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--All rights reserved.
--Copyright (C) 2007-2009, Gabriel Dos Reis.
--All rights reserved.
--
--Redistribution and use in source and binary forms, with or without
--modification, are permitted provided that the following conditions are
--met:
--
-- - Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
--
-- - Redistributions in binary form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in
-- the documentation and/or other materials provided with the
-- distribution.
--
-- - Neither the name of The Numerical ALgorithms Group Ltd. nor the
-- names of its contributors may be used to endorse or promote products
-- derived from this software without specific prior written permission.
--
--THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
--IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
--TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
--PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
--OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
--EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
--PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
--PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
--LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
--NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
--SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
)abbrev domain PATRES PatternMatchResult
++ Result returned by the pattern matcher
++ Author: Manuel Bronstein
++ Date Created: 28 Nov 1989
++ Date Last Updated: 5 Jul 1990
++ Description:
++ A PatternMatchResult is an object internally returned by the
++ pattern matcher; It is either a failed match, or a list of
++ matches of the form (var, expr) meaning that the variable var
++ matches the expression expr.
++ Keywords: pattern, matching.
-- not exported
PatternMatchResult(R:SetCategory, S:SetCategory): SetCategory with
failed? : % -> Boolean
++ failed?(r) tests if r is a failed match.
failed : () -> %
++ failed() returns a failed match.
new : () -> %
++ new() returns a new empty match result.
union : (%, %) -> %
++ union(a, b) makes the set-union of two match results.
getMatch : (Pattern R, %) -> Union(S, "failed")
++ getMatch(var, r) returns the expression that var matches
++ in the result r, and "failed" if var is not matched in r.
addMatch : (Pattern R, S, %) -> %
++ addMatch(var, expr, r) adds the match (var, expr) in r,
++ provided that expr satisfies the predicates attached to var,
++ and that var is not matched to another expression already.
insertMatch : (Pattern R, S, %) -> %
++ insertMatch(var, expr, r) adds the match (var, expr) in r,
++ without checking predicates or previous matches for var.
addMatchRestricted: (Pattern R, S, %, S) -> %
++ addMatchRestricted(var, expr, r, val) adds the match
++ (var, expr) in r,
++ provided that expr satisfies the predicates attached to var,
++ that var is not matched to another expression already,
++ and that either var is an optional pattern variable or that
++ expr is not equal to val (usually an identity).
destruct : % -> List Record(key:Symbol, entry:S)
++ destruct(r) returns the list of matches (var, expr) in r.
++ Error: if r is a failed match.
construct : List Record(key:Symbol, entry:S) -> %
++ construct([v1,e1],...,[vn,en]) returns the match result
++ containing the matches (v1,e1),...,(vn,en).
satisfy? : (%, Pattern R) -> Union(Boolean, "failed")
++ satisfy?(r, p) returns true if the matches satisfy the
++ top-level predicate of p, false if they don't, and "failed"
++ if not enough variables of p are matched in r to decide.
== add
LR ==> AssociationList(Symbol, S)
import PatternFunctions1(R, S)
Rep := Union(LR, "failed")
new() == empty()
failed() == "failed"
failed? x == x case "failed"
insertMatch(p, x, l) == concat([retract p, x], l::LR)
construct l == construct(l)$LR
destruct l == entries(l::LR)$LR
-- returns "failed" if not all the variables of the pred. are matched
satisfy?(r, p) ==
failed? r => false
lr := r::LR
lv := [if (u := search(v, lr)) case "failed" then return "failed"
else u::S for v in topPredicate(p).var]$List(S)
satisfy?(lv, p)
union(x, y) ==
failed? x or failed? y => failed()
removeDuplicates concat(x::LR, y::LR)
x = y ==
failed? x => failed? y
failed? y => false
x::LR =$LR y::LR
coerce(x:%):OutputForm ==
failed? x => "Does not match"::OutputForm
destruct(x)::OutputForm
addMatchRestricted(p, x, l, ident) ==
(not optional? p) and (x = ident) => failed()
addMatch(p, x, l)
addMatch(p, x, l) ==
failed?(l) or not(satisfy?(x, p)) => failed()
al := l::LR
sy := retract(p)@Symbol
(r := search(sy, al)) case "failed" => insertMatch(p, x, l)
r::S = x => l
failed()
getMatch(p, l) ==
failed? l => "failed"
search(retract(p)@Symbol, l::LR)
)abbrev package PATRES2 PatternMatchResultFunctions2
++ Lifts maps to pattern matching results
++ Author: Manuel Bronstein
++ Date Created: 1 Dec 1989
++ Date Last Updated: 14 Dec 1989
++ Description: Lifts maps to pattern matching results.
++ Keywords: pattern, matching.
PatternMatchResultFunctions2(R, A, B): Exports == Implementation where
R: SetCategory
A: SetCategory
B: SetCategory
Exports ==> with
map: (A -> B, PatternMatchResult(R, A)) -> PatternMatchResult(R, B)
++ map(f, [(v1,a1),...,(vn,an)]) returns the matching result
++ [(v1,f(a1)),...,(vn,f(an))].
Implementation ==> add
map(f, r) ==
failed? r => failed()
construct [[rec.key, f(rec.entry)] for rec in destruct r]
)abbrev domain PATLRES PatternMatchListResult
++ Result returned by the pattern matcher when using lists
++ Author: Manuel Bronstein
++ Date Created: 4 Dec 1989
++ Date Last Updated: 4 Dec 1989
++ Description:
++ A PatternMatchListResult is an object internally returned by the
++ pattern matcher when matching on lists.
++ It is either a failed match, or a pair of PatternMatchResult,
++ one for atoms (elements of the list), and one for lists.
++ Keywords: pattern, matching, list.
-- not exported
PatternMatchListResult(R:SetCategory, S:SetCategory, L:ListAggregate S):
SetCategory with
failed? : % -> Boolean
++ failed?(r) tests if r is a failed match.
failed : () -> %
++ failed() returns a failed match.
new : () -> %
++ new() returns a new empty match result.
makeResult: (PatternMatchResult(R,S), PatternMatchResult(R,L)) -> %
++ makeResult(r1,r2) makes the combined result [r1,r2].
atoms : % -> PatternMatchResult(R, S)
++ atoms(r) returns the list of matches that match atoms
++ (elements of the lists).
lists : % -> PatternMatchResult(R, L)
++ lists(r) returns the list of matches that match lists.
== add
Rep := Record(a:PatternMatchResult(R, S), l:PatternMatchResult(R, L))
new() == [new(), new()]
atoms r == r.a
lists r == r.l
failed() == [failed(), failed()]
failed? r == failed?(atoms r)
x = y == (atoms x = atoms y) and (lists x = lists y)
makeResult(r1, r2) ==
failed? r1 or failed? r2 => failed()
[r1, r2]
coerce(r:%):OutputForm ==
failed? r => atoms(r)::OutputForm
RecordPrint(r, Rep)$Lisp
)abbrev category PATMAB PatternMatchable
++ Category of sets that can be pattern-matched on
++ Author: Manuel Bronstein
++ Date Created: 28 Nov 1989
++ Date Last Updated: 15 Mar 1990
++ Description:
++ A set R is PatternMatchable over S if elements of R can
++ be matched to patterns over S.
++ Keywords: pattern, matching.
PatternMatchable(S:SetCategory): Category == SetCategory with
patternMatch: (%, Pattern S, PatternMatchResult(S, %)) ->
PatternMatchResult(S, %)
++ patternMatch(expr, pat, res) matches the pattern pat to the
++ expression expr. res contains the variables of pat which
++ are already matched and their matches (necessary for recursion).
++ Initially, res is just the result of \spadfun{new}
++ which is an empty list of matches.
)abbrev category FPATMAB FullyPatternMatchable
++ Category of sets that can be pattern-matched on
++ Author: Manuel Bronstein
++ Date Created: 28 Nov 1989
++ Date Last Updated: 29 Nov 1989
++ Description:
++ A set S is PatternMatchable over R if S can lift the
++ pattern-matching functions of S over the integers and float
++ to itself (necessary for matching in towers).
++ Keywords: pattern, matching.
FullyPatternMatchable(R:Type): Category == Type with
if R has PatternMatchable Integer then PatternMatchable Integer
if R has PatternMatchable Float then PatternMatchable Float
)abbrev package PMSYM PatternMatchSymbol
++ Pattern matching on symbols
++ Author: Manuel Bronstein
++ Date Created: 9 Jan 1990
++ Date Last Updated: 20 June 1991
++ Description:
++ This package provides pattern matching functions on symbols.
++ Keywords: pattern, matching, symbol.
PatternMatchSymbol(S:SetCategory): with
patternMatch: (Symbol, Pattern S, PatternMatchResult(S, Symbol)) ->
PatternMatchResult(S, Symbol)
++ patternMatch(expr, pat, res) matches the pattern pat to the
++ expression expr; res contains the variables of pat which
++ are already matched and their matches (necessary for recursion).
== add
import TopLevelPatternMatchControl
patternMatch(s, p, l) ==
generic? p => addMatch(p, s, l)
constant? p =>
((u := retractIfCan(p)@Union(Symbol, "failed")) case Symbol)
and (u::Symbol) = s => l
failed()
failed()
)abbrev package PMKERNEL PatternMatchKernel
++ Pattern matching on kernels
++ Author: Manuel Bronstein
++ Date Created: 12 Jan 1990
++ Date Last Updated: 4 May 1992
++ Description:
++ This package provides pattern matching functions on kernels.
++ Keywords: pattern, matching, kernel.
PatternMatchKernel(S, E): Exports == Implementation where
S: SetCategory
E: Join(SetCategory, RetractableTo Kernel %,
ConvertibleTo Pattern S, PatternMatchable S)
PAT ==> Pattern S
PRS ==> PatternMatchResult(S, E)
POWER ==> '%power
NTHRT ==> 'nthRoot
Exports ==> with
patternMatch: (Kernel E, PAT, PRS) -> PRS
++ patternMatch(f(e1,...,en), pat, res) matches the pattern pat
++ to \spad{f(e1,...,en)}; res contains the variables of pat which
++ are already matched and their matches.
Implementation ==> add
patternMatchArg : (List E, List PAT, PRS) -> PRS
patternMatchInner: (Kernel E, PAT, PRS) -> Union(PRS, "failed")
-- matches the ordered lists ls and lp.
patternMatchArg(ls, lp, l) ==
#ls ~= #lp => failed()
for p in lp for s in ls repeat
generic? p and failed?(l := addMatch(p,s,l)) => return failed()
for p in lp for s in ls repeat
not(generic? p) and failed?(l := patternMatch(s, p, l)) =>
return failed()
l
patternMatchInner(s, p, l) ==
generic? p => addMatch(p, s::E, l)
(u := isOp p) case Record(op:BasicOperator, arg: List PAT) =>
ur := u::Record(op:BasicOperator, arg: List PAT)
ur.op = operator s => patternMatchArg(argument s, ur.arg, l)
failed()
constant? p =>
((v := retractIfCan(p)@Union(Symbol, "failed")) case Symbol)
and ((w := symbolIfCan s) case Symbol) and
(v::Symbol = w::Symbol) => l
failed()
"failed"
if E has Monoid then
patternMatchMonoid: (Kernel E, PAT, PRS) -> Union(PRS, "failed")
patternMatchOpt : (E, List PAT, PRS, E) -> PRS
patternMatchOpt(x, lp, l, id) ==
import PAT
(u := optpair lp) case List(PAT) =>
failed?(l := addMatch(first(u::List(PAT)), id, l)) => failed()
patternMatch(x, second(u::List(PAT)), l)
failed()
patternMatchMonoid(s, p, l) ==
(u := patternMatchInner(s, p, l)) case PRS => u::PRS
(v := isPower p) case Record(val:PAT, exponent:PAT) =>
vr := v::Record(val:PAT, exponent: PAT)
is?(op := operator s, POWER) =>
patternMatchArg(argument s, [vr.val, vr.exponent], l)
is?(op,NTHRT) and ((r := recip(second(arg := argument s))) case E) =>
patternMatchArg([first arg, r::E], [vr.val, vr.exponent], l)
optional?(vr.exponent) =>
failed?(l := addMatch(vr.exponent, 1, l)) => failed()
patternMatch(s::E, vr.val, l)
failed()
(w := isTimes p) case List(PAT) =>
patternMatchOpt(s::E, w::List(PAT), l, 1)
"failed"
if E has AbelianMonoid then
patternMatch(s, p, l) ==
(u := patternMatchMonoid(s, p, l)) case PRS => u::PRS
(w := isPlus p) case List(PAT) =>
patternMatchOpt(s::E, w::List(PAT), l, 0)
failed()
else
patternMatch(s, p, l) ==
(u := patternMatchMonoid(s, p, l)) case PRS => u::PRS
failed()
else
patternMatch(s, p, l) ==
(u := patternMatchInner(s, p, l)) case PRS => u::PRS
failed()
)abbrev package PMDOWN PatternMatchPushDown
++ Pattern matching in towers
++ Author: Manuel Bronstein
++ Date Created: 1 Dec 1989
++ Date Last Updated: 16 August 1995
++ Description:
++ This packages provides tools for matching recursively
++ in type towers.
++ Keywords: pattern, matching, quotient, field.
PatternMatchPushDown(S, A, B): Exports == Implementation where
S: SetCategory
A: PatternMatchable S
B: Join(SetCategory, RetractableTo A)
PAT ==> Pattern S
PRA ==> PatternMatchResult(S, A)
PRB ==> PatternMatchResult(S, B)
REC ==> Record(pat:PAT, res:PRA)
Exports ==> with
fixPredicate: (B -> Boolean) -> (A -> Boolean)
++ fixPredicate(f) returns g defined by g(a) = f(a::B);
patternMatch: (A, PAT, PRB) -> PRB
++ patternMatch(expr, pat, res) matches the pattern pat to the
++ expression expr; res contains the variables of pat which
++ are already matched and their matches.
++ Note: this function handles type towers by changing the predicates
++ and calling the matching function provided by \spad{A}.
Implementation ==> add
import PatternMatchResultFunctions2(S, A, B)
fixPred : Any -> Union(Any, "failed")
inA : (PAT, PRB) -> Union(List A, "failed")
fixPredicates: (PAT, PRB, PRA) -> Union(REC, "failed")
fixList:(List PAT -> PAT, List PAT, PRB, PRA) -> Union(REC,"failed")
fixPredicate f == f(#1::B)
patternMatch(a, p, l) ==
(u := fixPredicates(p, l, new())) case "failed" => failed()
union(l, map(#1::B, patternMatch(a, (u::REC).pat, (u::REC).res)))
inA(p, l) ==
(u := getMatch(p, l)) case "failed" => empty()
(r := retractIfCan(u::B)@Union(A, "failed")) case A => [r::A]
"failed"
fixList(fn, l, lb, la) ==
ll:List(PAT) := empty()
for x in l repeat
(f := fixPredicates(x, lb, la)) case "failed" => return "failed"
ll := concat((f::REC).pat, ll)
la := (f::REC).res
[fn ll, la]
fixPred f ==
(u:= retractIfCan(f)$AnyFunctions1(B -> Boolean)) case "failed" =>
"failed"
g := fixPredicate(u::(B -> Boolean))
coerce(g)$AnyFunctions1(A -> Boolean)
fixPredicates(p, lb, la) ==
(r:=retractIfCan(p)@Union(S,"failed")) case S or quoted? p =>[p,la]
(u := isOp p) case Record(op:BasicOperator, arg:List PAT) =>
ur := u::Record(op:BasicOperator, arg:List PAT)
fixList((ur.op) #1, ur.arg, lb, la)
(us := isPlus p) case List(PAT) =>
fixList(reduce("+", #1), us::List(PAT), lb, la)
(us := isTimes p) case List(PAT) =>
fixList(reduce("*", #1), us::List(PAT), lb, la)
(v := isQuotient p) case Record(num:PAT, den:PAT) =>
vr := v::Record(num:PAT, den:PAT)
(fn := fixPredicates(vr.num, lb, la)) case "failed" => "failed"
la := (fn::REC).res
(fd := fixPredicates(vr.den, lb, la)) case "failed" => "failed"
[(fn::REC).pat / (fd::REC).pat, (fd::REC).res]
(w:= isExpt p) case Record(val:PAT,exponent:NonNegativeInteger) =>
wr := w::Record(val:PAT, exponent: NonNegativeInteger)
(f := fixPredicates(wr.val, lb, la)) case "failed" => "failed"
[(f::REC).pat ** wr.exponent, (f::REC).res]
(uu := isPower p) case Record(val:PAT, exponent:PAT) =>
uur := uu::Record(val:PAT, exponent: PAT)
(fv := fixPredicates(uur.val, lb, la)) case "failed" => "failed"
la := (fv::REC).res
(fe := fixPredicates(uur.exponent, lb, la)) case "failed" =>
"failed"
[(fv::REC).pat ** (fe::REC).pat, (fe::REC).res]
generic? p =>
(ua := inA(p, lb)) case "failed" => "failed"
lp := [if (h := fixPred g) case Any then h::Any else
return "failed" for g in predicates p]$List(Any)
q := setPredicates(patternVariable(retract p, constant? p,
optional? p, multiple? p), lp)
[q, (empty?(ua::List A) => la; insertMatch(q,first(ua::List A), la))]
error "Should not happen"
)abbrev package PMTOOLS PatternMatchTools
++ Tools for the pattern matcher
++ Author: Manuel Bronstein
++ Date Created: 13 Mar 1990
++ Date Last Updated: 4 February 1992
++ Description:
++ This package provides tools for the pattern matcher.
++ Keywords: pattern, matching, tools.
PatternMatchTools(S, R, P): Exports == Implementation where
S: SetCategory
R: Ring
P: Join(Ring, ConvertibleTo Pattern S, RetractableTo R)
PAT ==> Pattern S
PRS ==> PatternMatchResult(S, P)
REC ==> Record(res:PRS, s:List P)
RC ==> Record(pat:List PAT, s:List P)
Exports ==> with
patternMatch: (List P, List PAT, List P -> P, PRS,
(P, PAT, PRS) -> PRS) -> PRS
++ patternMatch(lsubj, lpat, op, res, match) matches the list
++ of patterns lpat to the list of subjects lsubj, allowing for
++ commutativity; op is the operator such that op(lpat) should
++ match op(lsubj) at the end, r contains the previous matches,
++ and match is a pattern-matching function on P.
patternMatchTimes: (List P, List PAT, PRS,
(P, PAT, PRS) -> PRS) -> PRS
++ patternMatchTimes(lsubj, lpat, res, match) matches the
++ product of patterns \spad{reduce(*,lpat)}
++ to the product of subjects \spad{reduce(*,lsubj)};
++ r contains the previous matches
++ and match is a pattern-matching function on P.
Implementation ==> add
import PatternFunctions1(S, P)
preprocessList: (PAT, List P, PRS) -> Union(List P, "failed")
selBestGen : List PAT -> List PAT
negConstant : List P -> Union(P, "failed")
findMatch : (PAT, List P, PRS, P, (P, PAT, PRS) -> PRS) -> REC
tryToMatch : (List PAT, REC, P, (P, PAT, PRS) -> PRS) ->
Union(REC, "failed")
filterMatchedPatterns: (List PAT, List P, PRS) -> Union(RC, "failed")
mn1 := convert(-1::P)@Pattern(S)
negConstant l ==
if R has OrderedSet then
for x in l repeat
((r := retractIfCan(x)@Union(R, "failed")) case R) and
(r::R) < 0 => return x
"failed"
-- tries to match the list of patterns lp to the list of subjects rc.s
-- with rc.res being the list of existing matches.
-- updates rc with the new result and subjects still to match
tryToMatch(lp, rc, ident, pmatch) ==
rec:REC := [l := rc.res, ls := rc.s]
for p in lp repeat
rec := findMatch(p, ls, l, ident, pmatch)
failed?(l := rec.res) => return "failed"
ls := rec.s
rec
-- handles -1 in the pattern list.
patternMatchTimes(ls, lp, l, pmatch) ==
member?(mn1, lp) =>
(u := negConstant ls) case "failed" => failed()
if (u::P ~= -1::P) then ls := concat(-u::P, ls)
patternMatch(remove(u::P,ls), remove(mn1,lp), */#1, l, pmatch)
patternMatch(ls, lp, */#1, l, pmatch)
-- finds a match for p in ls, try not to match to a "bad" value
findMatch(p, ls, l, ident, pmatch) ==
bad:List(P) :=
generic? p => setIntersection(badValues p, ls)
empty()
l1:PRS := failed()
t : P
for x in setDifference(ls, bad)
while (t := x; failed?(l1 := pmatch(x, p, l))) repeat nil
failed? l1 =>
for x in bad
while (t := x; failed?(l1 := pmatch(x, p, l))) repeat nil
failed? l1 => [addMatchRestricted(p, ident, l, ident), ls]
[l1, remove(t, ls)]
[l1, remove(t, ls)]
-- filters out pattern if it's generic and already matched.
preprocessList(pattern, ls, l) ==
generic? pattern =>
(u := getMatch(pattern, l)) case P =>
member?(u::P, ls) => [u::P]
"failed"
empty()
empty()
-- take out already matched generic patterns
filterMatchedPatterns(lp, ls, l) ==
for p in lp repeat
(rc := preprocessList(p, ls, l)) case "failed" => return "failed"
if not empty?(rc::List(P)) then
lp := remove(p, lp)
ls := remove(first(rc::List(P)), ls)
[lp, ls]
-- select a generic pattern with no predicate if possible
selBestGen l ==
ans := empty()$List(PAT)
for p in l | generic? p repeat
ans := [p]
not hasPredicate? p => return ans
ans
-- matches unordered lists ls and lp
patternMatch(ls, lp, op, l, pmatch) ==
ident := op empty()
(rc := filterMatchedPatterns(lp, ls, l)) case "failed" => return failed()
lp := (rc::RC).pat
ls := (rc::RC).s
empty? lp => l
#(lpm := select(optional?, lp)) > 1 =>
error "More than one optional pattern in sum/product"
(#ls + #lpm) < #lp => failed()
if (not empty? lpm) and (#ls + 1 = #lp) then
lp := remove(first lpm, lp)
failed?(l := addMatch(first lpm, ident, l)) => return l
#(lpm := select(multiple?, lp)) > 1 =>
error "More than one expandable pattern in sum/product"
#ls > #lp and empty? lpm and empty?(lpm := selBestGen lp) =>
failed()
if not empty? lpm then lp := remove(first lpm, lp)
-- this is the order in which we try to match predicates
-- l1 = constant patterns (i.e. 'x, or sin('x))
l1 := select(constant?, lp)
-- l2 = patterns with a predicate attached to them
l2 := select(hasPredicate? #1 and not constant? #1, lp)
-- l3 = non-generic patterns without predicates
l3 := sort!(depth(#1) > depth(#2),
select(not(hasPredicate? #1 or generic? #1 or constant? #1),lp))
-- l4 = generic patterns with predicates
l4 := select(generic? #1 and
not(hasPredicate? #1 or constant? #1), lp)
rec:REC := [l, ls]
(u := tryToMatch(l1, rec, ident, pmatch)) case "failed" =>
failed()
(u := tryToMatch(l2, u::REC, ident, pmatch)) case "failed" =>
failed()
(u := tryToMatch(l3, u::REC, ident, pmatch)) case "failed" =>
failed()
rec := u::REC
(rc := filterMatchedPatterns(l4,rec.s,rec.res)) case "failed" => failed()
rec := [rec.res, (rc::RC).s]
(u := tryToMatch((rc::RC).pat,rec,ident,pmatch)) case "failed" => failed()
rec := u::REC
l := rec.res
ls := rec.s
empty? lpm =>
empty? ls => l
failed()
addMatch(first lpm, op ls, l)
)abbrev package PMLSAGG PatternMatchListAggregate
++ Pattern matching for list aggregates
++ Author: Manuel Bronstein
++ Date Created: 4 Dec 1989
++ Date Last Updated: 29 Jun 1990
++ Description:
++ This package provides pattern matching functions on lists.
++ Keywords: pattern, matching, list.
PatternMatchListAggregate(S, R, L): Exports == Implementation where
S: SetCategory
R: PatternMatchable S
L: ListAggregate R
PLR ==> PatternMatchListResult(S, R, L)
Exports ==> with
patternMatch: (L, Pattern S, PLR) -> PLR
++ patternMatch(l, pat, res) matches the pattern pat to the
++ list l; res contains the variables of pat which
++ are already matched and their matches.
Implementation ==> add
match: (L, List Pattern S, PLR, Boolean) -> PLR
patternMatch(l, p, r) ==
(u := isList p) case "failed" => failed()
match(l, u::List Pattern S, r, true)
match(l, lp, r, new?) ==
empty? lp =>
empty? l => r
failed()
multiple?(p0 := first lp) =>
empty? rest lp =>
if not new? then l := reverse! l
makeResult(atoms r, addMatchRestricted(p0,l,lists r,empty()))
new? => match(reverse l, reverse lp, r, false)
error "Only one multiple pattern allowed in list"
empty? l => failed()
failed?(r := makeResult(patternMatch(first l,p0,atoms r),lists r))
=> failed()
match(rest l, rest lp, r, new?)
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