Compiler flags for Haskell

[Bubbler-4]

A couple of days ago, I tried giving -O GHC option in CW kumite like this:

{-# OPTIONS_GHC -O #-}

But the compiler rejected it, saying that -O is ignored because --interactive is on. (I used it in Preloaded section, and didn't check other sections yet.)

The --interactive flag is usually just for running ghci and (if I'm understanding the GHC docs correctly) not for use in compiled programs. That's pretty lame because GHC's optimization is really good if enabled (it's sometimes said that Haskell is almost on par with C/C++ about performance, at least if properly coded) but we're totally throwing it away and dragging it down to that of common interpreted languages.

That said, can you show us the current GHC command-line options for v8? Let's see what we can change to make it better.

[kazk]

That said, can you show us the current GHC command-line options for v8? Let's see what we can change to make it better.

stack runghc -- -i/path/to/include:src:test test/Main.hs

test/Main.hs

module Main where

import Test.Hspec.Runner
import Test.Hspec.Formatters.Qualified (codewars)

import qualified Spec

main :: IO ()
main = hspecWith defaultConfig {configFormatter = Just codewars} Spec.spec

test/Spec.hs

{-# OPTIONS_GHC -F -pgmF hspec-discover -optF --module-name=Spec #-}

[Bubbler-4]

runghc seems to assume --interactive, and there's no way to fix it easily. I guess ghc --make then running the output file is the way to go - something close to how to run a C project in CW.

For -i/path/to/include:src:test, -isrc:test should work unless you really have a dependency in /path/to/include literally.

Here's what I use in my own project (I don't use stack):

ghc --make -isrc:test test/Spec.hs -o out/Spec
out/Spec

Given that you do use stack and a separate Main, something like this would fit the needs:

stack ghc -- --make -isrc:test test/Main.hs -o a.out && a.out

I don't think we should actually include any fancy flags on the script, as anyone (be a kata author or solver) can include any flags via OPTIONS_GHC to fit their needs.

[kazk]

For -i/path/to/include:src:test, -isrc:test should work unless you really have a dependency in /path/to/include literally.

It includes the folder where the formatter and hspec-codewars is. I just changed the actual path to /path/to/include.

I don't think we should actually include any fancy flags on the script, as anyone (be a kata author or solver) can include any flags via OPTIONS_GHC to fit their needs.

I took them from Hspec discover example. Not sure which one is necessary or what each of them means.

[Bubbler-4]

It includes the folder where the formatter and hspec-codewars is.

Ah, that makes sense.

Not sure which one is necessary or what each of them means.

I didn't mean that one, the test/Spec.hs file is perfectly fine as is. By "the script", I meant the build script i.e. the one with stack runghc -- ... or stack ghc -- .... Also the "fancy flag" means optimizations, warnings, language extensions etc.

[kazk]

Got it working. I'll let you know when I deploy it.

[Bubbler-4]

Probably we need to test-run some proof katas to see if they don't timeout while compiling. Especially A+B=B+A one is known for being tight (not sure on other ones). It's not yet v8-enabled, so I guess we can check it while moving it to v8 (though I just found it's not yet unlocked for editing...)

[kazk]

This is deployed now.

[Bubbler-4]

Umm... Looks like the running time display in V8 (the thing that comes with <COMPLETEDIN::>) has disappeared (V7 is ok, as expected). Can you check the possible causes?

[kazk]

I removed the outer most "Tests" group (#655) which was used to calculate it. I haven't found a way to add duration for each describe yet.

[Bubbler-4]

Did some search and my wild guess is that main = hspecWith {-option-} $ mapSpecItem timeIt id spec might work, with Test.Hspec.Core.Spec.mapSpecItem and System.TimeIt.timeIt from package timeit or the simplified version

timeIt ioa = do
  t1 <- getCPUTime
  ioa
  t2 <- getCPUTime
  printf "%.3fs" (t2 - t1)

I'll try it out in a kumite later.