diff options
Diffstat (limited to 'grammar/parsing_table.go')
| -rw-r--r-- | grammar/parsing_table.go | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/grammar/parsing_table.go b/grammar/parsing_table.go index 903f95a..aee5963 100644 --- a/grammar/parsing_table.go +++ b/grammar/parsing_table.go @@ -136,6 +136,7 @@ type lrTableBuilder struct { nonTermCount int symTab *symbolTable sym2AnonPat map[symbol]string + precAndAssoc *precAndAssoc conflicts []conflict } @@ -222,6 +223,12 @@ func (b *lrTableBuilder) writeShiftAction(tab *ParsingTable, state stateNum, sym nextState: nextState, prodNum: p, }) + + if b.resolveConflict(sym.num(), p) == ActionTypeShift { + tab.writeAction(state.Int(), sym.num().Int(), newShiftActionEntry(nextState)) + } + + return } } @@ -230,7 +237,7 @@ func (b *lrTableBuilder) writeShiftAction(tab *ParsingTable, state stateNum, sym // 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. +// the 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() { @@ -261,7 +268,9 @@ func (b *lrTableBuilder) writeReduceAction(tab *ParsingTable, state stateNum, sy prodNum: prod, }) - tab.writeAction(state.Int(), sym.num().Int(), newShiftActionEntry(s)) + if b.resolveConflict(sym.num(), prod) == ActionTypeReduce { + tab.writeAction(state.Int(), sym.num().Int(), newReduceActionEntry(prod)) + } } return @@ -270,6 +279,22 @@ func (b *lrTableBuilder) writeReduceAction(tab *ParsingTable, state stateNum, sy tab.writeAction(state.Int(), sym.num().Int(), newReduceActionEntry(prod)) } +func (b *lrTableBuilder) resolveConflict(sym symbolNum, prod productionNum) ActionType { + symPrec := b.precAndAssoc.terminalPrecedence(sym) + prodPrec := b.precAndAssoc.productionPredence(prod) + if symPrec < prodPrec { + return ActionTypeShift + } + if symPrec == prodPrec { + assoc := b.precAndAssoc.productionAssociativity(prod) + if assoc != assocTypeLeft { + return ActionTypeShift + } + } + + return ActionTypeReduce +} + func (b *lrTableBuilder) writeDescription(w io.Writer, tab *ParsingTable) { conflicts := map[stateNum][]conflict{} for _, con := range b.conflicts { |