This keyword defines a function. The syntax of the expression is the same as for a .param (2.8.5).

General form:

.func <ident> { <expr> }
.func <ident> = { <expr> }

Examples:

.func icos(x) {cos(x) - 1}
.func f(x,y) {x*y}
.func foo(a,b) = {a + b}

.func will initiate a replacement operation. After reading the input files, and before parameters are evaluated, all occurrences of the icos(x) function will be replaced by cos(x)-1. All occurrences of f(x,y) will be replaced by x*y. Function statements may be nested to a depth of t.b.d..