// An instruction executed by the NFA
type Inst interface {
Type() int; // the type of this instruction: CHAR, ANY, etc.
- Next() int; // the index of the instruction to execute after this one
- SetNext(i int);
+ Next() Inst; // the instruction to execute after this one
+ SetNext(i Inst);
Print(ind string);
}
expr string; // the original expression
ch *chan<- *RE; // reply channel when we're done
error *os.Error; // compile- or run-time error; nil if OK
- ninst int;
- inst *[]Inst;
start Inst;
}
// --- START start of program
type Start struct {
- this int;
- next int;
+ next Inst;
}
func (start *Start) Type() int { return START }
-func (start *Start) Next() int { return start.next }
-func (start *Start) SetNext(i int) { start.next = i }
+func (start *Start) Next() Inst { return start.next }
+func (start *Start) SetNext(i Inst) { start.next = i }
func (start *Start) Print(ind string) { print(ind, "start") }
// --- END end of program
type End struct {
- this int;
- next int;
+ next Inst;
}
func (end *End) Type() int { return END }
-func (end *End) Next() int { return end.next }
-func (end *End) SetNext(i int) { end.next = i }
+func (end *End) Next() Inst { return end.next }
+func (end *End) SetNext(i Inst) { end.next = i }
func (end *End) Print(ind string) { print(ind, "end") }
// --- BOT beginning of text
type Bot struct {
- this int;
- next int;
+ next Inst;
}
func (bot *Bot) Type() int { return BOT }
-func (bot *Bot) Next() int { return bot.next }
-func (bot *Bot) SetNext(i int) { bot.next = i }
+func (bot *Bot) Next() Inst { return bot.next }
+func (bot *Bot) SetNext(i Inst) { bot.next = i }
func (bot *Bot) Print(ind string) { print(ind, "bot") }
// --- EOT end of text
type Eot struct {
- this int;
- next int;
+ next Inst;
}
func (eot *Eot) Type() int { return EOT }
-func (eot *Eot) Next() int { return eot.next }
-func (eot *Eot) SetNext(i int) { eot.next = i }
+func (eot *Eot) Next() Inst { return eot.next }
+func (eot *Eot) SetNext(i Inst) { eot.next = i }
func (eot *Eot) Print(ind string) { print(ind, "eot") }
// --- CHAR a regular character
type Char struct {
- this int;
- next int;
+ next Inst;
char int;
set bool;
}
func (char *Char) Type() int { return CHAR }
-func (char *Char) Next() int { return char.next }
-func (char *Char) SetNext(i int) { char.next = i }
+func (char *Char) Next() Inst { return char.next }
+func (char *Char) SetNext(i Inst) { char.next = i }
func (char *Char) Print(ind string) { print(ind, "char ", string(char.char)) }
func NewChar(char int) *Char {
// --- ANY any character
type Any struct {
- this int;
- next int;
+ next Inst;
}
func (any *Any) Type() int { return ANY }
-func (any *Any) Next() int { return any.next }
-func (any *Any) SetNext(i int) { any.next = i }
+func (any *Any) Next() Inst { return any.next }
+func (any *Any) SetNext(i Inst) { any.next = i }
func (any *Any) Print(ind string) { print(ind, "any") }
// --- BRA parenthesized expression
type Bra struct {
- this int;
- next int;
+ next Inst;
+ n int; // subexpression number
}
func (bra *Bra) Type() int { return BRA }
-func (bra *Bra) Next() int { return bra.next }
-func (bra *Bra) SetNext(i int) { bra.next = i }
+func (bra *Bra) Next() Inst { return bra.next }
+func (bra *Bra) SetNext(i Inst) { bra.next = i }
func (bra *Bra) Print(ind string) { print(ind , "bra"); }
// --- EBRA end of parenthesized expression
type Ebra struct {
- this int;
- next int;
+ next Inst;
n int; // subexpression number
}
func (ebra *Ebra) Type() int { return BRA }
-func (ebra *Ebra) Next() int { return ebra.next }
-func (ebra *Ebra) SetNext(i int) { ebra.next = i }
+func (ebra *Ebra) Next() Inst { return ebra.next }
+func (ebra *Ebra) SetNext(i Inst) { ebra.next = i }
func (ebra *Ebra) Print(ind string) { print(ind , "ebra ", ebra.n); }
// --- ALT alternation
type Alt struct {
- this int;
- next int;
- left int; // other branch
+ next Inst;
+ left Inst; // other branch
}
func (alt *Alt) Type() int { return ALT }
-func (alt *Alt) Next() int { return alt.next }
-func (alt *Alt) SetNext(i int) { alt.next = i }
+func (alt *Alt) Next() Inst { return alt.next }
+func (alt *Alt) SetNext(i Inst) { alt.next = i }
func (alt *Alt) Print(ind string) { print(ind , "alt(", alt.left, ")"); }
// --- NOP no operation
type Nop struct {
- this int;
- next int;
+ next Inst;
}
func (nop *Nop) Type() int { return NOP }
-func (nop *Nop) Next() int { return nop.next }
-func (nop *Nop) SetNext(i int) { nop.next = i }
+func (nop *Nop) Next() Inst { return nop.next }
+func (nop *Nop) SetNext(i Inst) { nop.next = i }
func (nop *Nop) Print(ind string) { print(ind, "nop") }
-
-func (re *RE) AddInst(inst Inst) int {
- if re.ninst >= cap(re.inst) {
- panic("write the code to grow inst")
- }
- re.inst[re.ninst] = inst;
- i := re.ninst;
- re.ninst++;
- inst.SetNext(re.ninst);
- return i;
-}
-
// report error and exit compiling/executing goroutine
func (re *RE) Error(err *os.Error) {
re.error = err;
type Parser struct {
re *RE;
- nbra int;
+ nbra int; // number of brackets in expression, for subexpressions
+ nlpar int; // number of unclosed lpars
pos int;
ch int;
}
*/
-func (p *Parser) Regexp() (start, end int)
+func (p *Parser) Regexp() (start, end Inst)
+
+var NULL Inst
+type BUGinter interface{}
-const NULL = -1
+// same as i == NULL. TODO: remove when 6g lets me do i == NULL
+func isNULL(i Inst) bool {
+ return sys.BUG_intereq(i.(BUGinter), NULL.(BUGinter))
+}
+
+// same as i == j. TODO: remove when 6g lets me do i == j
+func isEQ(i,j Inst) bool {
+ return sys.BUG_intereq(i.(BUGinter), j.(BUGinter))
+}
func special(c int) bool {
s := `\.+*?()|[-]`;
return false
}
-func (p *Parser) Term() (start, end int) {
+func (p *Parser) Term() (start, end Inst) {
switch c := p.c(); c {
case '|', EOF:
return NULL, NULL;
case '*', '+', '|':
p.re.Error(ErrBareClosure);
case ')':
- p.re.Error(ErrUnmatchedRpar);
+ if p.nlpar == 0 {
+ p.re.Error(ErrUnmatchedRpar);
+ }
+ return NULL, NULL;
case '.':
p.nextc();
- start = p.re.AddInst(new(Any));
+ start = new(Any);
return start, start;
case '(':
p.nextc();
+ p.nlpar++;
start, end = p.Regexp();
if p.c() != ')' {
p.re.Error(ErrUnmatchedLpar);
}
+ p.nlpar--;
p.nextc();
p.nbra++;
bra := new(Bra);
- brai := p.re.AddInst(bra);
ebra := new(Ebra);
- ebrai := p.re.AddInst(ebra);
+ bra.n = p.nbra;
ebra.n = p.nbra;
- if start == NULL {
- if end != NULL { p.re.Error(ErrInternal) }
- start = ebrai
+ if isNULL(start) {
+ if !isNULL(end) { p.re.Error(ErrInternal) }
+ start = ebra
} else {
- p.re.inst[end].SetNext(ebrai);
+ end.SetNext(ebra);
}
bra.SetNext(start);
- return brai, ebrai;
+ return bra, ebra;
case '\\':
c = p.nextc();
switch {
fallthrough;
default:
p.nextc();
- start = p.re.AddInst(NewChar(c));
+ start = NewChar(c);
return start, start
}
panic("unreachable");
}
-func (p *Parser) Closure() (start, end int) {
+func (p *Parser) Closure() (start, end Inst) {
start, end = p.Term();
- if start == NULL {
+ if isNULL(start) {
return start, end
}
switch p.c() {
case '*':
// (start,end)*:
alt := new(Alt);
- alti := p.re.AddInst(alt);
- p.re.inst[end].SetNext(alti); // after end, do alt
+ end.SetNext(alt); // after end, do alt
alt.left = start; // alternate brach: return to start
- start = alti; // alt becomes new (start, end)
- end = alti;
+ start = alt; // alt becomes new (start, end)
+ end = alt;
case '+':
// (start,end)+:
alt := new(Alt);
- alti := p.re.AddInst(alt);
- p.re.inst[end].SetNext(alti); // after end, do alt
+ end.SetNext(alt); // after end, do alt
alt.left = start; // alternate brach: return to start
- end = alti; // start is unchanged; end is alt
+ end = alt; // start is unchanged; end is alt
case '?':
// (start,end)?:
alt := new(Alt);
- alti := p.re.AddInst(alt);
nop := new(Nop);
- nopi := p.re.AddInst(nop);
alt.left = start; // alternate branch is start
- alt.next = nopi; // follow on to nop
- p.re.inst[end].SetNext(nopi); // after end, go to nop
- start = alti; // start is now alt
- end = nopi; // end is nop pointed to by both branches
+ alt.next = nop; // follow on to nop
+ end.SetNext(nop); // after end, go to nop
+ start = alt; // start is now alt
+ end = nop; // end is nop pointed to by both branches
default:
return start, end;
}
return start, end;
}
-func (p *Parser) Concatenation() (start, end int) {
+func (p *Parser) Concatenation() (start, end Inst) {
start, end = NULL, NULL;
for {
+ switch p.c() {
+ case '|', ')', EOF:
+ if isNULL(start) { // this is the empty string
+ nop := new(Nop);
+ return nop, nop;
+ }
+ return start, end;
+ }
nstart, nend := p.Closure();
switch {
- case nstart == NULL: // end of this concatenation
+ case isNULL(nstart): // end of this concatenation
return start, end;
- case start == NULL: // this is first element of concatenation
+ case isNULL(start): // this is first element of concatenation
start, end = nstart, nend;
default:
- p.re.inst[end].SetNext(nstart);
+ end.SetNext(nstart);
end = nend;
}
}
panic("unreachable");
}
-func (p *Parser) Regexp() (start, end int) {
+func (p *Parser) Regexp() (start, end Inst) {
start, end = p.Concatenation();
- if start == NULL {
+ if isNULL(start) {
return NULL, NULL
}
for {
p.nextc();
nstart, nend := p.Concatenation();
// xyz|(nothing) is xyz or nop
- if nstart == NULL {
- nopi := p.re.AddInst(new(Nop));
- nstart, nend = nopi, nopi;
+ if isNULL(nstart) {
+ nop := new(Nop);
+ nstart, nend = nop, nop;
}
alt := new(Alt);
- alti := p.re.AddInst(alt);
alt.left = start;
alt.next = nstart;
nop := new(Nop);
- nopi := p.re.AddInst(nop);
- p.re.inst[end].SetNext(nopi);
- p.re.inst[nend].SetNext(nopi);
- start, end = alti, nopi;
+ end.SetNext(nop);
+ nend.SetNext(nop);
+ start, end = alt, nop;
}
}
panic("unreachable");
}
-func (re *RE) UnNop(i int) int {
- for re.inst[i].Type() == NOP {
- i = re.inst[i].Next()
+func UnNop(i Inst) Inst {
+ for i.Type() == NOP {
+ i = i.Next()
}
return i
}
-func (re *RE) EliminateNops() {
- for i := 0; i < re.ninst - 1; i++ { // last one is END
- inst := re.inst[i];
- inst.SetNext(re.UnNop(inst.Next()));
- if inst.Type() == ALT {
- alt := inst.(*Alt);
- alt.left = re.UnNop(alt.left)
+func (re *RE) EliminateNops(start Inst) {
+ for i := start; i.Type() != END; i = i.Next() { // last one is END
+ i.SetNext(UnNop(i.Next()));
+ if i.Type() == ALT {
+ alt := i.(*Alt);
+ alt.left = UnNop(alt.left);
+ re.EliminateNops(alt.left);
}
}
}
+// use a 'done' array to know where we've already printed.
+// the output is not pretty but it is serviceable.
+func (re *RE) Dump(ind string, inst Inst, done *[]Inst) {
+ // see if we've been here, and mark it
+ for i := 0; i < len(done); i++ {
+ if isEQ(inst, done[i]) {
+ print(ind, inst, ": -> ", inst.Next(), "...\n");
+ return;
+ }
+ }
+ slot := len(done);
+ done= done[0:slot+1];
+ done[slot] = inst;
+
+ if isNULL(inst) {
+ println("NULL");
+ return;
+ }
+ if inst.Type() == END { print(inst, ": END\n"); return }
+ print(ind, inst, ": ");
+ inst.Print("");
+ print(" -> ", inst.Next(), "\n");
+ switch inst.Type() {
+ case END:
+ return;
+ case ALT:
+ re.Dump(ind + "\t", inst.(*Alt).left, done);
+ }
+ re.Dump(ind, inst.Next(), done);
+}
+
+func (re *RE) DumpAll() {
+ re.Dump("", re.start, new([]Inst, 1000)[0:0]);
+}
+
func (re *RE) DoParse() {
parser := NewParser(re);
start := new(Start);
- starti := re.AddInst(start);
s, e := parser.Regexp();
- if s == NULL {
- if e != NULL { re.Error(ErrInternal) }
- e = starti;
+ if isNULL(s) {
+ if !isNULL(e) { re.Error(ErrInternal) }
+ e = start;
}
start.next = s;
- re.inst[e].SetNext(re.AddInst(new(End)));
+ re.start = start;
+ e.SetNext(new(End));
- for i := 0; i < re.ninst; i++ {
- inst := re.inst[i];
- print(i, ":\t");
- inst.Print("\t");
- print(" -> ", inst.Next(), "\n");
- }
+ re.DumpAll();
println();
- re.EliminateNops();
+ re.EliminateNops(re.start);
- for i := 0; i < re.ninst; i++ {
- inst := re.inst[i];
- print(i, ":\t");
- inst.Print("\t");
- print(" -> ", inst.Next(), "\n");
- }
+ re.DumpAll();
println();
re.Error(ErrUnimplemented);
func Compiler(str string, ch *chan *RE) {
re := new(RE);
- re.inst = new([]Inst, 100);
re.expr = str;
re.ch = ch;
re.DoParse();