6.26.2 Standard Forth locals ¶

The Forth-2012 standard defines a syntax for locals that is a restricted version of Gforth’s locals:

• Locals can only be cell-sized values (no type specifiers are allowed).
• Locals can be defined only outside control structures.
• Only one locals definition is allowed per colon definition.
• Locals can interfere with explicit usage of the return stack. For the exact (and long) rules, see the standard. If you don’t use return stack accessing words in a definition using locals, you will be all right. The purpose of this rule is to make locals implementation on the return stack easier.
• The whole locals definition must be in one line.

The Standard Forth locals wordset itself consists of two words: {: and:

(local) ( addr u –  ) local “paren-local-paren”

The Forth-2012 locals extension wordset also defines a syntax using locals|, but it is so awful that we strongly recommend not to use it, and the standardization committee standardized another, better syntax (the one using {:). We have implemented this syntax only to make porting to Gforth easy. The problem with this syntax is that the locals are defined in an order reversed with respect to the standard stack comment notation, making programs harder to read, and easier to misread and miswrite.