Just a silly thing that's been nagging me. a very common way (at least
in the base libraries) of formatting function types seems to be this:
hPutBuf :: Handle -- handle to write to
-> Ptr a -- address of buffer
-> Int -- number of bytes of data in buffer
-> IO ()
I remember when I first started learning Haskell, and these many-arrowed
functions seemed very strange to me: "Okay, we give it a handle, and get
a pointer, and, um, from this we get an int, and from this an action?
Er?"
The problem here is that the first parameter has a distinguished look
while the other parameters and the return value all look the same. I
think that a naive reader is inclined to assume that line breaks are
situated at major structural boundaries. Consider two different
interpretations of the structure of the type term:
(((Handle (Handle
-> Ptr a) ->(Ptr a
-> Int) ->(Int
-> IO ()) -> IO ())))
Which looks more natural?
The point of this rant is just this: the aforementioned multi-line
formatting style should only be used for left-associative infix
operators. For right-associative ones (such as the function arrow), the
One True Way is this:
Handle ->
Ptr a ->
Int ->
IO ()
Nuff said.
Lauri Alanko
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