README.md

assertion

branch	status
master
develop

Assertion with condition string representation in Haskell

Install

Add this library to your stack.yaml like the following if you use Stack.

...
extra-deps:
- git: https://github.com/nwtgck/assertion-haskell.git
  commit: 4340a96555606d590d54669b9ae992a5b8c9a10d
...

Then, add assertion to your package.yaml.

...
library:
 dependencies:
 - assertion
...

Usages

assert

{-# LANGUAGE QuasiQuotes #-}

import Assertion

main :: IO ()
main = do
  let a = "hello"
  let b = 10
  let !x = [assert|a == "hello" && b > 9999999|]
  
  putStrLn "End!"

ExampleMain.hs: Assertion failed: 'a == "hello" && b > 9999999'

staticAssert

Assert in compile time. So code bellow should be compile error.

{-# LANGUAGE TemplateHaskell #-}

import Assertion

-- NOTE: Compile error (Good!)
main :: IO ()
main = do
  -- NOTE: Compile error (Good!)
  let _ = $(staticAssert (length "hello" == 99999))  
  
  putStrLn "End!"

Compile error will happen. Good!

examples/StaticAssertExample.hs:9:13: error:
    • Compile time assertion failed
    • In the untyped splice: $(staticAssert (length "hello" == 99999))
  |
9 |   let _ = $(staticAssert (length "hello" == 99999))
  |