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The following syntax description provides an overview of the syntax for loop clauses.16
A loop consists of the following types of clauses:
initial-final ::= initially | finally variables ::= with | initial-final | for-as | repeat main ::= unconditional | accumulation | conditional | termination | initial-final loop ::= (loop [named name] {variables}* {main}*)
Note that a loop must have at least one clause; however, for backward compatibility, the following format is also supported:
(loop {tag | expr}*)
where ‘expr’ is any Common Lisp expression that can be evaluated, and ‘tag’ is any symbol not identifiable as a loop keyword. Such a format is roughly equivalent to the following one:
(loop do {tag | expr}*)
A loop prologue consists of any automatic variable initializations prescribed
by the variable clauses, along with any initially
clauses in the order they
appear in the source.
A loop epilogue consists of finally
clauses, if any, along with any
implicit return value from an accumulation clause or an end-test clause.
Detailed syntax descriptions of individual clauses appear in sections 26.6 through 26.12.