[Haskell-cafe] unexpected compiler behavior

jepalomar23 at ono.com jepalomar23 at ono.com
Tue Dec 5 06:07:07 EST 2006

I am newbie in Haskell and do not understand why the interpreted mode
differs from the compiled program.
I run this code
main =  do 
          putStr "line1"
          putStr "line2"
          return (x++y)

either under runhugs or runghc or in a console under ghci and works
properly, that is, first displays "line1"  and then prompts for the
corresponding inputs through the keyboard, and so on. However, if I
compile the code with the command line 
ghc --make Main.hs -o main
and launch the compiled program main, then at first prompts for the 
input lines through the keyboard and then displays the strings "line1"
I have read in the tutorials that the command "do" implies an ordered
execution and this only occurs in interpreted mode.
Using the monadic notation >> , >>= occurs the same unordered behavior.
¿How can I avoid the unordered execution of this code in a compiled
Thanks in advance.

More information about the Haskell-Cafe mailing list