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regexp: simplify code for brackets, per rsc suggestion
R=rsc CC=golang-dev https://golang.org/cl/3545044
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@ -98,8 +98,7 @@ const (
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iCharClass // [a-z] character class
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iAny // '.' any character including newline
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iNotNL // [^\n] special case: any character but newline
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iBra // '(' parenthesized expression
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iEbra // ')'; end of '(' parenthesized expression
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iBra // '(' parenthesized expression: 2*braNum for left, 2*braNum+1 for right
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iAlt // '|' alternation
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iNop // do nothing; makes it easy to link without patching
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)
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@ -135,9 +134,11 @@ func (i *instr) print() {
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case iNotNL:
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print("notnl")
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case iBra:
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print("bra", i.braNum)
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case iEbra:
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print("ebra", i.braNum)
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if i.braNum&1 == 0 {
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print("bra", i.braNum/2)
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} else {
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print("ebra", i.braNum/2)
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}
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case iAlt:
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print("alt(", i.left.index, ")")
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case iNop:
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@ -391,12 +392,10 @@ func (p *parser) term() (start, end *instr) {
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}
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p.nlpar--
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p.nextc()
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bra := &instr{kind: iBra}
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bra := &instr{kind: iBra, braNum: 2 * nbra}
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p.re.add(bra)
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ebra := &instr{kind: iEbra}
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ebra := &instr{kind: iBra, braNum: 2*nbra + 1}
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p.re.add(ebra)
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bra.braNum = nbra
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ebra.braNum = nbra
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if start == nil {
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if end == nil {
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p.error(ErrInternal)
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@ -709,13 +708,7 @@ func (a *matchArena) addState(s []state, inst *instr, prefixed bool, match *matc
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}
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return s
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case iBra:
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n := inst.braNum
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match.m[2*n] = pos
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s = a.addState(s, inst.next, prefixed, match, pos, end)
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return s
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case iEbra:
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n := inst.braNum
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match.m[2*n+1] = pos
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match.m[inst.braNum] = pos
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s = a.addState(s, inst.next, prefixed, match, pos, end)
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return s
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}
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@ -821,7 +814,6 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
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s[out] = arena.addState(s[out], st.inst.next, st.prefixed, st.match, pos, end)
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}
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case iBra:
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case iEbra:
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case iAlt:
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case iEnd:
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// choose leftmost longest
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