README.md

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Overview

yerevan.rs is a computation expressions (do-notations) library for Rust, inspired by F#'s CEs, but with changes and improvements in syntax-design.

Docs

1. Firstly define the struct which is implementing all the neccessary functions for yerevan.rs's computation expressions. Like this:

struct SimpleBinder {}
impl SimpleBinder {
    pub fn bind<T, U>(val: Option<T>, f: &dyn Fn(T) -> Option<U>) -> Option<U> {
        match val {
            Some(v) => f(v),
                None => SimpleBinder::zero(),
        }
    }
    pub fn ret<T>(val: T) -> Option<T> {
        Some(val)
    }
    pub fn zero<T>() -> Option<T> {
        None
    }
}

2. And then use your struct as computation expression type in yer! macro. Like this:

yer! {
    SimpleBinder =>
    let! ...
    let ...
    ret ...
}

yer! expression	description
$your_struct =>	Defines the struct as the provider of computation expression functions.
let $your_var = $your_expression	Uses the last defined struct in macros as the provider of bind function and calls the $that_struct::bind($your_expression, &|$your_var| { next code }) expression.
let $your_var = $your_expression	Defines the variable $your_var
do! $your_expression	Uses the last defined struct in macros as the provider of bind function and calls the $that_struct::bind($your_expression, &|_| { next code }) expression.
do $your_expression	Simply runs $your_expression
ret! $your_expression	Uses the last defined struct in macros as the provider of ret_from function and calls the $that_struct::ret_from($your_expression) expression.
ret $your_expression	Uses the last defined struct in macros as the provider of ret function and calls the $that_struct::ret($your_expression) expression.
yield $your_expression	Uses the last defined struct in macros as the provider of combine and ret_yield functions and calls the $that_struct::combine(yer!($that_struct => next code, $that_struct::ret_yield($your_expression)) expression.

Examples

For now examples are available in /tests directory in repository. GH-link: https://github.com/marat0n/yerevan.rs/blob/dev/tests/common.rs

Roadmap (+ mini changelog)

The linked ones are done, they are linked to the crates.io/crates/yerevan page to the version where this roadmap-point was done. Not linked points are the plan for future updates.

• 0.1
  • yer! macro:
    • some_struct => expression to create the specified structure context where all next expressions of that CE will be executed using methods of this structure (in FP that kind of structures are called monads);
    • let! expression executed by bind<T, U>: (val: T, fn: (T) -> U) -> U method in your defined struct (monad);
    • let expression (just define what you want without breaking the CE);
    • do! expression executed the same as let! but returned value from bind method is ignored;
    • do expression (just do what you want without breaking the CE);
    • ret! expression executed by ret_from<T>: (val: T) -> T method in your defined struct (monad);
    • ret expression executed by ret<T, W<T>>: (val: T) -> W<T> method in your defined struct (monad);
    • yield expression executed by combine<T, W<T>>: (val1: W<T>, val2: T) -> W<T> where val1-parameter is used for all next code in CE and val2-parameter is used for executing ret_yield<T, U>: (val: T) -> U.
  • initial tests, examples, docs.
• 0.2
  • upgrade yer! macro:
    • add implentation for methods: Run, YieldFrom, Zero from F#'s CE-types;
    • add expressions to macro: yeild!, if ... else, if! ... else!.
  • create default CEs for Option and Result types.
• 0.3
  • upgrade yer! macro:
    • add ability assign your instructions to some operators inside yer macro.