The function which divides its argument by 2
The function which divides its argument by 2
map((x) => x/2, [1,2,3,4])
==> [0,1,1,2]
(In rex, division is integer division (truncating) unless one of the arguments is floating point, in which case the result is too.)
In general:
(X) Þ some expression E
is read:
"The function which, with argument X, returns the value of E".
E will usually contain X, although it need not:
(X) Þ 5
is the function which yields 5 regardless of argument.
map((x) Þ 5, [1,2,3,4]) ==> [5,5,5,5]
map is called "higher-order" because it is a function taking a function as its argument