Number of arguments

This function may not behave as expected. Internally, all the expressions are implemented as combinations of elementary operations. Thus, the operation 'sum' has two arguments. For instance, summing a plus b has two arguments (a and b), but s i n left parenthesis x right parenthesis plus y asterisk times z has also two arguments: s i n left parenthesis x right parenthesis and y asterisk times z.

number_of_arguments(Expression)

Given an expression, returns its number of arguments.