fastfib(0,1,0).
fastfib(1,0,1).
fastfib(2,1,1).
fastfib(A,B,C):-
  A > 2,
  (divmod(A,2,X,1),fastfib(X,E,F),FF is F*F,B is 2*E*F+FF,C is E*E+FF+B;
   divmod(A,2,X,0),fastfib(X,E,F),FF is F*F,B is E*E+FF, C is 2*E*F+FF).
fib(A,C):- fastfib(A,B,C).

x  <int> <int>            Bitwise XOR. A ^ B in Python.
x  <lst> <any>            First occurrence. Return the index of the first element of A equal to B, or -1 if none exists.
x  <str> <str>            First occurrence. Return the index of the first substring of A equal to B, or -1 if none exists.
x  <non-lst> <lst>        All occurrences. Returns a list of the indexes of elements of B that equal A.
x  <str> <non-lst>        First occurence. Return the index of the first substring of A equal to str(B), or -1 if none exists.

.u <l:NY> <seq/num> <any> Cumulative reduce. Reduce B from left to right, with function A(_, _) and C as starting value, and return all intermediate values, starting with C. A takes current value, next element of B as inputs.
.u <l:NY> <any> <none>    Cumulative fixed-point. Apply A(_, _) until a result that has occurred before is found. Starting value B. Return all intermediate results, starting with B. A takes current value, iteration number as inputs.

Types:
num = int, float
cmp = complex
seq = str, list, tuple
lst = list, tuple
idx = str, list, dict
col = str, list, set, dict
any = any expression (a for short)
blk = a code block (any series of statements)
... = any number of arguments of any type.
n:_ = n _ arguments.
var = variable. Not evaluated.
func = function. Not evaluated.
func n = function with arity n.
pfn = Preceding function of arity n. *F, for instance.
l:_ = Lambda with lambda variable(s) _
pos = positive int.
nneg = nonnegative int.

?  <any> <any> <any>      Ternary. A ? B : C in C-like languages. B if A else C in Python.

if(/}/.test(this.firstChar())) {