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-rw-r--r--grammar/parsing_table.go486
1 files changed, 486 insertions, 0 deletions
diff --git a/grammar/parsing_table.go b/grammar/parsing_table.go
new file mode 100644
index 0000000..903f95a
--- /dev/null
+++ b/grammar/parsing_table.go
@@ -0,0 +1,486 @@
+package grammar
+
+import (
+ "fmt"
+ "io"
+ "strings"
+)
+
+type ActionType string
+
+const (
+ ActionTypeShift = ActionType("shift")
+ ActionTypeReduce = ActionType("reduce")
+ ActionTypeError = ActionType("error")
+)
+
+type actionEntry int
+
+const actionEntryEmpty = actionEntry(0)
+
+func newShiftActionEntry(state stateNum) actionEntry {
+ return actionEntry(state * -1)
+}
+
+func newReduceActionEntry(prod productionNum) actionEntry {
+ return actionEntry(prod)
+}
+
+func (e actionEntry) isEmpty() bool {
+ return e == actionEntryEmpty
+}
+
+func (e actionEntry) describe() (ActionType, stateNum, productionNum) {
+ if e == actionEntryEmpty {
+ return ActionTypeError, stateNumInitial, productionNumNil
+ }
+ if e < 0 {
+ return ActionTypeShift, stateNum(e * -1), productionNumNil
+ }
+ return ActionTypeReduce, stateNumInitial, productionNum(e)
+}
+
+type GoToType string
+
+const (
+ GoToTypeRegistered = GoToType("registered")
+ GoToTypeError = GoToType("error")
+)
+
+type goToEntry uint
+
+const goToEntryEmpty = goToEntry(0)
+
+func newGoToEntry(state stateNum) goToEntry {
+ return goToEntry(state)
+}
+
+func (e goToEntry) isEmpty() bool {
+ return e == goToEntryEmpty
+}
+
+func (e goToEntry) describe() (GoToType, stateNum) {
+ if e == goToEntryEmpty {
+ return GoToTypeError, stateNumInitial
+ }
+ return GoToTypeRegistered, stateNum(e)
+}
+
+type conflict interface {
+ conflict()
+}
+
+type shiftReduceConflict struct {
+ state stateNum
+ sym symbol
+ nextState stateNum
+ prodNum productionNum
+}
+
+func (c *shiftReduceConflict) conflict() {
+}
+
+type reduceReduceConflict struct {
+ state stateNum
+ sym symbol
+ prodNum1 productionNum
+ prodNum2 productionNum
+}
+
+func (c *reduceReduceConflict) conflict() {
+}
+
+var (
+ _ conflict = &shiftReduceConflict{}
+ _ conflict = &reduceReduceConflict{}
+)
+
+type ParsingTable struct {
+ actionTable []actionEntry
+ goToTable []goToEntry
+ stateCount int
+ terminalCount int
+ nonTerminalCount int
+ expectedTerminals [][]int
+
+ InitialState stateNum
+}
+
+func (t *ParsingTable) getAction(state stateNum, sym symbolNum) (ActionType, stateNum, productionNum) {
+ pos := state.Int()*t.terminalCount + sym.Int()
+ return t.actionTable[pos].describe()
+}
+
+func (t *ParsingTable) getGoTo(state stateNum, sym symbolNum) (GoToType, stateNum) {
+ pos := state.Int()*t.nonTerminalCount + sym.Int()
+ return t.goToTable[pos].describe()
+}
+
+func (t *ParsingTable) readAction(row int, col int) actionEntry {
+ return t.actionTable[row*t.terminalCount+col]
+}
+
+func (t *ParsingTable) writeAction(row int, col int, act actionEntry) {
+ t.actionTable[row*t.terminalCount+col] = act
+}
+
+func (t *ParsingTable) writeGoTo(state stateNum, sym symbol, nextState stateNum) {
+ pos := state.Int()*t.nonTerminalCount + sym.num().Int()
+ t.goToTable[pos] = newGoToEntry(nextState)
+}
+
+type lrTableBuilder struct {
+ automaton *lr0Automaton
+ prods *productionSet
+ termCount int
+ nonTermCount int
+ symTab *symbolTable
+ sym2AnonPat map[symbol]string
+
+ conflicts []conflict
+}
+
+func (b *lrTableBuilder) build() (*ParsingTable, error) {
+ var ptab *ParsingTable
+ {
+ initialState := b.automaton.states[b.automaton.initialState]
+ ptab = &ParsingTable{
+ actionTable: make([]actionEntry, len(b.automaton.states)*b.termCount),
+ goToTable: make([]goToEntry, len(b.automaton.states)*b.nonTermCount),
+ stateCount: len(b.automaton.states),
+ terminalCount: b.termCount,
+ nonTerminalCount: b.nonTermCount,
+ expectedTerminals: make([][]int, len(b.automaton.states)),
+ InitialState: initialState.num,
+ }
+ }
+
+ for _, state := range b.automaton.states {
+ var eTerms []int
+
+ for sym, kID := range state.next {
+ nextState := b.automaton.states[kID]
+ if sym.isTerminal() {
+ eTerms = append(eTerms, sym.num().Int())
+ b.writeShiftAction(ptab, state.num, sym, nextState.num)
+ } else {
+ ptab.writeGoTo(state.num, sym, nextState.num)
+ }
+ }
+
+ for prodID := range state.reducible {
+ reducibleProd, ok := b.prods.findByID(prodID)
+ if !ok {
+ return nil, fmt.Errorf("reducible production not found: %v", prodID)
+ }
+
+ var reducibleItem *lrItem
+ for _, item := range state.items {
+ if item.prod != reducibleProd.id {
+ continue
+ }
+
+ reducibleItem = item
+ break
+ }
+ if reducibleItem == nil {
+ for _, item := range state.emptyProdItems {
+ if item.prod != reducibleProd.id {
+ continue
+ }
+
+ reducibleItem = item
+ break
+ }
+ if reducibleItem == nil {
+ return nil, fmt.Errorf("reducible item not found; state: %v, production: %v", state.num, reducibleProd.num)
+ }
+ }
+
+ for a := range reducibleItem.lookAhead.symbols {
+ eTerms = append(eTerms, a.num().Int())
+ b.writeReduceAction(ptab, state.num, a, reducibleProd.num)
+ }
+ }
+
+ ptab.expectedTerminals[state.num] = eTerms
+ }
+
+ return ptab, nil
+}
+
+// writeShiftAction writes a shift action to the parsing table. When a shift/reduce conflict occurred,
+// we prioritize the shift action.
+func (b *lrTableBuilder) writeShiftAction(tab *ParsingTable, state stateNum, sym symbol, nextState stateNum) {
+ act := tab.readAction(state.Int(), sym.num().Int())
+ if !act.isEmpty() {
+ ty, _, p := act.describe()
+ if ty == ActionTypeReduce {
+ b.conflicts = append(b.conflicts, &shiftReduceConflict{
+ state: state,
+ sym: sym,
+ nextState: nextState,
+ prodNum: p,
+ })
+ }
+ }
+
+ tab.writeAction(state.Int(), sym.num().Int(), newShiftActionEntry(nextState))
+}
+
+// writeReduceAction writes a reduce action to the parsing table. When a shift/reduce conflict occurred,
+// we prioritize the shift action, and when a reduce/reduce conflict we prioritize the action that reduces
+// teh production with higher priority. Productions defined earlier in the grammar file have a higher priority.
+func (b *lrTableBuilder) writeReduceAction(tab *ParsingTable, state stateNum, sym symbol, prod productionNum) {
+ act := tab.readAction(state.Int(), sym.num().Int())
+ if !act.isEmpty() {
+ ty, s, p := act.describe()
+ switch ty {
+ case ActionTypeReduce:
+ if p == prod {
+ return
+ }
+
+ b.conflicts = append(b.conflicts, &reduceReduceConflict{
+ state: state,
+ sym: sym,
+ prodNum1: p,
+ prodNum2: prod,
+ })
+
+ if p < prod {
+ tab.writeAction(state.Int(), sym.num().Int(), newReduceActionEntry(p))
+ } else {
+ tab.writeAction(state.Int(), sym.num().Int(), newReduceActionEntry(prod))
+ }
+ case ActionTypeShift:
+ b.conflicts = append(b.conflicts, &shiftReduceConflict{
+ state: state,
+ sym: sym,
+ nextState: s,
+ prodNum: prod,
+ })
+
+ tab.writeAction(state.Int(), sym.num().Int(), newShiftActionEntry(s))
+ }
+
+ return
+ }
+
+ tab.writeAction(state.Int(), sym.num().Int(), newReduceActionEntry(prod))
+}
+
+func (b *lrTableBuilder) writeDescription(w io.Writer, tab *ParsingTable) {
+ conflicts := map[stateNum][]conflict{}
+ for _, con := range b.conflicts {
+ switch c := con.(type) {
+ case *shiftReduceConflict:
+ conflicts[c.state] = append(conflicts[c.state], c)
+ case *reduceReduceConflict:
+ conflicts[c.state] = append(conflicts[c.state], c)
+ }
+ }
+
+ fmt.Fprintf(w, "# Conflicts\n\n")
+
+ if len(b.conflicts) > 0 {
+ fmt.Fprintf(w, "%v conflics:\n\n", len(b.conflicts))
+
+ for _, conflict := range b.conflicts {
+ switch c := conflict.(type) {
+ case *shiftReduceConflict:
+ fmt.Fprintf(w, "%v: shift/reduce conflict (shift %v, reduce %v) on %v\n", c.state, c.nextState, c.prodNum, b.symbolToText(c.sym))
+ case *reduceReduceConflict:
+ fmt.Fprintf(w, "%v: reduce/reduce conflict (reduce %v and %v) on %v\n", c.state, c.prodNum1, c.prodNum2, b.symbolToText(c.sym))
+ }
+ }
+ fmt.Fprintf(w, "\n")
+ } else {
+ fmt.Fprintf(w, "no conflicts\n\n")
+ }
+
+ fmt.Fprintf(w, "# Terminals\n\n")
+
+ termSyms := b.symTab.terminalSymbols()
+
+ fmt.Fprintf(w, "%v symbols:\n\n", len(termSyms))
+
+ for _, sym := range termSyms {
+ text, ok := b.symTab.toText(sym)
+ if !ok {
+ text = fmt.Sprintf("<symbol not found: %v>", sym)
+ }
+ if strings.HasPrefix(text, "_") {
+ fmt.Fprintf(w, "%4v %v: \"%v\"\n", sym.num(), text, b.sym2AnonPat[sym])
+ } else {
+ fmt.Fprintf(w, "%4v %v\n", sym.num(), text)
+ }
+ }
+
+ fmt.Fprintf(w, "\n")
+
+ fmt.Fprintf(w, "# Productions\n\n")
+
+ fmt.Fprintf(w, "%v productions:\n\n", len(b.prods.getAllProductions()))
+
+ for _, prod := range b.prods.getAllProductions() {
+ fmt.Fprintf(w, "%4v %v\n", prod.num, b.productionToString(prod, -1))
+ }
+
+ fmt.Fprintf(w, "\n# States\n\n")
+
+ fmt.Fprintf(w, "%v states:\n\n", len(b.automaton.states))
+
+ for _, state := range b.automaton.states {
+ fmt.Fprintf(w, "state %v\n", state.num)
+ for _, item := range state.items {
+ prod, ok := b.prods.findByID(item.prod)
+ if !ok {
+ fmt.Fprintf(w, "<production not found>\n")
+ continue
+ }
+ fmt.Fprintf(w, " %v\n", b.productionToString(prod, item.dot))
+ }
+
+ fmt.Fprintf(w, "\n")
+
+ var shiftRecs []string
+ var reduceRecs []string
+ var gotoRecs []string
+ var accRec string
+ {
+ for sym, kID := range state.next {
+ nextState := b.automaton.states[kID]
+ if sym.isTerminal() {
+ shiftRecs = append(shiftRecs, fmt.Sprintf("shift %4v on %v", nextState.num, b.symbolToText(sym)))
+ } else {
+ gotoRecs = append(gotoRecs, fmt.Sprintf("goto %4v on %v", nextState.num, b.symbolToText(sym)))
+ }
+ }
+
+ for prodID := range state.reducible {
+ prod, ok := b.prods.findByID(prodID)
+ if !ok {
+ reduceRecs = append(reduceRecs, "<production not found>")
+ continue
+ }
+ if prod.lhs.isStart() {
+ accRec = "accept on <EOF>"
+ continue
+ }
+
+ var reducibleItem *lrItem
+ for _, item := range state.items {
+ if item.prod != prodID {
+ continue
+ }
+
+ reducibleItem = item
+ break
+ }
+ if reducibleItem == nil {
+ for _, item := range state.emptyProdItems {
+ if item.prod != prodID {
+ continue
+ }
+
+ reducibleItem = item
+ break
+ }
+ if reducibleItem == nil {
+ reduceRecs = append(reduceRecs, "<item not found>")
+ continue
+ }
+ }
+ for a := range reducibleItem.lookAhead.symbols {
+ reduceRecs = append(reduceRecs, fmt.Sprintf("reduce %4v on %v", prod.num, b.symbolToText(a)))
+ }
+ }
+ }
+
+ if len(shiftRecs) > 0 || len(reduceRecs) > 0 {
+ for _, rec := range shiftRecs {
+ fmt.Fprintf(w, " %v\n", rec)
+ }
+ for _, rec := range reduceRecs {
+ fmt.Fprintf(w, " %v\n", rec)
+ }
+ fmt.Fprintf(w, "\n")
+ }
+ if len(gotoRecs) > 0 {
+ for _, rec := range gotoRecs {
+ fmt.Fprintf(w, " %v\n", rec)
+ }
+ fmt.Fprintf(w, "\n")
+ }
+ if accRec != "" {
+ fmt.Fprintf(w, " %v\n\n", accRec)
+ }
+
+ cons, ok := conflicts[state.num]
+ if ok {
+ syms := map[symbol]struct{}{}
+ for _, con := range cons {
+ switch c := con.(type) {
+ case *shiftReduceConflict:
+ fmt.Fprintf(w, " shift/reduce conflict (shift %v, reduce %v) on %v\n", c.nextState, c.prodNum, b.symbolToText(c.sym))
+ syms[c.sym] = struct{}{}
+ case *reduceReduceConflict:
+ fmt.Fprintf(w, " reduce/reduce conflict (reduce %v and %v) on %v\n", c.prodNum1, c.prodNum2, b.symbolToText(c.sym))
+ syms[c.sym] = struct{}{}
+ }
+ }
+ for sym := range syms {
+ ty, s, p := tab.getAction(state.num, sym.num())
+ switch ty {
+ case ActionTypeShift:
+ fmt.Fprintf(w, " adopted shift %4v on %v\n", s, b.symbolToText(sym))
+ case ActionTypeReduce:
+ fmt.Fprintf(w, " adopted reduce %4v on %v\n", p, b.symbolToText(sym))
+ }
+ }
+ fmt.Fprintf(w, "\n")
+ }
+ }
+}
+
+func (b *lrTableBuilder) productionToString(prod *production, dot int) string {
+ var w strings.Builder
+ fmt.Fprintf(&w, "%v →", b.symbolToText(prod.lhs))
+ for n, rhs := range prod.rhs {
+ if n == dot {
+ fmt.Fprintf(&w, " ・")
+ }
+ fmt.Fprintf(&w, " %v", b.symbolToText(rhs))
+ }
+ if dot == len(prod.rhs) {
+ fmt.Fprintf(&w, " ・")
+ }
+
+ return w.String()
+}
+
+func (b *lrTableBuilder) symbolToText(sym symbol) string {
+ if sym.isNil() {
+ return "<NULL>"
+ }
+ if sym.isEOF() {
+ return "<EOF>"
+ }
+
+ text, ok := b.symTab.toText(sym)
+ if !ok {
+ return fmt.Sprintf("<symbol not found: %v>", sym)
+ }
+
+ if strings.HasPrefix(text, "_") {
+ pat, ok := b.sym2AnonPat[sym]
+ if !ok {
+ return fmt.Sprintf("<pattern not found: %v>", text)
+ }
+
+ return fmt.Sprintf(`"%v"`, pat)
+ }
+
+ return text
+}
generated by cgit v1.2.3 (git 2.49.0) at 2025-07-12 22:37:35 +0000