Function set

set of elementary functions, appropriate to the problem, that are available as inner nodes in a GP representation. Together with the terminal set they are used to build a tree-shaped individual. Examples of function set members are arithmetic operators and mathematical functions $\{$+, $-$, $*$, /, sin, cos$\}$ for symbolic regression and elements of a programming language $\{$if-then-else, for, do-until, $\ldots \}$ for building programs.