Maps, Functions

ISETL has many pre-defined functions, but the user may also define her/his own functions.

A func is the computational representation of a function, as a map is the ordered pair representation, and a tuple is the sequence representation.

Example
>  f := func(x);  $ The square function.
>>    return x*x;
>>  end;
>  f(-3); f(0); f(5); f(3.25);
9;
0;
25;
10.563
>

Example
>  os := func(p,q);  $ Product of permutations.
>>    if #p = #q then
>>      return [(q(i)) : i in [1..#p] ];
>>    end if;
>>  end func;
>  x := [1,3,2];
>  y := [3,1,2];
>  os(x,y);  $ os is a function of two variables
[2, 1, 3];
>  x .os y;  $ Note the dot (alternate notation).
[2, 1, 3];
>