Martijn van Steenbergen
On 8/2/10 7:09, Ertugrul Soeylemez wrote:
Given the definition of a Haskell function, Haskell is a pure language. The notion of a function in other languages is not:
int randomNumber();
The result of this function is an integer. You can't replace the function call by its result without changing the meaning of the program.
I'm not sure this is fair. It's perfectly okay to replace a call "randomNumber()" by that method's *body* (1), which is what you argue is okay in Haskell.
This is not the same. In Haskell you can replace the function call by its /result/, not its body. You can always do that. But the result of an IO-based random number generator is an IO computation, not a value. It's not source code either, and it's not a function body. It's a computation, something abstract without a particular representation. This is what referential transparency is about. Not replacing function calls by function bodies, but by their /results/. In C you can't replace putchar(33) by 33 because that changes the program. Of course there are some exceptions like many functions from math.h. Unlike Haskell you don't write a program by using a DSL (like the IO monad), but you encode it directly as a series of statements and function calls. C has no notion of a "computation" the same way Haskell has. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/