On 10/1/07, PR Stanley
f x = x + x Is the "x" use to create a pattern in the definition and when f is called it's replaced by a value?
Those equation-like definitions are syntactic sugar for lambda abstractions. f could as well be defined as f = \x -> x + x.
Please elaborate
First, the f x = part says that f is a function which takes a single parameter, called x. The other side of the = sign gives the function body: in this case, x + x. This is exactly the same thing that is expressed by the lambda expression \x -> x + x This expression defines a function that takes a single parameter called x, and returns the value of x + x. The only difference is that with the lambda expression, this function is not given a name. But you can easily give the function a name (just as you can give any Haskell expression a name) by writing f = \x -> x + x In general, writing g x y z = blah blah is just a shorthand for g = \x -> \y -> \z -> blah blah. That is, it simultaneously creates a function expression, and assigns it a name. Does that help? -Brent