Not a very descriptive subject, I know, but here's what I'd like to do. I can take getChar and create an infinate list:
listChars = getChar : listChars
but how do I go about creating a finite list, e.g. a list that ends as
soon as 'q' is pressed?
I was thinking of something like
listChars1 = do
c <- lift getChar
if c == 'q'
then [return c]
else [return c] ++ listChars1
However, that triggers an interesting behaviour in ghci:
*Main> :t listChars1
<interactive>:1:0:
Can't find interface-file declaration for listChars1
Probable cause: bug in .hi-boot file, or inconsistent .hi file
Use -ddump-if-trace to get an idea of which file caused the error
Compiling it doesn't work either:
% ghc -o listio listio.hs
listio.o: In function `Main_main_info':
(.text+0x1bd): undefined reference to `Main_listChars1_closure'
listio.o: In function `Main_main_srt':
(.rodata+0x10): undefined reference to `Main_listChars1_closure'
collect2: ld returned 1 exit status
I was also looking briefly at ListT, bout couldn't quite see how to use
basic list operations on it, e.g. ':' '++' etc.
listChars2 :: ListT IO Char
listChars2 = do
c <- lift getChar
if c == 'q'
then lift $ return c
else (lift $ return c) ++ listChars2
/M
--
Magnus Therning (OpenPGP: 0xAB4DFBA4)
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