Loop Keywords (ANSI and GNU Common Lisp Document)

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#### 6.1.1.4 Loop Keywords

Loop keywords are not true keywords_1; they are special symbols, recognized by name rather than object identity, that are meaningful only to the loop facility. A loop keyword is a symbol but is recognized by its name (not its identity), regardless of the packages in which it is accessible.

In general, loop keywords are not external symbols of the `COMMON-LISP` package, except in the coincidental situation that a symbol with the same name as a loop keyword was needed for some other purpose in Common Lisp. For example, there is a symbol in the `COMMON-LISP` package whose name is `"UNLESS"` but not one whose name is `"UNTIL"`.

If no loop keywords are supplied in a loop form, the Loop Facility executes the loop body repeatedly; see Simple Loop.