ghci

While doing some exercises in GHCi I typed and got the following> ghci> (1 "one") <interactive>:187:1: No instance for (Num ([Char] -> a0)) arising from a use of ‘it’ In a stmt of an interactive GHCi command: print it which is an error, howeve if I ask GHCi for the type of the expression it does not give any error: ghci> :type (1 "one") (1 "one") :: Num ([Char] -> t) => t What is the meaning of (1 "one") ? Why does this expression gives an error, but GHCi tells it is well typed? What is the meaning of Num ([Char] -> t) => t ? Thanks. Haskell Report to the rescue! (Quoting section 6.4.1 ) An

When using the interactive GHC interpreter, it's possible to ask for the inferred type of an expression: Prelude> :t map map :: (a -> b) -> [a] -> [b] It seems that it takes the names of the type variables from the signature since map is defined as map :: (a -> b) -> [a] -> [b] map _ [] = [] map f (x:xs) = f x : map f xs in the Prelude. That makes a lot of sense! My question is: how are type variable names picked when there is no signature given? An example would be Prelude> :t map fst map fst :: [(b, b1)] -> [b] where it picked names b and b1 . It's clear that renaming must take place, but

I'm used to debug my code using ghci. Often, something like this happens (not so obvious, of course): ghci> let f@(_:x) = 0:1:zipWith(+)f x ghci> length f Then, nothing happens for some time, and if I don't react fast enough, ghci has eaten maybe 2 GB of RAM, causing my system to freeze. If it's too late, the only way to solve this problem is [ALT] + [PRINT] + [K]. My question: Is there an easy way to limit the memory, which can be consumed by ghci to, let's say 1 GB? If limit is exceed, the calculation should ve aborted or ghci should be killed. Bas Bossink A platform independant way to

Consider the following program. It runs forever and does nothing useful, but the memory consumption in ghci is constant : --NoExplode.hs module Main (main) where test :: [Int] -> IO() test lst = do print "test" rList lst rList :: [Int] -> IO () rList [] = return () rList (x:xs) = do rList xs main = do test [1..] Now consider the following trivially modified version of the above. When this program is run in ghci the memory explodes. The only difference is that print "test" is now assigned to x in the do block of test . --Explode.hs module Main (main) where test :: [Int] -> IO() test lst = do x

Haskell Stack Overflow layout preprocessor module StackOverflow where -- yes, the source of this post compiles as is Skip down to What to do to get it working if you want to play with this first (1/2 way down). Skip down to What I would like if I witter on a bit and you just want to find out what help I'm seeking. TLDR Question summary: Can I get ghci to add filename completion to the :so command I defined in my ghci.conf ? Could I somehow define a ghci command that returns code for compilation instead of returning a ghci command, or does ghci instead have a better way for me to plug in