Get absolute path of current source file in Haskell

Question

Is it possible to get the absolute path of the current source file in Haskell?

I could only find one relevant function: getCurrentDirectory from System.Directory, but it "returns an absolute path to the current directory of the calling process.", not the path of the current file.

(I need it to read sample inputs which are located in the same folder as the source file; If there's any better way to do it, that will be helpful too!)

Answer 1

You can use CPP. If you compile this file

{-# LANGUAGE CPP #-}
main = print __FILE__

it will print the path to the source as you passed it to ghc – which may or may not be the full path, though:

/tmp $ ghc --make mypath.hs 
[1 of 1] Compiling Main             ( mypath.hs, mypath.o )
Linking mypath ...
/tmp $ ./mypath 
"mypath.hs"
/tmp $ ghc --make /tmp/mypath.hs 
Linking /tmp/mypath ...
/tmp $ ./mypath 
"/tmp/mypath.hs"

Answer 2

As an alternative, the file-embed package can be used here. It uses template haskell to embed files/directories.

This can be very useful to embed resources or configs in the executable. It may not be advisable to read the sample input this way though. data-files in cabal might be better alternative as already pointed out earlier in this thread.