Every multi parameter function can be thought of accepting a single parameter
and returning a partial function. Example, consider a sum function which
accepts two numbers and returns the result.
sum(2, 3) -> 5 (Return type number)
But if only one argument is passed to the sum function, the return type would
instead be a function.
sum(2) -> Function(partial) which accepts 1 argument and returns a number
While I was aware of this technique in javascript, but never thought that the
concept could be generalized to any function.
Composing
Multiple functions can be composed together to make new functions. Example,
f = square . plus1
Assuming square squares a number and plus adds 1 to a number, the new
function f would perform these two operations on any given number. So the
following would be true:
f(2) = 5
The . is the compose operator in Haskell. The idea is to write very simple
functions and combine them together to make more complex functions.
Any binary function can be written in infix notation
Haskell doesn't have a mod operator like %. Instead there is a function
called mod which accepts two parameters. In Haskell, it can be written in
both infix and prefix mode. The following two statements are equivalent.
5 mod 2
mod 5 2
Infinite Lists
Writing [1..] is a unbounded list. Calling length on such a list will hang
the computer. But we can perform other array operations like head, take
without causing infinite recursion. Haskell evaluates the infinite list lazily
as much as it needs to.
Currying
Every multi parameter function can be thought of accepting a single parameter and returning a partial function. Example, consider a
sumfunction which accepts two numbers and returns the result.But if only one argument is passed to the
sumfunction, the return type would instead be a function.While I was aware of this technique in javascript, but never thought that the concept could be generalized to any function.
Composing
Multiple functions can be composed together to make new functions. Example,
Assuming
squaresquares a number andplusadds 1 to a number, the new functionfwould perform these two operations on any given number. So the following would be true:The
.is the compose operator in Haskell. The idea is to write very simple functions and combine them together to make more complex functions.Any binary function can be written in infix notation
Haskell doesn't have a
modoperator like%. Instead there is a function calledmodwhich accepts two parameters. In Haskell, it can be written in both infix and prefix mode. The following two statements are equivalent.Writing
[1..]is a unbounded list. Callinglengthon such a list will hang the computer. But we can perform other array operations likehead,takewithout causing infinite recursion. Haskell evaluates the infinite list lazily as much as it needs to.