Mercurial > hg > octave-lojdl
changeset 2765:c44d1e4cd35b
[project @ 1997-03-01 02:53:03 by jwe]
author | jwe |
---|---|
date | Sat, 01 Mar 1997 02:53:03 +0000 |
parents | 2c0f259cf83d |
children | 62dc317d97b9 |
files | doc/interpreter/grammar.texi doc/interpreter/octave.texi doc/interpreter/stmt.texi |
diffstat | 3 files changed, 112 insertions(+), 11 deletions(-) [+] |
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--- a/doc/interpreter/grammar.texi +++ b/doc/interpreter/grammar.texi @@ -25,16 +25,18 @@ @group all_va_args endwhile break for -catch function -continue global -else gplot -elseif gsplot -end if +case function +catch global +continue gplot +else gsplot +elseif if +end otherwise end_try_catch return -end_unwind_protect try -endfor unwind_protect -endfunction unwind_protect_cleanup -endif while +end_unwind_protect switch +endfor try +endfunction unwind_protect +endif unwind_protect_cleanup +endswitch while @end group @end example
--- a/doc/interpreter/octave.texi +++ b/doc/interpreter/octave.texi @@ -260,6 +260,7 @@ Statements * The if Statement:: +* The switch Statement:: * The while Statement:: * The for Statement:: * The break Statement::
--- a/doc/interpreter/stmt.texi +++ b/doc/interpreter/stmt.texi @@ -33,6 +33,7 @@ @menu * The if Statement:: +* The switch Statement:: * The while Statement:: * The for Statement:: * The break Statement:: @@ -42,7 +43,7 @@ * Continuation Lines:: @end menu -@node The if Statement, The while Statement, Statements, Statements +@node The if Statement, The switch Statement, Statements, Statements @section The @code{if} Statement @cindex @code{if} statement @cindex @code{else} statement @@ -253,7 +254,104 @@ The default value of @code{warn_assign_as_truth_value} is 1. @end defvr -@node The while Statement, The for Statement, The if Statement, Statements +@node The switch Statement, The while Statement, The if Statement, Statements +@section The @code{switch} Statement +@cindex @code{switch} statement +@cindex @code{case} statement +@cindex @code{otherwise} statement +@cindex @code{endswitch} statement + +The @code{switch} statement was introduced in Octave 2.0.5. It should +be considered experimental, and details of the implementation may change +slightly in future versions of Octave. If you have comments or would +like to share your experiences in trying to use this new command in real +programs, please send them to +@email{octave-maintainers@@bevo.che.wisc.edu}. (But if you think you've +found a bug, please report it to @email{bug-octave@@bevo.che.wisc.edu}. + +The general form of the @code{switch} statement is + +@example +@group +switch @var{expression} + case @var{label} + @var{command_list} + case @var{label} + @var{command_list} + @dots{} + + otherwise + @var{command_list} +endswitch +@end group +@end example + +@itemize @bullet +@item +The identifiers @code{switch}, @code{case}, @code{otherwise}, and +@code{endswitch} are now keywords. + +@item +The @var{label} may be any expression. + +@item +Duplicate @var{label} values are not detected. The @var{command_list} +corresponding to the first match will be executed. + +@item +You must have at least one @code{case @var{label} @var{command_list}} +clause. + +@item +The @code{otherwise @var{command_list}} clause is optional. + +@item +As with all other specific @code{end} keywords, @code{endswitch} may be +replaced by @code{end}, but you can get better diagnostics if you use +the specific forms. + +@item +Cases are exclusive, so they don't `fall through' as do the cases +in the switch statement of the C language. + +@item +The @var{command_list} elements are not optional. Making the list +optional would have meant requiring a separator between the label and +the command list. Otherwise, things like + +@example +@group +switch (foo) + case (1) -2 + @dots{} +@end group +@end example + +@noindent +would produce surprising results, as would + +@example +@group +switch (foo) + case (1) + case (2) + doit (); + @dots{} +@end group +@end example + +@noindent +particularly for C programmers. + +@item +The implementation is simple-minded and currently offers no real +performance improvement over an equivalent @code{if} block, even if all +the labels are integer constants. Perhaps a future variation on this +could detect all constant integer labels and improve performance by +using a jump table. +@end itemize + +@node The while Statement, The for Statement, The switch Statement, Statements @section The @code{while} Statement @cindex @code{while} statement @cindex @code{endwhile} statement