The applyop command manipulates the selected parts of an expression. The first argument, f, is applied to the operands of e specified by i.

If i is an integer, applyop( f, i, e) applies f to the ith operand of e. This is equivalent to subsop( i = f(op( i, e)), e). For example, if the value of e is the sum , applyop( f, 2, e) computes .

If i is a list of integers, the call applyop( f, i, e) is equivalent to subsop( i = f(op( i, e)), e). This allows you to manipulate any suboperand of an expression.

If i is a set, f is applied simultaneously to all operands of e specified in the set. Note: applyop( f, {}, e) returns e.

Any additional arguments xk are passed as additional arguments to f in the order given.