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363 lines
14 KiB
363 lines
14 KiB
# -*- Autoconf -*-
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# This file is part of Autoconf.
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# foreach-based replacements for recursive functions.
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# Speeds up GNU M4 1.4.x by avoiding quadratic $@ recursion, but penalizes
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# GNU M4 1.6 by requiring more memory and macro expansions.
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#
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# Copyright (C) 2008-2017 Free Software Foundation, Inc.
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# This file is part of Autoconf. This program is free
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# software; you can redistribute it and/or modify it under the
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# terms of the GNU General Public License as published by the
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# Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# Under Section 7 of GPL version 3, you are granted additional
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# permissions described in the Autoconf Configure Script Exception,
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# version 3.0, as published by the Free Software Foundation.
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#
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# You should have received a copy of the GNU General Public License
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# and a copy of the Autoconf Configure Script Exception along with
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# this program; see the files COPYINGv3 and COPYING.EXCEPTION
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# respectively. If not, see <https://www.gnu.org/licenses/>.
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# Written by Eric Blake.
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# In M4 1.4.x, every byte of $@ is rescanned. This means that an
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# algorithm on n arguments that recurses with one less argument each
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# iteration will scan n * (n + 1) / 2 arguments, for O(n^2) time. In
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# M4 1.6, this was fixed so that $@ is only scanned once, then
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# back-references are made to information stored about the scan.
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# Thus, n iterations need only scan n arguments, for O(n) time.
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# Additionally, in M4 1.4.x, recursive algorithms did not clean up
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# memory very well, requiring O(n^2) memory rather than O(n) for n
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# iterations.
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#
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# This file is designed to overcome the quadratic nature of $@
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# recursion by writing a variant of m4_foreach that uses m4_for rather
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# than $@ recursion to operate on the list. This involves more macro
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# expansions, but avoids the need to rescan a quadratic number of
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# arguments, making these replacements very attractive for M4 1.4.x.
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# On the other hand, in any version of M4, expanding additional macros
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# costs additional time; therefore, in M4 1.6, where $@ recursion uses
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# fewer macros, these replacements actually pessimize performance.
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# Additionally, the use of $10 to mean the tenth argument violates
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# POSIX; although all versions of m4 1.4.x support this meaning, a
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# future m4 version may switch to take it as the first argument
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# concatenated with a literal 0, so the implementations in this file
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# are not future-proof. Thus, this file is conditionally included as
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# part of m4_init(), only when it is detected that M4 probably has
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# quadratic behavior (ie. it lacks the macro __m4_version__).
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#
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# Please keep this file in sync with m4sugar.m4.
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# _m4_foreach(PRE, POST, IGNORED, ARG...)
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# ---------------------------------------
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# Form the common basis of the m4_foreach and m4_map macros. For each
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# ARG, expand PRE[ARG]POST[]. The IGNORED argument makes recursion
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# easier, and must be supplied rather than implicit.
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#
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# This version minimizes the number of times that $@ is evaluated by
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# using m4_for to generate a boilerplate into _m4_f then passing $@ to
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# that temporary macro. Thus, the recursion is done in m4_for without
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# reparsing any user input, and is not quadratic. For an idea of how
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# this works, note that m4_foreach(i,[1,2],[i]) calls
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# _m4_foreach([m4_define([i],],[)i],[],[1],[2])
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# which defines _m4_f:
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# $1[$4]$2[]$1[$5]$2[]_m4_popdef([_m4_f])
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# then calls _m4_f([m4_define([i],],[)i],[],[1],[2]) for a net result:
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# m4_define([i],[1])i[]m4_define([i],[2])i[]_m4_popdef([_m4_f]).
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m4_define([_m4_foreach],
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[m4_if([$#], [3], [],
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[m4_pushdef([_m4_f], _m4_for([4], [$#], [1],
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[$0_([1], [2],], [)])[_m4_popdef([_m4_f])])_m4_f($@)])])
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m4_define([_m4_foreach_],
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[[$$1[$$3]$$2[]]])
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# m4_case(SWITCH, VAL1, IF-VAL1, VAL2, IF-VAL2, ..., DEFAULT)
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# -----------------------------------------------------------
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# Find the first VAL that SWITCH matches, and expand the corresponding
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# IF-VAL. If there are no matches, expand DEFAULT.
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#
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# Use m4_for to create a temporary macro in terms of a boilerplate
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# m4_if with final cleanup. If $# is even, we have DEFAULT; if it is
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# odd, then rounding the last $# up in the temporary macro is
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# harmless. For example, both m4_case(1,2,3,4,5) and
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# m4_case(1,2,3,4,5,6) result in the intermediate _m4_case being
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# m4_if([$1],[$2],[$3],[$1],[$4],[$5],_m4_popdef([_m4_case])[$6])
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m4_define([m4_case],
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[m4_if(m4_eval([$# <= 2]), [1], [$2],
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[m4_pushdef([_$0], [m4_if(]_m4_for([2], m4_eval([($# - 1) / 2 * 2]), [2],
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[_$0_(], [)])[_m4_popdef(
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[_$0])]m4_dquote($m4_eval([($# + 1) & ~1]))[)])_$0($@)])])
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m4_define([_m4_case_],
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[$0_([1], [$1], m4_incr([$1]))])
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m4_define([_m4_case__],
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[[[$$1],[$$2],[$$3],]])
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# m4_bmatch(SWITCH, RE1, VAL1, RE2, VAL2, ..., DEFAULT)
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# -----------------------------------------------------
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# m4 equivalent of
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#
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# if (SWITCH =~ RE1)
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# VAL1;
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# elif (SWITCH =~ RE2)
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# VAL2;
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# elif ...
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# ...
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# else
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# DEFAULT
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#
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# We build the temporary macro _m4_b:
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# m4_define([_m4_b], _m4_defn([_m4_bmatch]))_m4_b([$1], [$2], [$3])...
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# _m4_b([$1], [$m-1], [$m])_m4_b([], [], [$m+1]_m4_popdef([_m4_b]))
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# then invoke m4_unquote(_m4_b($@)), for concatenation with later text.
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m4_define([m4_bmatch],
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[m4_if([$#], 0, [m4_fatal([$0: too few arguments: $#])],
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[$#], 1, [m4_fatal([$0: too few arguments: $#: $1])],
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[$#], 2, [$2],
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[m4_pushdef([_m4_b], [m4_define([_m4_b],
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_m4_defn([_$0]))]_m4_for([3], m4_eval([($# + 1) / 2 * 2 - 1]),
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[2], [_$0_(], [)])[_m4_b([], [],]m4_dquote([$]m4_eval(
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[($# + 1) / 2 * 2]))[_m4_popdef([_m4_b]))])m4_unquote(_m4_b($@))])])
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m4_define([_m4_bmatch],
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[m4_if(m4_bregexp([$1], [$2]), [-1], [], [[$3]m4_define([$0])])])
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m4_define([_m4_bmatch_],
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[$0_([1], m4_decr([$1]), [$1])])
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m4_define([_m4_bmatch__],
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[[_m4_b([$$1], [$$2], [$$3])]])
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# m4_cond(TEST1, VAL1, IF-VAL1, TEST2, VAL2, IF-VAL2, ..., [DEFAULT])
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# -------------------------------------------------------------------
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# Similar to m4_if, except that each TEST is expanded when encountered.
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# If the expansion of TESTn matches the string VALn, the result is IF-VALn.
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# The result is DEFAULT if no tests passed. This macro allows
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# short-circuiting of expensive tests, where it pays to arrange quick
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# filter tests to run first.
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#
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# m4_cond already guarantees either 3*n or 3*n + 1 arguments, 1 <= n.
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# We only have to speed up _m4_cond, by building the temporary _m4_c:
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# m4_define([_m4_c], _m4_defn([m4_unquote]))_m4_c([m4_if(($1), [($2)],
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# [[$3]m4_define([_m4_c])])])_m4_c([m4_if(($4), [($5)],
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# [[$6]m4_define([_m4_c])])])..._m4_c([m4_if(($m-2), [($m-1)],
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# [[$m]m4_define([_m4_c])])])_m4_c([[$m+1]]_m4_popdef([_m4_c]))
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# We invoke m4_unquote(_m4_c($@)), for concatenation with later text.
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m4_define([_m4_cond],
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[m4_pushdef([_m4_c], [m4_define([_m4_c],
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_m4_defn([m4_unquote]))]_m4_for([2], m4_eval([$# / 3 * 3 - 1]), [3],
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[$0_(], [)])[_m4_c(]m4_dquote(m4_dquote(
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[$]m4_eval([$# / 3 * 3 + 1])))[_m4_popdef([_m4_c]))])m4_unquote(_m4_c($@))])
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m4_define([_m4_cond_],
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[$0_(m4_decr([$1]), [$1], m4_incr([$1]))])
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m4_define([_m4_cond__],
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[[_m4_c([m4_if(($$1), [($$2)], [[$$3]m4_define([_m4_c])])])]])
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# m4_bpatsubsts(STRING, RE1, SUBST1, RE2, SUBST2, ...)
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# ----------------------------------------------------
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# m4 equivalent of
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#
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# $_ = STRING;
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# s/RE1/SUBST1/g;
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# s/RE2/SUBST2/g;
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# ...
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#
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# m4_bpatsubsts already validated an odd number of arguments; we only
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# need to speed up _m4_bpatsubsts. To avoid nesting, we build the
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# temporary _m4_p:
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# m4_define([_m4_p], [$1])m4_define([_m4_p],
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# m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$2], [$3]))m4_define([_m4_p],
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# m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$4], [$5]))m4_define([_m4_p],...
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# m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$m-1], [$m]))m4_unquote(
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# _m4_defn([_m4_p])_m4_popdef([_m4_p]))
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m4_define([_m4_bpatsubsts],
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[m4_pushdef([_m4_p], [m4_define([_m4_p],
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]m4_dquote([$]1)[)]_m4_for([3], [$#], [2], [$0_(],
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[)])[m4_unquote(_m4_defn([_m4_p])_m4_popdef([_m4_p]))])_m4_p($@)])
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m4_define([_m4_bpatsubsts_],
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[$0_(m4_decr([$1]), [$1])])
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m4_define([_m4_bpatsubsts__],
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[[m4_define([_m4_p],
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m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$$1], [$$2]))]])
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# m4_shiftn(N, ...)
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# -----------------
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# Returns ... shifted N times. Useful for recursive "varargs" constructs.
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#
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# m4_shiftn already validated arguments; we only need to speed up
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# _m4_shiftn. If N is 3, then we build the temporary _m4_s, defined as
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# ,[$5],[$6],...,[$m]_m4_popdef([_m4_s])
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# before calling m4_shift(_m4_s($@)).
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m4_define([_m4_shiftn],
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[m4_if(m4_incr([$1]), [$#], [], [m4_pushdef([_m4_s],
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_m4_for(m4_eval([$1 + 2]), [$#], [1],
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[[,]m4_dquote($], [)])[_m4_popdef([_m4_s])])m4_shift(_m4_s($@))])])
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# m4_do(STRING, ...)
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# ------------------
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# This macro invokes all its arguments (in sequence, of course). It is
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# useful for making your macros more structured and readable by dropping
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# unnecessary dnl's and have the macros indented properly.
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#
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# Here, we use the temporary macro _m4_do, defined as
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# $1[]$2[]...[]$n[]_m4_popdef([_m4_do])
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m4_define([m4_do],
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[m4_if([$#], [0], [],
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[m4_pushdef([_$0], _m4_for([1], [$#], [1],
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[$], [[[]]])[_m4_popdef([_$0])])_$0($@)])])
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# m4_dquote_elt(ARGS)
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# -------------------
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# Return ARGS as an unquoted list of double-quoted arguments.
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#
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# _m4_foreach to the rescue.
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m4_define([m4_dquote_elt],
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[m4_if([$#], [0], [], [[[$1]]_m4_foreach([,m4_dquote(], [)], $@)])])
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# m4_reverse(ARGS)
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# ----------------
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# Output ARGS in reverse order.
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#
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# Invoke _m4_r($@) with the temporary _m4_r built as
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# [$m], [$m-1], ..., [$2], [$1]_m4_popdef([_m4_r])
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m4_define([m4_reverse],
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[m4_if([$#], [0], [], [$#], [1], [[$1]],
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[m4_pushdef([_m4_r], [[$$#]]_m4_for(m4_decr([$#]), [1], [-1],
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[[, ]m4_dquote($], [)])[_m4_popdef([_m4_r])])_m4_r($@)])])
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# m4_map_args_pair(EXPRESSION, [END-EXPR = EXPRESSION], ARG...)
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# -------------------------------------------------------------
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# Perform a pairwise grouping of consecutive ARGs, by expanding
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# EXPRESSION([ARG1], [ARG2]). If there are an odd number of ARGs, the
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# final argument is expanded with END-EXPR([ARGn]).
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#
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# Build the temporary macro _m4_map_args_pair, with the $2([$m+1])
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# only output if $# is odd:
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# $1([$3], [$4])[]$1([$5], [$6])[]...$1([$m-1],
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# [$m])[]m4_default([$2], [$1])([$m+1])[]_m4_popdef([_m4_map_args_pair])
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m4_define([m4_map_args_pair],
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[m4_if([$#], [0], [m4_fatal([$0: too few arguments: $#])],
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[$#], [1], [m4_fatal([$0: too few arguments: $#: $1])],
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[$#], [2], [],
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[$#], [3], [m4_default([$2], [$1])([$3])[]],
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[m4_pushdef([_$0], _m4_for([3],
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m4_eval([$# / 2 * 2 - 1]), [2], [_$0_(], [)])_$0_end(
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[1], [2], [$#])[_m4_popdef([_$0])])_$0($@)])])
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m4_define([_m4_map_args_pair_],
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[$0_([1], [$1], m4_incr([$1]))])
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m4_define([_m4_map_args_pair__],
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[[$$1([$$2], [$$3])[]]])
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m4_define([_m4_map_args_pair_end],
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[m4_if(m4_eval([$3 & 1]), [1], [[m4_default([$$2], [$$1])([$$3])[]]])])
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# m4_join(SEP, ARG1, ARG2...)
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# ---------------------------
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# Produce ARG1SEPARG2...SEPARGn. Avoid back-to-back SEP when a given ARG
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# is the empty string. No expansion is performed on SEP or ARGs.
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#
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# Use a self-modifying separator, since we don't know how many
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# arguments might be skipped before a separator is first printed, but
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# be careful if the separator contains $. _m4_foreach to the rescue.
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m4_define([m4_join],
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[m4_pushdef([_m4_sep], [m4_define([_m4_sep], _m4_defn([m4_echo]))])]dnl
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[_m4_foreach([_$0([$1],], [)], $@)_m4_popdef([_m4_sep])])
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m4_define([_m4_join],
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[m4_if([$2], [], [], [_m4_sep([$1])[$2]])])
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# m4_joinall(SEP, ARG1, ARG2...)
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# ------------------------------
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# Produce ARG1SEPARG2...SEPARGn. An empty ARG results in back-to-back SEP.
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# No expansion is performed on SEP or ARGs.
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#
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# A bit easier than m4_join. _m4_foreach to the rescue.
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m4_define([m4_joinall],
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[[$2]m4_if(m4_eval([$# <= 2]), [1], [],
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[_m4_foreach([$1], [], m4_shift($@))])])
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# m4_list_cmp(A, B)
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# -----------------
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# Compare the two lists of integer expressions A and B.
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#
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# m4_list_cmp takes care of any side effects; we only override
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# _m4_list_cmp_raw, where we can safely expand lists multiple times.
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# First, insert padding so that both lists are the same length; the
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# trailing +0 is necessary to handle a missing list. Next, create a
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# temporary macro to perform pairwise comparisons until an inequality
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# is found. For example, m4_list_cmp([1], [1,2]) creates _m4_cmp as
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# m4_if(m4_eval([($1) != ($3)]), [1], [m4_cmp([$1], [$3])],
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# m4_eval([($2) != ($4)]), [1], [m4_cmp([$2], [$4])],
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# [0]_m4_popdef([_m4_cmp]))
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# then calls _m4_cmp([1+0], [0*2], [1], [2+0])
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m4_define([_m4_list_cmp_raw],
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[m4_if([$1], [$2], 0,
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[_m4_list_cmp($1+0_m4_list_pad(m4_count($1), m4_count($2)),
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$2+0_m4_list_pad(m4_count($2), m4_count($1)))])])
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m4_define([_m4_list_pad],
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[m4_if(m4_eval($1 < $2), [1],
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[_m4_for(m4_incr([$1]), [$2], [1], [,0*])])])
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m4_define([_m4_list_cmp],
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[m4_pushdef([_m4_cmp], [m4_if(]_m4_for(
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[1], m4_eval([$# >> 1]), [1], [$0_(], [,]m4_eval([$# >> 1])[)])[
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[0]_m4_popdef([_m4_cmp]))])_m4_cmp($@)])
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m4_define([_m4_list_cmp_],
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[$0_([$1], m4_eval([$1 + $2]))])
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m4_define([_m4_list_cmp__],
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[[m4_eval([($$1) != ($$2)]), [1], [m4_cmp([$$1], [$$2])],
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]])
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# m4_max(EXPR, ...)
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# m4_min(EXPR, ...)
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# -----------------
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# Return the decimal value of the maximum (or minimum) in a series of
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# integer expressions.
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#
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# _m4_foreach to the rescue; we only need to replace _m4_minmax. Here,
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# we need a temporary macro to track the best answer so far, so that
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# the foreach expression is tractable.
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m4_define([_m4_minmax],
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[m4_pushdef([_m4_best], m4_eval([$2]))_m4_foreach(
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[m4_define([_m4_best], $1(_m4_best,], [))], m4_shift($@))]dnl
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[_m4_best[]_m4_popdef([_m4_best])])
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# m4_set_add_all(SET, VALUE...)
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# -----------------------------
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# Add each VALUE into SET. This is O(n) in the number of VALUEs, and
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# can be faster than calling m4_set_add for each VALUE.
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#
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# _m4_foreach to the rescue. If no deletions have occurred, then
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# avoid the speed penalty of m4_set_add.
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m4_define([m4_set_add_all],
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[m4_if([$#], [0], [], [$#], [1], [],
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[m4_define([_m4_set_size($1)], m4_eval(m4_set_size([$1])
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+ m4_len(_m4_foreach(m4_ifdef([_m4_set_cleanup($1)],
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[[m4_set_add]], [[_$0]])[([$1],], [)], $@))))])])
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m4_define([_m4_set_add_all],
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[m4_ifdef([_m4_set([$1],$2)], [],
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[m4_define([_m4_set([$1],$2)],
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[1])m4_pushdef([_m4_set([$1])], [$2])-])])
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