
|
||||
Contract is changed as in [Conditional](conditional.md#contract) flow.
|
||||
The contract is changed as in [Conditional](conditional.md#contract) flow.
|
||||
|
||||
### Export data from for
|
||||
### Export data from `for`
|
||||
|
||||
The way to export data from `for` is the same as in [Conditional return](conditional.md#conditional-return) and [Race patterns](parallel.md#join-behavior).
|
||||
|
||||
```text
|
||||
```haskell
|
||||
xs: []string
|
||||
return: *string
|
||||
|
||||
@ -79,7 +76,7 @@ for x <- xs par:
|
||||
baz(return!5, return)
|
||||
```
|
||||
|
||||
### For on streams
|
||||
### `for` on streams
|
||||
|
||||
For on streams is one of the most complex and powerful parts of Aqua. See [CRDT streams](../crdt-streams.md) for details.
|
||||
`for` on streams is one of the most advanced and powerful parts of Aqua. See [CRDT streams](../crdt-streams.md) for details.
|
||||
|
||||
|
||||
@ -1,32 +1,31 @@
|
||||
# Parallel
|
||||
|
||||
Parallel execution is where everything becomes shiny.
|
||||
Parallel execution is where Aqua fully shines.
|
||||
|
||||
### Contract
|
||||
|
||||
Parallel arms have no access to each other's data. Sync points must be explicit \(see Join behavior\).
|
||||
|
||||
If any arm is executed successfully, the flow execution continues.
|
||||
|
||||
All the data defined in parallel arms is available in the subsequent code.
|
||||
* Parallel arms have no access to each other's data. Sync points must be explicit \(see [Join behavior](parallel.md#join-behavior)\).
|
||||
* If any arm is executed successfully, the flow execution continues.
|
||||
* All the data defined in parallel arms is available in the subsequent code.
|
||||
|
||||
### Implementation limitation
|
||||
|
||||
Parallel execution has some implementation limitations:
|
||||
|
||||
* Parallel means independent execution on different peers
|
||||
* No parallelism when executing a script on a single peer \(fix planned\)
|
||||
* No concurrency in services: one service instance does only one job simultaneously. Keep services small \(wasm limitation\)
|
||||
* No parallelism when executing a script on a single peer
|
||||
* No concurrency in services: every service instance does only one job simultaneously.
|
||||
* Keep services small in terms of computation and memory \(WebAssembly limitation\)
|
||||
|
||||
We might overcome these limitations later, but for now, plan your application design having this in mind.
|
||||
These limitations might be overcome in future Aqua updates, but for now, plan your application design having this in mind.
|
||||
|
||||
### Parallel operations
|
||||
|
||||
### par
|
||||
#### par
|
||||
|
||||
`par` syntax is derived from π-calculus notation of parallelism: `A | B`
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- foo and bar will be executed in parallel, if possible
|
||||
foo()
|
||||
par bar()
|
||||
@ -52,13 +51,13 @@ hello(x)
|
||||
par hello(y)
|
||||
```
|
||||
|
||||
`par` works in infix manner between the previously stated function and the next one.
|
||||
`par` works in an infix manner between the previously stated function and the next one.
|
||||
|
||||
#### co
|
||||
|
||||
`co` , short for `coroutine`, prefixes an operation to send it to background. From π-calculus perspective, it's the same as `A | null`, where `null`-process is the one that does nothing and completes instantly.
|
||||
`co` , short for `coroutine`, prefixes an operation to send it to the background. From π-calculus perspective, it's the same as `A | null`, where `null`-process is the one that does nothing and completes instantly.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Let's send foo to background and continue
|
||||
co foo()
|
||||
|
||||
@ -86,7 +85,7 @@ Join means that data was created by different parallel execution flows and then
|
||||
|
||||
In Aqua, you can refer to previously defined variables. In case of sequential computations, they are available, if execution not failed:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Start execution somewhere
|
||||
on peer1:
|
||||
-- Go to peer1, execute foo, remember x
|
||||
@ -105,7 +104,7 @@ baz(x, y)
|
||||
|
||||
Let's make this script parallel: execute `foo` and `bar` on different peers in parallel, then use both to compute `baz`.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Start execution somewhere
|
||||
on peer1:
|
||||
-- Go to peer1, execute foo, remember x
|
||||
@ -124,15 +123,15 @@ baz(x, y)
|
||||
|
||||
What will happen when execution comes to `baz`?
|
||||
|
||||
Actually, the script will be executed twice: first time it will be sent from `peer1`, and second time – from `peer2`. Or another way round: `peer2` then `peer1`, we don't know who is faster.
|
||||
Actually, the script will be executed twice: the first time it will be sent from `peer1`, and the second time – from `peer2`. Or another way round: `peer2` then `peer1`, we don't know who is faster.
|
||||
|
||||
When execution will get to `baz` for the first time, [Aqua VM](../../runtimes/aqua-vm.md) will realize that it lacks some data that is expected to be computed above in the parallel branch. And halt.
|
||||
When execution will get to `baz` for the first time, Aqua VM will realize that it lacks some data that is expected to be computed above in the parallel branch. And halt.
|
||||
|
||||
After the second branch executes, VM will be woken up again, reach the same piece of code and realize that now it has enough data to proceed.
|
||||
|
||||
This way you can express race \(see [Collection types](../types.md#collection-types) and [Conditional return](conditional.md#conditional-return) for other uses of this pattern\):
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Initiate a stream to write into it several times
|
||||
results: *string
|
||||
|
||||
|
||||
@ -4,21 +4,18 @@ By default, Aqua code is executed line by line, sequentially.
|
||||
|
||||
### Contract
|
||||
|
||||
Data from the first arm is available in the second branch.
|
||||
|
||||
Second arm is executed iff the first arm succeeded.
|
||||
|
||||
If any arm failed, then the whole sequence is failed.
|
||||
|
||||
If all arms executed successfully, then the whole sequence is executed successfully.
|
||||
* Data from the first arm is available in the second branch.
|
||||
* The second arm is executed if and only if the first arm succeeded.
|
||||
* If any arm failed, then the whole sequence is failed.
|
||||
* If all arms executed successfully, then the whole sequence is executed successfully.
|
||||
|
||||
### Sequential operations
|
||||
|
||||
#### call arrow
|
||||
|
||||
Any runnable piece of code in Aqua is an arrow from its domain to codomain.
|
||||
Any runnable piece of code in Aqua is an arrow from its domain to the codomain.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Call a function
|
||||
foo()
|
||||
|
||||
@ -32,13 +29,13 @@ y <- Peer.identify()
|
||||
z <- Op.identity(y)
|
||||
```
|
||||
|
||||
When you write `<-`, this means not just "assign results of the function on the right to variable on the left". It means that all the effects are executed: [service](../abilities-and-services.md) may change state, [topology](../topology.md) may be shifted. But you end up being \(semantically\) on the same peer where you have called the arrow.
|
||||
When you write `<-`, this means not just "assign results of the function on the right to variable on the left". It means that all the effects are executed: [service](../abilities-and-services.md) may change state, the [topology](../topology.md) may be shifted. But you end up being \(semantically\) on the same peer where you have called the arrow.
|
||||
|
||||
#### on
|
||||
|
||||
`on` denotes the peer where the code must be executed. `on` is handled sequentially, and the code inside is executed line by line by default.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo():
|
||||
-- Will be executed where `foo` was executed
|
||||
bar()
|
||||
@ -60,5 +57,5 @@ func foo():
|
||||
bar()
|
||||
```
|
||||
|
||||
See more in [Topology](../topology.md) section.
|
||||
See more in the [Topology](../topology.md) section.
|
||||
|
||||
|
||||
@ -6,7 +6,7 @@ An Aqua source file has a head and a body. The body contains function definition
|
||||
|
||||
The main way to import a file is via `import` expression:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
import "@fluencelabs/aqua-lib/builtin.aqua"
|
||||
|
||||
func foo():
|
||||
@ -17,7 +17,7 @@ Aqua compiler takes a source directory and a list of import directories \(usuall
|
||||
|
||||
Everything defined in the file is imported into the current namespace.
|
||||
|
||||
### `Use` Expression
|
||||
### `use` Expression
|
||||
|
||||
The `use` expression makes it possible to import a subset of a file, or to alias imports to avoid namespace collisions.
|
||||
|
||||
|
||||
@ -4,12 +4,11 @@ description: Define where the code is to be executed and how to get there
|
||||
|
||||
# Topology
|
||||
|
||||
Aqua lets developers describe the whole distributed workflow in a single script, link data, recover from errors, implement complex patterns like backpressure, and more. Hence, the network topology is at the heart of Aqua.
|
||||
|
||||
Aqua lets developers to describe the whole distributed workflow in a single script, link data, recover from errors, implement complex patterns like backpressure, and more. Hence, topology is at the heart of Aqua.
|
||||
Topology in Aqua is declarative: You just need to say where a piece of code must be executed, on what peer, and optionally how to get there. The Aqua compiler will add all the required network hops.
|
||||
|
||||
Topology in Aqua is declarative: You just need to say where a piece of code must be executed, on what peer, and optionally how to get there. he Aqua compiler will add all the required network hops.
|
||||
|
||||
### On expression
|
||||
## On expression
|
||||
|
||||
`on` expression moves execution to the specified peer:
|
||||
|
||||
@ -28,15 +27,15 @@ on myPeer:
|
||||
baz()
|
||||
```
|
||||
|
||||
### `%init_peer_id%`
|
||||
## `%init_peer_id%`
|
||||
|
||||
There is one custom peer ID that is always in scope: `%init_peer_id%`. It points to the peer that initiated this request.
|
||||
There is one custom peer ID that is always in scope: `%init_peer_id%`. It points to the peer that initiated this request.
|
||||
|
||||
{% hint style="warning" %}
|
||||
Using `on %init_peer_id%` is an anti-pattern: There is no way to ensure that init peer is accessible from the currently used part of the network.
|
||||
{% endhint %}
|
||||
|
||||
### More complex scenarios
|
||||
## More complex scenarios
|
||||
|
||||
Consider this example:
|
||||
|
||||
@ -44,22 +43,22 @@ Consider this example:
|
||||
func foo():
|
||||
on "peer foo":
|
||||
do_foo()
|
||||
|
||||
|
||||
func bar(i: i32):
|
||||
do_bar()
|
||||
|
||||
|
||||
func baz():
|
||||
bar(1)
|
||||
on "peer baz":
|
||||
foo()
|
||||
bar(2)
|
||||
bar(3)
|
||||
bar(3)
|
||||
```
|
||||
|
||||
Take a minute to think about:
|
||||
|
||||
* Where `do_foo` is executed?
|
||||
* Where `bar(1)` is executed?
|
||||
* Where is `do_foo` executed?
|
||||
* Where is `bar(1)` executed?
|
||||
* On what node `bar(2)` runs?
|
||||
* What about `bar(3)`?
|
||||
|
||||
@ -70,7 +69,7 @@ Declarative topology definition always works the same way.
|
||||
* `bar(2)` is executed on `"peer baz"`, despite the fact that foo does topologic transition. `bar(2)` is in the scope of `on "peer baz"`, so it will be executed there
|
||||
* `bar(3)` is executed where `bar(1)` was: in the root scope of `baz`, wherever it was called from
|
||||
|
||||
### Accessing peers `via` other peers
|
||||
## Accessing peers `via` other peers
|
||||
|
||||
In a distributed network it is quite common that a peer is not directly accessible. For example, a browser has no public network interface and you cannot open a socket to a browser at will. Such constraints warrant a `relay` pattern: there should be a well-connected peer that relays requests from a peer to the network and vice versa.
|
||||
|
||||
@ -81,12 +80,12 @@ Relays are handled with `via`:
|
||||
-- the compiler will add an additional hop to some relay
|
||||
on "some peer" via "some relay":
|
||||
foo()
|
||||
|
||||
|
||||
-- More complex path: first go to relay2, then to relay1,
|
||||
-- then to peer. When going out of peer, do it in reverse
|
||||
on "peer" via relay1 via relay2:
|
||||
foo()
|
||||
|
||||
|
||||
-- You can pass any collection of strings to relay,
|
||||
-- and it will go through it if it's defined,
|
||||
-- or directly if not
|
||||
@ -137,7 +136,7 @@ foo()
|
||||
|
||||
When the `on` scope is ended, it does not affect any further topology moves. Until you stop indentation, `on` affects the topology and may add additional topology moves, which means more roundtrips and unnecessary latency.
|
||||
|
||||
### Callbacks
|
||||
## Callbacks
|
||||
|
||||
What if you want to return something to the initial peer? For example, implement a request-response pattern. Or send a bunch of requests to different peers, and render responses as they come, in any order.
|
||||
|
||||
@ -150,7 +149,7 @@ func run(updateModel: Model -> (), logMessage: string -> ()):
|
||||
updateModel(m)
|
||||
par on "other peer":
|
||||
x <- getMessage()
|
||||
logMessage(x)
|
||||
logMessage(x)
|
||||
```
|
||||
|
||||
Callbacks have the [arrow type](types.md#arrow-types).
|
||||
@ -161,22 +160,22 @@ If you pass just ordinary functions as arrow-type arguments, they will work as i
|
||||
func foo():
|
||||
on "peer 1":
|
||||
doFoo()
|
||||
|
||||
|
||||
func bar(cb: -> ()):
|
||||
on "peer2":
|
||||
cb()
|
||||
|
||||
|
||||
func baz():
|
||||
-- foo will go to peer 1
|
||||
-- bar will go to peer 2
|
||||
bar(foo)
|
||||
bar(foo)
|
||||
```
|
||||
|
||||
If you pass a service call as a callback, it will be executed locally on the node where you called it. That might change.
|
||||
|
||||
Functions that capture the topologic context of the definition site are planned, not yet there. **Proposed** syntax:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func baz():
|
||||
foo = do (x: u32):
|
||||
-- Executed there, where foo is called
|
||||
@ -189,10 +188,10 @@ func baz():
|
||||
{% embed url="https://github.com/fluencelabs/aqua/issues/183" caption="Issue for adding \`do\` expression" %}
|
||||
|
||||
{% hint style="warning" %}
|
||||
Passing service function calls as arguments is very fragile as it does not track that a service is resolved in the scope of the call. Abilities variance may fix that.
|
||||
Passing service function calls as arguments is very fragile as it does not track that the service is resolved in the scope of the call. Abilities variance may fix that.
|
||||
{% endhint %}
|
||||
|
||||
### Parallel execution and topology
|
||||
## Parallel execution and topology
|
||||
|
||||
When blocks are executed in parallel, it is not always necessary to resolve the topology to get to the next peer. The compiler will add topologic hops from the par branch only if data defined in that branch is used down the flow.
|
||||
|
||||
@ -200,5 +199,3 @@ When blocks are executed in parallel, it is not always necessary to resolve the
|
||||
What if all branches do not return? Execution will halt. Be careful, use `co` if you don't care about the returned data.
|
||||
{% endhint %}
|
||||
|
||||
|
||||
|
||||
|
||||
@ -1,6 +1,6 @@
|
||||
# Types
|
||||
|
||||
### Scalars
|
||||
## Scalars
|
||||
|
||||
Scalar types follow the Wasm IT notation.
|
||||
|
||||
@ -12,24 +12,24 @@ Scalar types follow the Wasm IT notation.
|
||||
* Records \(product type\): see below
|
||||
* Arrays: see Collection Types below
|
||||
|
||||
### Literals
|
||||
## Literals
|
||||
|
||||
You can pass booleans \(true, false\), numbers, double-quoted strings as literals.
|
||||
|
||||
### Products
|
||||
## Products
|
||||
|
||||
```python
|
||||
```haskell
|
||||
data ProductName:
|
||||
field_name: string
|
||||
|
||||
|
||||
data OtherProduct:
|
||||
product: ProductName
|
||||
flag: bool
|
||||
flag: bool
|
||||
```
|
||||
|
||||
Fields are accessible with the dot operator `.` , e.g. `product.field`.
|
||||
Fields are accessible with the dot operator `.` , e.g. `product.field`.
|
||||
|
||||
### Collection Types
|
||||
## Collection Types
|
||||
|
||||
Aqua has three different types with variable length, denoted by quantifiers `[]`, `*`, and `?`.
|
||||
|
||||
@ -41,12 +41,11 @@ Appendable collection with 0..N values: `*`
|
||||
|
||||
Any data type can be prepended with a quantifier, e.g. `*u32`, `[][]string`, `?ProductType` are all correct type specifications.
|
||||
|
||||
|
||||
You can access a distinct value of a collection with `!` operator, optionally followed by an index.
|
||||
|
||||
Examples:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
strict_array: []u32
|
||||
array_of_arrays: [][]u32
|
||||
element_5 = strict_array!5
|
||||
@ -60,7 +59,7 @@ maybe_value: ?string
|
||||
value = maybe_value!
|
||||
```
|
||||
|
||||
### Arrow Types
|
||||
## Arrow Types
|
||||
|
||||
Every function has an arrow type that maps a list of input types to an optional output type.
|
||||
|
||||
@ -72,7 +71,7 @@ The absence of arguments is denoted `-> ()`.That is, this mapping takes no argum
|
||||
|
||||
Note that there's no `Unit` type in Aqua: you cannot assign a non-existing result to a value.
|
||||
|
||||
```python
|
||||
```haskell
|
||||
-- Assume that arrow has type: -> ()
|
||||
|
||||
-- This is possible:
|
||||
@ -82,24 +81,23 @@ arrow()
|
||||
x <- arrow()
|
||||
```
|
||||
|
||||
### Type Alias
|
||||
## Type Alias
|
||||
|
||||
For convenience, you can alias a type:
|
||||
|
||||
```python
|
||||
```haskell
|
||||
alias MyAlias = ?string
|
||||
```
|
||||
|
||||
### Type Variance
|
||||
## Type Variance
|
||||
|
||||
Aqua is made for composing data on the open network. That means that you want to compose things if they do compose, even if you don't control its source code.
|
||||
|
||||
Therefore Aqua follows the structural typing paradigm: if a type contains all the expected data, then it fits. For example, you can pass `u8` in place of `u16` or `i16`. Or `?bool` in place of `[]bool`. Or `*string` instead of `?string` or `[]string`. The same holds for products.
|
||||
|
||||
|
||||
For arrow types, Aqua checks the variance on arguments and contravariance on the return type.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- We expect u32
|
||||
xs: *u32
|
||||
|
||||
@ -130,36 +128,34 @@ bar(foo4)
|
||||
|
||||
Arrow type `A: D -> C` is a subtype of `A1: D1 -> C1`, if `D1` is a subtype of `D` and `C` is a subtype of `C1`.
|
||||
|
||||
### Type Of A Service And A File
|
||||
## Type Of A Service And A File
|
||||
|
||||
A service type is a product of arrows.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
service MyService:
|
||||
foo(arg: string) -> bool
|
||||
|
||||
|
||||
-- type of this service is:
|
||||
data MyServiceType:
|
||||
foo: string -> bool
|
||||
foo: string -> bool
|
||||
```
|
||||
|
||||
The file is a product of all defined constants and functions \(treated as arrows\). Type definitions in the file do not go to the file type.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- MyFile.aqua
|
||||
|
||||
func foo(arg: string) -> bool:
|
||||
...
|
||||
|
||||
|
||||
const flag ?= true
|
||||
|
||||
-- type of MyFile.aqua
|
||||
data MyServiceType:
|
||||
foo: string -> bool
|
||||
flag: bool
|
||||
flag: bool
|
||||
```
|
||||
|
||||
{% embed url="https://github.com/fluencelabs/aqua/blob/main/types/src/main/scala/aqua/types/Type.scala" caption="See the types system implementation" %}
|
||||
|
||||
|
||||
|
||||
|
||||
@ -6,7 +6,7 @@ Values in Aqua are backed by VDS \(Verifiable Data Structures\) in the runtime.
|
||||
|
||||
That's why values are immutable. Changing the value effectively makes a new one:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
x = "hello"
|
||||
y = "world"
|
||||
|
||||
@ -18,24 +18,24 @@ on "peer 1":
|
||||
|
||||
More on that in the Security section. Now let's see how we can work with values inside the language.
|
||||
|
||||
### Arguments
|
||||
## Arguments
|
||||
|
||||
Function arguments are available within the whole function body.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo(arg: i32, log: string -> ()):
|
||||
-- Use data arguments
|
||||
bar(arg)
|
||||
|
||||
|
||||
-- Arguments can have arrow type and be used as strings
|
||||
log("Wrote arg to responses")
|
||||
```
|
||||
|
||||
### Return values
|
||||
## Return values
|
||||
|
||||
You can assign results of an arrow call to a name, and use this returned value in the code below.
|
||||
You can assign the results of an arrow call to a name, and use this returned value in the code below.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Imagine a Stringify service that's always available
|
||||
service Stringify("stringify"):
|
||||
i32ToStr(arg: i32) -> string
|
||||
@ -47,7 +47,7 @@ func bar(arg: i32) -> string:
|
||||
-- Starting from there, you can use x
|
||||
-- Pass x out of the function scope as the return value
|
||||
<- x
|
||||
|
||||
|
||||
|
||||
func foo(arg: i32, log: *string):
|
||||
-- Use bar to convert arg to string, push that string
|
||||
@ -55,11 +55,11 @@ func foo(arg: i32, log: *string):
|
||||
log <- bar(arg)
|
||||
```
|
||||
|
||||
### Literals
|
||||
## Literals
|
||||
|
||||
Aqua supports just a few literals: numbers, quoted strings, booleans. You [cannot init a structure](https://github.com/fluencelabs/aqua/issues/167) in Aqua, only obtain it as a result of a function call.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- String literals cannot contain double quotes
|
||||
-- No single-quoted strings allowed, no escape chars.
|
||||
foo("double quoted string literal")
|
||||
@ -67,7 +67,7 @@ foo("double quoted string literal")
|
||||
-- Booleans are true or false
|
||||
if x == false:
|
||||
foo("false is a literal")
|
||||
|
||||
|
||||
-- Numbers are different
|
||||
-- Any number:
|
||||
bar(1)
|
||||
@ -79,11 +79,11 @@ bar(-1)
|
||||
bar(-0.2)
|
||||
```
|
||||
|
||||
### Getters
|
||||
## Getters
|
||||
|
||||
In Aqua, you can use a getter to peak into a field of a product or indexed element in an array.
|
||||
In Aqua, you can use a getter to peak into a field of a product or indexed element in an array.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
data Sub:
|
||||
sub: string
|
||||
|
||||
@ -91,7 +91,7 @@ data Example:
|
||||
field: u32
|
||||
arr: []Sub
|
||||
child: Sub
|
||||
|
||||
|
||||
func foo(e: Example):
|
||||
bar(e.field) -- u32
|
||||
bar(e.child) -- Sub
|
||||
@ -100,14 +100,13 @@ func foo(e: Example):
|
||||
bar(e.arr!) -- gets the 0 element
|
||||
bar(e.arr!.sub) -- string
|
||||
bar(e.arr!2) -- gets the 2nd element
|
||||
bar(e.arr!2.sub) -- string
|
||||
bar(e.arr!2.sub) -- string
|
||||
```
|
||||
|
||||
Note that the `!` operator may fail or halt:
|
||||
|
||||
* If it is called on an immutable collection, it will fail if the collection is shorter and has no given index; you can handle the error with [try](operators/conditional.md#try) or [otherwise](operators/conditional.md#otherwise).
|
||||
* If it is called on an appendable stream, it will wait for some parallel append operation to fulfill, see [Join behavior](operators/parallel.md#join-behavior).
|
||||
|
||||
* If it is called on an immutable collection, it will fail if the collection is shorter and has no given index; you can handle the error with [try](https://github.com/fluencelabs/aqua-book/tree/4177e00f9313f0e1eb0a60015e1c19a956c065bd/language/operators/conditional.md#try) or [otherwise](https://github.com/fluencelabs/aqua-book/tree/4177e00f9313f0e1eb0a60015e1c19a956c065bd/language/operators/conditional.md#otherwise).
|
||||
* If it is called on an appendable stream, it will wait for some parallel append operation to fulfill, see [Join behavior](https://github.com/fluencelabs/aqua-book/tree/4177e00f9313f0e1eb0a60015e1c19a956c065bd/language/operators/parallel.md#join-behavior).
|
||||
|
||||
{% hint style="warning" %}
|
||||
The `!` operator can currently only be used with literal indices.
|
||||
@ -115,12 +114,11 @@ That is,`!2` is valid but`!x` is not valid.
|
||||
We expect to address this limitation soon.
|
||||
{% endhint %}
|
||||
|
||||
### Assignments
|
||||
## Assignments
|
||||
|
||||
Assignments, `=`, only give a name to a value with applied getter or to a literal.
|
||||
Assignments, `=`, only give a name to a value with an applied getter or to a literal.
|
||||
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo(arg: bool, e: Example):
|
||||
-- Rename the argument
|
||||
a = arg
|
||||
@ -130,13 +128,13 @@ func foo(arg: bool, e: Example):
|
||||
c = "just string value"
|
||||
```
|
||||
|
||||
### Constants
|
||||
## Constants
|
||||
|
||||
Constants are like assignments but in the root scope. They can be used in all function bodies, textually below the place of const definition. Constant values must resolve to a literal.
|
||||
|
||||
You can change the compilation results with overriding a constant but the override needs to be of the same type or subtype.
|
||||
You can change the compilation results by overriding a constant but the override needs to be of the same type or subtype.
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- This flag is always true
|
||||
const flag = true
|
||||
|
||||
@ -150,7 +148,7 @@ func bar():
|
||||
foo(setting)
|
||||
```
|
||||
|
||||
### Visibility scopes
|
||||
## Visibility scopes
|
||||
|
||||
Visibility scopes follow the contracts of execution flow.
|
||||
|
||||
@ -158,10 +156,10 @@ By default, everything defined textually above is available below. With some exc
|
||||
|
||||
Functions have isolated scopes:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo():
|
||||
a = 5
|
||||
|
||||
|
||||
func bar():
|
||||
-- a is not defined in this function scope
|
||||
a = 7
|
||||
@ -170,20 +168,20 @@ func bar():
|
||||
|
||||
[For loop](flow/iterative.md#export-data-from-for) does not export anything from it:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
func foo():
|
||||
x = 5
|
||||
for y <- ys:
|
||||
-- Can use what was defined above
|
||||
z <- bar(x)
|
||||
|
||||
|
||||
-- z is not defined in scope
|
||||
z = 7
|
||||
z = 7
|
||||
```
|
||||
|
||||
[Parallel](flow/parallel.md#join-behavior) branches have [no access](https://github.com/fluencelabs/aqua/issues/90) to each other's data:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- This will deadlock, as foo branch of execution will
|
||||
-- never send x to a parallel bar branch
|
||||
x <- foo()
|
||||
@ -193,28 +191,27 @@ par y <- bar(x)
|
||||
baz(x, y)
|
||||
```
|
||||
|
||||
Recovery branches in [conditional flow](operators/conditional.md) have no access to the main branch as the main branch exports values, whereas the recovery branch does not:
|
||||
Recovery branches in [conditional flow](https://github.com/fluencelabs/aqua-book/tree/4177e00f9313f0e1eb0a60015e1c19a956c065bd/language/operators/conditional.md) have no access to the main branch as the main branch exports values, whereas the recovery branch does not:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
try:
|
||||
x <- foo()
|
||||
otherwise:
|
||||
-- this is not possible – will fail
|
||||
bar(x)
|
||||
y <- baz()
|
||||
|
||||
|
||||
-- y is not available below
|
||||
willFail(y)
|
||||
|
||||
willFail(y)
|
||||
```
|
||||
|
||||
### Streams as literals
|
||||
## Streams as literals
|
||||
|
||||
Stream is a special data structure that allows many writes. It has [a dedicated article](crdt-streams.md).
|
||||
|
||||
To use a stream, you need to initiate it at first:
|
||||
|
||||
```text
|
||||
```haskell
|
||||
-- Initiate an (empty) appendable collection of strings
|
||||
resp: *string
|
||||
|
||||
@ -225,13 +222,13 @@ par resp <- bar()
|
||||
for x <- xs:
|
||||
-- Write to a stream that's defined above
|
||||
resp <- baz()
|
||||
|
||||
|
||||
try:
|
||||
resp <- baz()
|
||||
otherwise:
|
||||
on "other peer":
|
||||
resp <- baz()
|
||||
|
||||
|
||||
-- Now resp can be used in place of arrays and optional values
|
||||
-- assume fn: []string -> ()
|
||||
fn(resp)
|
||||
@ -239,7 +236,7 @@ fn(resp)
|
||||
-- Can call fn with empty stream: you can use it
|
||||
-- to construct empty values of any collection types
|
||||
nilString: *string
|
||||
fn(nilString)
|
||||
fn(nilString)
|
||||
```
|
||||
|
||||
One of the most frequently used patterns for streams is [Conditional return](flow/conditional.md#conditional-return).
|
||||
|
||||
Loading…
Reference in New Issue
Block a user