as they can, while if you append a @samp{?} after them, it makes them
non-greedy: they will match as little as possible.
-@item \@{n,m\@}
+@item \@{@var{n},@var{m}\@}
is another postfix operator that specifies an interval of iteration:
-the preceding regular expression must match between @samp{n} and
-@samp{m} times. If @samp{m} is omitted, then there is no upper bound
-and if @samp{,m} is omitted, then the regular expression must match
-exactly @samp{n} times. @*
+the preceding regular expression must match between @var{n} and
+@var{m} times. If @var{m} is omitted, then there is no upper bound
+and if @var{,m} is omitted, then the regular expression must match
+exactly @var{n} times. @*
@samp{\@{0,1\@}} is equivalent to @samp{?}. @*
@samp{\@{0,\@}} is equivalent to @samp{*}. @*
@samp{\@{1,\@}} is equivalent to @samp{+}. @*
-@samp{\@{n\@}} is equivalent to @samp{\@{n,n\@}}.
+@samp{\@{@var{n}\@}} is equivalent to @samp{\@{@var{n},@var{n}\@}}.
@item [ @dots{} ]
is a @dfn{character set}, which begins with @samp{[} and is terminated
This last application is not a consequence of the idea of a
parenthetical grouping; it is a separate feature that is assigned as a
second meaning to the same @samp{\( @dots{} \)} construct. In practice
-there is no conflict between the two meanings.
+there is almost no conflict between the two meanings.
+
+@item \(?: @dots{} \)
+is another grouping construct (often called ``shy'') that serves the same
+first two purposes, but not the third:
+it cannot be referred to later on by number. This is only useful
+for mechanically constructed regular expressions where grouping
+constructs need to be introduced implicitly and hence risk changing the
+numbering of subsequent groups.
@item \@var{d}
matches the same text that matched the @var{d}th occurrence of a
+2000-03-08 Stefan Monnier <monnier@cs.yale.edu>
+
+ This is a big redesign of failure-stack and register handling, prompted
+ by bugs revealed when trying to add shy-groups. Overall, what happened
+ is that loops are now structured a little differently, groups can be
+ shy and the code is a little simpler.
+
+ * regex.h: Update the copyright.
+ (RE_SHY_GROUPS): New value.
+ (RE_UNMATCHED_RIGHT_PAREN_ORD): Renumber.
+ (RE_SYNTAX_EMACS): Add RE_SHY_GROUPS.
+
+ * regex.c (enum re_opcode_t): Remove jump_past_alt, maybe_pop_jump,
+ push_dummy_failure and dumy_failure_jump.
+ Add on_failure_jump_(exclusive, loop and smart).
+ Also fix the comment for (start|stop)_memory since they now only take
+ one argument (the second has becomes unnecessary).
+ (print_partial_compiled_pattern): Adjust for changes in re_opcode_t.
+ (print_compiled_pattern): Use %ld to printf long ints and flush to make
+ debugging a little easier.
+ (union fail_stack_elt): Make the integer unsigned.
+ (struct fail_stack_type): Add a `frame' element.
+ (INIT_FAIL_STACK): Init `frame' as well.
+ (POP_PATTERN_OP): New macro for re_compile_fastmap.
+ (DEBUG_PUSH, DEBUG_POP): Remove.
+ (NUM_REG_ITEMS): Remove.
+ (NUM_NONREG_ITEMS): Adjust.
+ (FAILURE_PAT, FAILURE_STR, NEXT_FAILURE_HANDLE, TOP_FAILURE_HANDLE):
+ New macros for the cycle detection.
+ (ENSURE_FAIL_STACK): New macro for PUSH_FAILURE_(REG|POINT).
+ (PUSH_FAILURE_REG, POP_FAILURE_REG, CHECK_INFINITE_LOOP): New macros.
+ (PUSH_FAILURE_POINT): Don't push registers any more.
+ The pattern address pushed is not the destination of the jump
+ but the source of it instead.
+ (NUM_FAILURE_ITEMS): Remove.
+ (POP_FAILURE_POINT): Adapt to the new stack structure (i.e. pop
+ registers before the actual failure point).
+ Don't hardcode any meaning for str==NULL anymore.
+ (union register_info_type, REG_MATCH_NULL_STRING_P, IS_ACTIVE)
+ (MATCHED_SOMETHING, EVER_MATCHED_SOMETHING, SET_REGS_MATCHED): Remove.
+ (REG_UNSET_VALUE): Use NULL (why not?).
+ (compile_range): Remove declaration since it doesn't exist.
+ (struct compile_stack_elt_t): Remove inner_group_offset.
+ (old_reg(start|end), reg_info, reg_dummy, reg_info_dummy): Remove.
+ (regex_grow_registers): Remove dead code.
+ (FIXUP_ALT_JUMP): New macro.
+ (regex_compile): Add shy-groups
+ Change loops to use on_failure_jump_smart&jump instead of
+ on_failure_jump&maybe_pop_jump.
+ Change + loops to eliminate the initial (dummy_failure_)jump.
+ Remove c1_base (looks like unused variable to me).
+ Use `jump' instead of `jump_past_alt' and don't bother with
+ push_dummy_failure in alternatives since it is now unnecessary.
+ Use FIXUP_ALT_JUMP.
+ Eliminate a useless `#ifdef emacs' for (re)allocating the stack.
+ (re_compile_fastmap): Remove dead variables i and num_regs.
+ Exit from loop when bufp->can_be_null rather than jumping to `done'.
+ Avoid jumping backwards so as to ensure termination.
+ Use PATTERN_STACK_EMPTY and POP_PATTERN_OP.
+ Improved handling of backreferences.
+ Remove dead code in handling of `anychar'.
+ (skip_noops, mutually_exclusive_p): New functions taken from the
+ handling of `maybe_pop_jump' in re_match_2_internal.
+ Slightly improve mutually_exclusive_p to handle ".+\n".
+ ((lowest|highest)_active_reg, NO_(LOWEST|HIGHEST)_ACTIVE_REG)
+ Remove.
+ (re_match_2_internal): Use %p instead of 0x%x when printf'ing ptrs.
+ Don't SET_REGS_MATCHED anymore. Remove many dead variables.
+ Push register (in `start_memory') on the stack rather than storing it
+ in old_reg(start|end).
+ Remove the cycle detection from `stop_memory', replaced by the use
+ of on_failure_jump_loop for greedy loops.
+ Add code for the new on_failure_jump_<foo>.
+ Remove ad-hoc code in `on_failure_jump' to push more registers
+ in the case of a loop.
+ Take out code from `maybe_pop_jump' into separate functions and
+ adapt it to the semantics of `on_failure_jump_smart'.
+ Remove jump_past_alt, dummy_failure_jump and push_dummy_failure.
+ Remove dummy_failure handling and handling of `failures to jump
+ to on_failure_jump' (this last one was already dead code, it seems).
+ ((group|alt|common_op)_match_null_string_p): Remove.
+
2000-03-08 Dave Love <fx@gnu.org>
* config.in: Don't depend on __STDC__ for volatile.
projects / emacs.git / commitdiff