Here is the list of twenty questions I had about Haskell lexical and syntax
structure which I presented to the East Anglia Workshop in September. I didn't
get a great deal of consensus then, and talking to Ian Holyer (who had a
similar
list) today, I'm reminded to submit them to further scrutiny.
Most of them revolve around the transition into and out of various different
lexically determined parts of the language; in particular free-form and
layout (although I also use comment and string tokenization quite a bit).
So which of the following twenty programs are syntactically legal 1.2 (or 1.3)
Haskell programs, and why?
Answers next week,
---
David Lester, Dept CS, Manchester University, Manchester M13 9PL UK.
-- begin 1 --
-- end 1 --
-- begin 2 --
{}
-- end 2 --
-- begin 3 --
main = print "\'"
-- end 3 --
-- begin 4 --
main = print '\"'
-- end 4 --
-- begin 5 --
main = print "5\
\\n"
-- end 5 --
-- begin 6 --
s = "6\
\\n"
main = print s
-- end 6 --
-- begin 7 --
main = print ("#" ++ "7\n")
-- end 7 --
-- begin 8 --
main = print s where {s = case () of _ -> "8\n"}
-- end 8 --
-- begin 9 --
main = print s where {s = case () of _ -> "9\n"
}
-- end 9 --
-- begin 10 --
main = let {s=t where
t = "10\n"} in print s
-- end 10 --
-- begin 11 --
main = let {s=t where
t = "11\n"} in print s
-- end 11 --
-- begin 12 --
main = let {s=t where
t = "12\n"}
in print s
-- end 12 --
-- begin 13 --
main = let {s=t where
t = "12\n"} {-
-} in print s
-- end 13 --
-- begin 14 --
main = print s
s = if True then case () of "14\n" else "error\n"
-- end 14 --
-- begin 15 --
main = case "" of (x:xs) -> "error\n"
[] -> case () of
_ -> print "15\n"
-- end 15 --
-- begin 16 --
main = case "" of (x:xs) -> "error\n"
[] -> case () of
_ -> print "16\n"
-- end 16 --
-- begin 17 --
main = case "" of [] -> case () of
_ -> print "17\n" (x:xs) -> "error\n"
-- end 17 --
-- begin 18 --
main = case "" of (x:xs) -> "error\n" {-
-} [] -> "18\n"
-- end 18 --
-- begin 19 --
main = print "19\n"
module A where
loop = loop
-- end 19 --
-- begin 20 --
module Main where
main = print "20\n"
module A where
loop = loop
-- end 20 --
