6.22.2 Standard Forth locals ¶

The Forth-2012 standard defines a syntax for locals is 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 per definition is allowed.
• 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 ANS Forth locals extension wordset defines a syntax using locals|, but it is so awful that we strongly recommend not to use it. We have implemented this syntax to make porting to Gforth easy, but do not document it here. 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. The only merit of this syntax is that it is easy to implement using the ANS Forth locals wordset, but then, so is the {: syntax.