Xcas operators

### 4.14.2 Xcas operators

- $ is the infixed version of seq, for example :
  (2`^`k)$(k=0..3)= seq(2`^`k,k=0..3)=(1,2,4,8) (do not forget to put parenthesis around the arguments),
- mod or % to define a modular number,
- @ to compose functions for example : (f@g)(x)=f(g(x)),
- @@ to compose a function many times (like a power, replacing multiplication by composition), for example : (f@@3)(x)=f(f(f(x))),
- minus union intersect to get the difference, the union and the intersection of two sets,
- -> to define a function,
- := => to store an expression in a variable (it is the infixed version of sto and the argument order is permuted for :=), for example : a:=2 or 2=>a or sto(2,a).
- =< to store an expression in a variable, but the storage is done by reference if the target is a matrix element or a list element. This is faster if you modify objects inside an existing list or matrix of large size, because no copy is made, the change is done in place. Use with care, all objects pointing to this matrix or list will be modified.