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Editing: foreach.m4
# -*- Autoconf -*- # This file is part of Autoconf. # foreach-based replacements for recursive functions. # Speeds up GNU M4 1.4.x by avoiding quadratic $@ recursion, but penalizes # GNU M4 1.6 by requiring more memory and macro expansions. # # Copyright (C) 2008-2013 Free Software Foundation, Inc. # This file is part of Autoconf. This program is free # software; you can redistribute it and/or modify it under the # terms of the GNU General Public License as published by the # Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # Under Section 7 of GPL version 3, you are granted additional # permissions described in the Autoconf Configure Script Exception, # version 3.0, as published by the Free Software Foundation. # # You should have received a copy of the GNU General Public License # and a copy of the Autoconf Configure Script Exception along with # this program; see the files COPYINGv3 and COPYING.EXCEPTION # respectively. If not, see <http://www.gnu.org/licenses/>. # Written by Eric Blake. # In M4 1.4.x, every byte of $@ is rescanned. This means that an # algorithm on n arguments that recurses with one less argument each # iteration will scan n * (n + 1) / 2 arguments, for O(n^2) time. In # M4 1.6, this was fixed so that $@ is only scanned once, then # back-references are made to information stored about the scan. # Thus, n iterations need only scan n arguments, for O(n) time. # Additionally, in M4 1.4.x, recursive algorithms did not clean up # memory very well, requiring O(n^2) memory rather than O(n) for n # iterations. # # This file is designed to overcome the quadratic nature of $@ # recursion by writing a variant of m4_foreach that uses m4_for rather # than $@ recursion to operate on the list. This involves more macro # expansions, but avoids the need to rescan a quadratic number of # arguments, making these replacements very attractive for M4 1.4.x. # On the other hand, in any version of M4, expanding additional macros # costs additional time; therefore, in M4 1.6, where $@ recursion uses # fewer macros, these replacements actually pessimize performance. # Additionally, the use of $10 to mean the tenth argument violates # POSIX; although all versions of m4 1.4.x support this meaning, a # future m4 version may switch to take it as the first argument # concatenated with a literal 0, so the implementations in this file # are not future-proof. Thus, this file is conditionally included as # part of m4_init(), only when it is detected that M4 probably has # quadratic behavior (ie. it lacks the macro __m4_version__). # # Please keep this file in sync with m4sugar.m4. # _m4_foreach(PRE, POST, IGNORED, ARG...) # --------------------------------------- # Form the common basis of the m4_foreach and m4_map macros. For each # ARG, expand PRE[ARG]POST[]. The IGNORED argument makes recursion # easier, and must be supplied rather than implicit. # # This version minimizes the number of times that $@ is evaluated by # using m4_for to generate a boilerplate into _m4_f then passing $@ to # that temporary macro. Thus, the recursion is done in m4_for without # reparsing any user input, and is not quadratic. For an idea of how # this works, note that m4_foreach(i,[1,2],[i]) calls # _m4_foreach([m4_define([i],],[)i],[],[1],[2]) # which defines _m4_f: # $1[$4]$2[]$1[$5]$2[]_m4_popdef([_m4_f]) # then calls _m4_f([m4_define([i],],[)i],[],[1],[2]) for a net result: # m4_define([i],[1])i[]m4_define([i],[2])i[]_m4_popdef([_m4_f]). m4_define([_m4_foreach], [m4_if([$#], [3], [], [m4_pushdef([_m4_f], _m4_for([4], [$#], [1], [$0_([1], [2],], [)])[_m4_popdef([_m4_f])])_m4_f($@)])]) m4_define([_m4_foreach_], [[$$1[$$3]$$2[]]]) # m4_case(SWITCH, VAL1, IF-VAL1, VAL2, IF-VAL2, ..., DEFAULT) # ----------------------------------------------------------- # Find the first VAL that SWITCH matches, and expand the corresponding # IF-VAL. If there are no matches, expand DEFAULT. # # Use m4_for to create a temporary macro in terms of a boilerplate # m4_if with final cleanup. If $# is even, we have DEFAULT; if it is # odd, then rounding the last $# up in the temporary macro is # harmless. For example, both m4_case(1,2,3,4,5) and # m4_case(1,2,3,4,5,6) result in the intermediate _m4_case being # m4_if([$1],[$2],[$3],[$1],[$4],[$5],_m4_popdef([_m4_case])[$6]) m4_define([m4_case], [m4_if(m4_eval([$# <= 2]), [1], [$2], [m4_pushdef([_$0], [m4_if(]_m4_for([2], m4_eval([($# - 1) / 2 * 2]), [2], [_$0_(], [)])[_m4_popdef( [_$0])]m4_dquote($m4_eval([($# + 1) & ~1]))[)])_$0($@)])]) m4_define([_m4_case_], [$0_([1], [$1], m4_incr([$1]))]) m4_define([_m4_case__], [[[$$1],[$$2],[$$3],]]) # m4_bmatch(SWITCH, RE1, VAL1, RE2, VAL2, ..., DEFAULT) # ----------------------------------------------------- # m4 equivalent of # # if (SWITCH =~ RE1) # VAL1; # elif (SWITCH =~ RE2) # VAL2; # elif ... # ... # else # DEFAULT # # We build the temporary macro _m4_b: # m4_define([_m4_b], _m4_defn([_m4_bmatch]))_m4_b([$1], [$2], [$3])... # _m4_b([$1], [$m-1], [$m])_m4_b([], [], [$m+1]_m4_popdef([_m4_b])) # then invoke m4_unquote(_m4_b($@)), for concatenation with later text. m4_define([m4_bmatch], [m4_if([$#], 0, [m4_fatal([$0: too few arguments: $#])], [$#], 1, [m4_fatal([$0: too few arguments: $#: $1])], [$#], 2, [$2], [m4_pushdef([_m4_b], [m4_define([_m4_b], _m4_defn([_$0]))]_m4_for([3], m4_eval([($# + 1) / 2 * 2 - 1]), [2], [_$0_(], [)])[_m4_b([], [],]m4_dquote([$]m4_eval( [($# + 1) / 2 * 2]))[_m4_popdef([_m4_b]))])m4_unquote(_m4_b($@))])]) m4_define([_m4_bmatch], [m4_if(m4_bregexp([$1], [$2]), [-1], [], [[$3]m4_define([$0])])]) m4_define([_m4_bmatch_], [$0_([1], m4_decr([$1]), [$1])]) m4_define([_m4_bmatch__], [[_m4_b([$$1], [$$2], [$$3])]]) # m4_cond(TEST1, VAL1, IF-VAL1, TEST2, VAL2, IF-VAL2, ..., [DEFAULT]) # ------------------------------------------------------------------- # Similar to m4_if, except that each TEST is expanded when encountered. # If the expansion of TESTn matches the string VALn, the result is IF-VALn. # The result is DEFAULT if no tests passed. This macro allows # short-circuiting of expensive tests, where it pays to arrange quick # filter tests to run first. # # m4_cond already guarantees either 3*n or 3*n + 1 arguments, 1 <= n. # We only have to speed up _m4_cond, by building the temporary _m4_c: # m4_define([_m4_c], _m4_defn([m4_unquote]))_m4_c([m4_if(($1), [($2)], # [[$3]m4_define([_m4_c])])])_m4_c([m4_if(($4), [($5)], # [[$6]m4_define([_m4_c])])])..._m4_c([m4_if(($m-2), [($m-1)], # [[$m]m4_define([_m4_c])])])_m4_c([[$m+1]]_m4_popdef([_m4_c])) # We invoke m4_unquote(_m4_c($@)), for concatenation with later text. m4_define([_m4_cond], [m4_pushdef([_m4_c], [m4_define([_m4_c], _m4_defn([m4_unquote]))]_m4_for([2], m4_eval([$# / 3 * 3 - 1]), [3], [$0_(], [)])[_m4_c(]m4_dquote(m4_dquote( [$]m4_eval([$# / 3 * 3 + 1])))[_m4_popdef([_m4_c]))])m4_unquote(_m4_c($@))]) m4_define([_m4_cond_], [$0_(m4_decr([$1]), [$1], m4_incr([$1]))]) m4_define([_m4_cond__], [[_m4_c([m4_if(($$1), [($$2)], [[$$3]m4_define([_m4_c])])])]]) # m4_bpatsubsts(STRING, RE1, SUBST1, RE2, SUBST2, ...) # ---------------------------------------------------- # m4 equivalent of # # $_ = STRING; # s/RE1/SUBST1/g; # s/RE2/SUBST2/g; # ... # # m4_bpatsubsts already validated an odd number of arguments; we only # need to speed up _m4_bpatsubsts. To avoid nesting, we build the # temporary _m4_p: # m4_define([_m4_p], [$1])m4_define([_m4_p], # m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$2], [$3]))m4_define([_m4_p], # m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$4], [$5]))m4_define([_m4_p],... # m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$m-1], [$m]))m4_unquote( # _m4_defn([_m4_p])_m4_popdef([_m4_p])) m4_define([_m4_bpatsubsts], [m4_pushdef([_m4_p], [m4_define([_m4_p], ]m4_dquote([$]1)[)]_m4_for([3], [$#], [2], [$0_(], [)])[m4_unquote(_m4_defn([_m4_p])_m4_popdef([_m4_p]))])_m4_p($@)]) m4_define([_m4_bpatsubsts_], [$0_(m4_decr([$1]), [$1])]) m4_define([_m4_bpatsubsts__], [[m4_define([_m4_p], m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$$1], [$$2]))]]) # m4_shiftn(N, ...) # ----------------- # Returns ... shifted N times. Useful for recursive "varargs" constructs. # # m4_shiftn already validated arguments; we only need to speed up # _m4_shiftn. If N is 3, then we build the temporary _m4_s, defined as # ,[$5],[$6],...,[$m]_m4_popdef([_m4_s]) # before calling m4_shift(_m4_s($@)). m4_define([_m4_shiftn], [m4_if(m4_incr([$1]), [$#], [], [m4_pushdef([_m4_s], _m4_for(m4_eval([$1 + 2]), [$#], [1], [[,]m4_dquote($], [)])[_m4_popdef([_m4_s])])m4_shift(_m4_s($@))])]) # m4_do(STRING, ...) # ------------------ # This macro invokes all its arguments (in sequence, of course). It is # useful for making your macros more structured and readable by dropping # unnecessary dnl's and have the macros indented properly. # # Here, we use the temporary macro _m4_do, defined as # $1[]$2[]...[]$n[]_m4_popdef([_m4_do]) m4_define([m4_do], [m4_if([$#], [0], [], [m4_pushdef([_$0], _m4_for([1], [$#], [1], [$], [[[]]])[_m4_popdef([_$0])])_$0($@)])]) # m4_dquote_elt(ARGS) # ------------------- # Return ARGS as an unquoted list of double-quoted arguments. # # _m4_foreach to the rescue. m4_define([m4_dquote_elt], [m4_if([$#], [0], [], [[[$1]]_m4_foreach([,m4_dquote(], [)], $@)])]) # m4_reverse(ARGS) # ---------------- # Output ARGS in reverse order. # # Invoke _m4_r($@) with the temporary _m4_r built as # [$m], [$m-1], ..., [$2], [$1]_m4_popdef([_m4_r]) m4_define([m4_reverse], [m4_if([$#], [0], [], [$#], [1], [[$1]], [m4_pushdef([_m4_r], [[$$#]]_m4_for(m4_decr([$#]), [1], [-1], [[, ]m4_dquote($], [)])[_m4_popdef([_m4_r])])_m4_r($@)])]) # m4_map_args_pair(EXPRESSION, [END-EXPR = EXPRESSION], ARG...) # ------------------------------------------------------------- # Perform a pairwise grouping of consecutive ARGs, by expanding # EXPRESSION([ARG1], [ARG2]). If there are an odd number of ARGs, the # final argument is expanded with END-EXPR([ARGn]). # # Build the temporary macro _m4_map_args_pair, with the $2([$m+1]) # only output if $# is odd: # $1([$3], [$4])[]$1([$5], [$6])[]...$1([$m-1], # [$m])[]m4_default([$2], [$1])([$m+1])[]_m4_popdef([_m4_map_args_pair]) m4_define([m4_map_args_pair], [m4_if([$#], [0], [m4_fatal([$0: too few arguments: $#])], [$#], [1], [m4_fatal([$0: too few arguments: $#: $1])], [$#], [2], [], [$#], [3], [m4_default([$2], [$1])([$3])[]], [m4_pushdef([_$0], _m4_for([3], m4_eval([$# / 2 * 2 - 1]), [2], [_$0_(], [)])_$0_end( [1], [2], [$#])[_m4_popdef([_$0])])_$0($@)])]) m4_define([_m4_map_args_pair_], [$0_([1], [$1], m4_incr([$1]))]) m4_define([_m4_map_args_pair__], [[$$1([$$2], [$$3])[]]]) m4_define([_m4_map_args_pair_end], [m4_if(m4_eval([$3 & 1]), [1], [[m4_default([$$2], [$$1])([$$3])[]]])]) # m4_join(SEP, ARG1, ARG2...) # --------------------------- # Produce ARG1SEPARG2...SEPARGn. Avoid back-to-back SEP when a given ARG # is the empty string. No expansion is performed on SEP or ARGs. # # Use a self-modifying separator, since we don't know how many # arguments might be skipped before a separator is first printed, but # be careful if the separator contains $. _m4_foreach to the rescue. m4_define([m4_join], [m4_pushdef([_m4_sep], [m4_define([_m4_sep], _m4_defn([m4_echo]))])]dnl [_m4_foreach([_$0([$1],], [)], $@)_m4_popdef([_m4_sep])]) m4_define([_m4_join], [m4_if([$2], [], [], [_m4_sep([$1])[$2]])]) # m4_joinall(SEP, ARG1, ARG2...) # ------------------------------ # Produce ARG1SEPARG2...SEPARGn. An empty ARG results in back-to-back SEP. # No expansion is performed on SEP or ARGs. # # A bit easier than m4_join. _m4_foreach to the rescue. m4_define([m4_joinall], [[$2]m4_if(m4_eval([$# <= 2]), [1], [], [_m4_foreach([$1], [], m4_shift($@))])]) # m4_list_cmp(A, B) # ----------------- # Compare the two lists of integer expressions A and B. # # m4_list_cmp takes care of any side effects; we only override # _m4_list_cmp_raw, where we can safely expand lists multiple times. # First, insert padding so that both lists are the same length; the # trailing +0 is necessary to handle a missing list. Next, create a # temporary macro to perform pairwise comparisons until an inequality # is found. For example, m4_list_cmp([1], [1,2]) creates _m4_cmp as # m4_if(m4_eval([($1) != ($3)]), [1], [m4_cmp([$1], [$3])], # m4_eval([($2) != ($4)]), [1], [m4_cmp([$2], [$4])], # [0]_m4_popdef([_m4_cmp])) # then calls _m4_cmp([1+0], [0*2], [1], [2+0]) m4_define([_m4_list_cmp_raw], [m4_if([$1], [$2], 0, [_m4_list_cmp($1+0_m4_list_pad(m4_count($1), m4_count($2)), $2+0_m4_list_pad(m4_count($2), m4_count($1)))])]) m4_define([_m4_list_pad], [m4_if(m4_eval($1 < $2), [1], [_m4_for(m4_incr([$1]), [$2], [1], [,0*])])]) m4_define([_m4_list_cmp], [m4_pushdef([_m4_cmp], [m4_if(]_m4_for( [1], m4_eval([$# >> 1]), [1], [$0_(], [,]m4_eval([$# >> 1])[)])[ [0]_m4_popdef([_m4_cmp]))])_m4_cmp($@)]) m4_define([_m4_list_cmp_], [$0_([$1], m4_eval([$1 + $2]))]) m4_define([_m4_list_cmp__], [[m4_eval([($$1) != ($$2)]), [1], [m4_cmp([$$1], [$$2])], ]]) # m4_max(EXPR, ...) # m4_min(EXPR, ...) # ----------------- # Return the decimal value of the maximum (or minimum) in a series of # integer expressions. # # _m4_foreach to the rescue; we only need to replace _m4_minmax. Here, # we need a temporary macro to track the best answer so far, so that # the foreach expression is tractable. m4_define([_m4_minmax], [m4_pushdef([_m4_best], m4_eval([$2]))_m4_foreach( [m4_define([_m4_best], $1(_m4_best,], [))], m4_shift($@))]dnl [_m4_best[]_m4_popdef([_m4_best])]) # m4_set_add_all(SET, VALUE...) # ----------------------------- # Add each VALUE into SET. This is O(n) in the number of VALUEs, and # can be faster than calling m4_set_add for each VALUE. # # _m4_foreach to the rescue. If no deletions have occurred, then # avoid the speed penalty of m4_set_add. m4_define([m4_set_add_all], [m4_if([$#], [0], [], [$#], [1], [], [m4_define([_m4_set_size($1)], m4_eval(m4_set_size([$1]) + m4_len(_m4_foreach(m4_ifdef([_m4_set_cleanup($1)], [[m4_set_add]], [[_$0]])[([$1],], [)], $@))))])]) m4_define([_m4_set_add_all], [m4_ifdef([_m4_set([$1],$2)], [], [m4_define([_m4_set([$1],$2)], [1])m4_pushdef([_m4_set([$1])], [$2])-])])
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