On Wed, Mar 4, 2009 at 12:25 PM, Michael Easter wrote:

Folks,

I have a simple type called Beverage and an example that allows me to construct Maybe Beverage types.

Here are some type signatures for example functions:

request :: String -> Maybe Beverage

addMalt :: Beverage -> Maybe Beverage

I have defined a chain function like so:

chain :: (Maybe a) -> (a -> Maybe b) -> (Maybe b) chain = (>>=)

I can do this:

(chain (request "beer") addMalt)

and

request "beer" `chain` addMalt

I think I understand why, as I use the back-ticks for infix.

However, I don't have to do that for the true bind function, (>>=)

request "beer" >>= addMalt

I would like to use chain in this way -- that is without back-ticks.  I'm not sure how...

Is there something I'm missing?

Yes, there are certain function names that allow infix usage without the back-ticks, the name 'chain' doesn't. What those function names are? Roughly you can say that functions that they are functions that look like binary operations, like + - ++ >>> etc. I'm not sure I read the pangauage spec correctly, but it looks like operators are made up of the following characters !@#$%^&*+-./\|<=>?~ (IIRC ':' has a special meaning in that it's allowed in "constructors", cf 1:2:[]). /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe

Am Mittwoch, 4. März 2009 13:25 schrieb Michael Easter:

Folks,

I have a simple type called Beverage and an example that allows me to construct Maybe Beverage types.

Here are some type signatures for example functions:

request :: String -> Maybe Beverage

addMalt :: Beverage -> Maybe Beverage

I have defined a chain function like so:

chain :: (Maybe a) -> (a -> Maybe b) -> (Maybe b) chain = (>>=)

I can do this:

(chain (request "beer") addMalt)

and

request "beer" `chain` addMalt

I think I understand why, as I use the back-ticks for infix.

However, I don't have to do that for the true bind function, (>>=)

request "beer" >>= addMalt

I would like to use chain in this way -- that is without back-ticks. I'm not sure how...

You can't. Haskell has (infix) operators, whose names are composed of symbols (>, <, |, :, +, ...) and (prefix) functions, whose names are composed of letters, underscores (_) and primes ('). If you want to use a function infix or an operator prefix, you must indicate that to the compiler, which is done by enclosing a function name in backticks or an operator symbol in parentheses. If you could use a function name infix or prefix without indicating which you want, what would id const even be? Should it be id `const` even or (id const) even?

Is there something I'm missing?

thanks Mike

ps. Thanks to everyone for the great discussion on IO (re: previous question)