Issue: TAGBODY-CONTENTS (version 1)

[vanroggen%aitg.DEC@decwrl.dec.com]

Issue:		TAGBODY-CONTENTS
References:	TAGBODY (pp 130-131 of CLtL)
Category:	CLARIFICATION
Edit History:	13-Sept-88, version 1 by Walter van Roggen

Problem Description:

  CLtL isn't clear on what may be in the body of a TAGBODY.

Proposal: (TAGBODY-CONTENTS:RESTRICT)

  Anything in a TAGBODY other than a tag (a symbol or an integer) or
  a list is an error.

  It is an error for the same (EQL) tag to appear more than once in the
  body of a TAGBODY.  (However, a TAGBODY may have the same tag as
  another TAGBODY in which it nests, in which case the tag in the outer
  TAGBODY is shadowed, as already specified.)

  The same restrictions apply to all forms which implicitly use TAGBODY,
  such as PROG and DO.

Current Practice:

Cost to Implementors:

  A few simple checks are probably all that's needed, and probably
  most implementations (both interpreters and compilers) already perform them.

Cost to Users:

  Unlikely to affect any portable code.  If there are implementations which
  support other objects as tags (floats, for example), there may be simple
  editing necessary.

Benefits:

  A slightly more precise description of the language.

Discussion:

  This first appeared in ">GLS>clarifications.text" of 12/06/85.