3.1.7 Return Values

Ordinarily the result of calling a function is a single object. Sometimes, however, it is convenient for a function to compute several objects and return them.

In order to receive other than exactly one value from a form, one of several special forms or macros must be used to request those values. If a form produces multiple values which were not requested in this way, then the first value is given to the caller and all others are discarded; if the form produces zero values, then the caller receives nil as a value.

The next figure lists some operators for receiving multiple values[2]. These operators can be used to specify one or more forms to evaluate and where to put the values returned by those forms.

multiple-value-bind  multiple-value-prog1  return-from  
multiple-value-call  multiple-value-setq   throw        
multiple-value-list  return                             

Figure 3-5. Some operators applicable to receiving multiple values

The function values can produce multiple values[2]. (values) returns zero values; (values form) returns the primary value returned by form; (values form1 form2) returns two values, the primary value of form1 and the primary value of form2; and so on.

See multiple-values-limit and values-list.