Block Closure

[David Collier-Brown]

In article <757 at l.cc.purdue.edu> cik at l.cc.purdue.edu (Herman Rubin) writes:
>I find both of these methods at times easy to follow, and at times hard to
>follow.  There is also the problem of a multiple break.
>[...]
>	break LABEL
>	endall LABEL

 Well, both have been tried, with mixed results.  One could label
begin-end blocks in PL/1, and add either the block label of the name
of the control structure between the "end" and its ";".  At least
two compilers used this to double-check block nesting and produce
warning messages.
  Similarly, some PL/1 variants (and my memory is fuzzy here...)
allowed a leave <label> statement which exited a named block. This
may have been part of the ANSI standard, but that was too long ago.

 Labelled blocks and "endall" existed in BCPL, but were very
little-used. It was not obvious whether it was because it was
non-traditional or buggy, but is usually remembered in terms of the
claim that it lead to making block-balancing errors.
-- 
 David Collier-Brown.                 {mnetor yunexus utgpu}!geac!daveb
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