GHC and CPP

[chb hemma]

Hello.

I'm using:
> ghc -V
The Glorious Glasgow Haskell Compilation System, version 6.12.3

I'm trying to do an ASSERT makro for my Haskell test programs but I have
no luck with the stringizing operator # of cpp. This code:

#define STRINGIZE(x) #x
#define ASSERT_EQUALS(e,r) (if e==r then return () else putStrLn $
"Error: " ++ STRINGIZE(e))

main = do ASSERT_EQUALS(1,2)

compiling with:

> ghc -XCPP testPP.hs

fails with:

testPP.hs:4:63: parse error on input `#'

Using the cpp on the file produces expected results (no # char but value
of arg e put in quotes):
> cpp testPP.hs
# 1 "testPP.hs"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "testPP.hs"

main = do (if 1==2 then return () else putStrLn $ "Error: " ++ "1")

Compiling with ghc and the -E flag gives on the other hand:

> ghc -XCPP -E testPP.hs
> cat testPP.hspp

{-# LINE 1 "testPP.hs" #-}
# 1 "testPP.hs"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "testPP.hs"

main = do (if 1==2 then return () else putStrLn $ "Error: " ++ #1)

Why is it expanded differently?

[chb hemma]

Solved it by removing my STRINGIZE macro and put the argument in the
string. It seems cpp is not the preprocessor used when specifying -XCPP
to ghc.

new code:

#define ASSERT_EQUALS(e,r) (if e==r then return () else putStrLn $

"Error: e")

replaces: