apply

The procedure apply allows you to call any procedure, and specify a list of values to be passed as arguments. apply takes a procedure and a list of values, and then calls the procedure with those values as arguments.

For example, (apply + '(1 2)) passes the values 1 and 2 to +, and is equivalent to (+ 1 2).

You'll seldom need to use apply, because normal procedure calling works fine in most situations. Occasionally, though, it is convenient to be able to apply a procedure to a list of values that have already been computed. (I'll show an example in [ chapter 4? ].)