On Thu, 2009-05-28 at 01:45 +0400, Bulat Ziganshin wrote:
for me, it was better than ghc errmsg. main thing is that i don't feel automatically what is expected and what is inferred. here Hugs says that True is Bool and the remaining is Int, so i "feel" the situation
I absolutely agree about expected/inferred. I always forget which is which, because I can figure both could apply to each. Say, in this simple example:
Prelude> let f = (+5) Prelude> f "abc"
<interactive>:1:2: Couldn't match expected type `Integer' against inferred type `[Char]' In the first argument of `f', namely `"abc"' In the expression: f "abc" In the definition of `it': it = f "abc"
Does expected mean that, based on the type signature, it should be an Integer, or based on the argument that I provided, it should be a String? The same goes for the inferred type: it knows what the type of the literal argument (String), so I would assume the inferred type was the type in the function's signature. Unfortunately, my reasoning in both cases can go the wrong way . . . Better language may be much more helpful, although I'm not sure what may be easier to interpret. Jeff Wheeler