5.9.7 Quotations

A quotation is an anonymous colon definition inside another colon definition. Quotations are useful when dealing with words that consume an execution token, like catch or outfile-execute. E.g. consider the following example of using outfile-execute (see Redirection):

: some-warning ( n -- )
    cr ." warning# " . ;

: print-some-warning ( n -- )
    ['] some-warning stderr outfile-execute ;

Here we defined some-warning as a helper word whose xt we could pass to outfile-execute. Instead, we can use a quotation to define such a word anonymously inside print-some-warning:

: print-some-warning ( n -- )
  [: cr ." warning# " . ;] stderr outfile-execute ;

The quotation is bouded by [: and ;]. It produces an execution token at run-time.

[:       compile-time: – quotation-sys flag colon-sys         gforth       “bracket-colon”

Starts a quotation

;]       compile-time: quotation-sys – ; run-time: – xt         gforth       “semi-bracket”

ends a quotation