diff options
Diffstat (limited to 'grammar/grammar.go')
| -rw-r--r-- | grammar/grammar.go | 84 |
1 files changed, 79 insertions, 5 deletions
diff --git a/grammar/grammar.go b/grammar/grammar.go index 7479683..05ba836 100644 --- a/grammar/grammar.go +++ b/grammar/grammar.go @@ -8,12 +8,18 @@ import ( "github.com/nihei9/vartan/spec" ) +type astActionEntry struct { + position int + expansion bool +} + type Grammar struct { lexSpec *mlspec.LexSpec skipLexKinds []mlspec.LexKind productionSet *productionSet augmentedStartSymbol symbol symbolTable *symbolTable + astActions map[productionID][]*astActionEntry } func NewGrammar(root *spec.RootNode) (*Grammar, error) { @@ -54,17 +60,20 @@ func NewGrammar(root *spec.RootNode) (*Grammar, error) { act := alt.Action switch act.Name { case "skip": - if act.Parameter != "" { + param := act.Parameter + if param != nil { return nil, fmt.Errorf("action 'skip' needs no parameter") } skip = append(skip, mlspec.LexKind(prod.LHS)) case "push": - if act.Parameter == "" { - return nil, fmt.Errorf("action 'push' needs a parameter") + param := act.Parameter + if param == nil || param.ID == "" { + return nil, fmt.Errorf("action 'push' needs an ID parameter") } - push = mlspec.LexModeName(act.Parameter) + push = mlspec.LexModeName(param.ID) case "pop": - if act.Parameter != "" { + param := act.Parameter + if param != nil { return nil, fmt.Errorf("action 'pop' needs no parameter") } pop = true @@ -134,6 +143,7 @@ func NewGrammar(root *spec.RootNode) (*Grammar, error) { prods := newProductionSet() var augStartSym symbol + astActs := map[productionID][]*astActionEntry{} { startProd := root.Productions[0] augStartText := fmt.Sprintf("%s'", startProd.LHS) @@ -196,6 +206,51 @@ func NewGrammar(root *spec.RootNode) (*Grammar, error) { return nil, err } prods.append(p) + + if alt.Action != nil { + act := alt.Action + switch act.Name { + case "ast": + param := act.Parameter + if param == nil || param.Tree == nil { + return nil, fmt.Errorf("action 'push' needs a tree parameter") + } + lhsText, ok := symTab.toText(p.lhs) + if !ok || param.Tree.Name != lhsText { + return nil, fmt.Errorf("a name of a tree structure must be the same ID as an LHS of a production; LHS: %v", lhsText) + } + astAct := make([]*astActionEntry, len(param.Tree.Children)) + for i, c := range param.Tree.Children { + if c.Position > len(alt.Elements) { + return nil, fmt.Errorf("a position must be less than or equal to the length of an alternative; alternative length: %v", len(alt.Elements)) + } + + if c.Expansion { + offset := c.Position - 1 + elem := alt.Elements[offset] + if elem.Pattern != "" { + return nil, fmt.Errorf("the expansion symbol cannot be applied to a pattern ($%v: %v)", c.Position, elem.Pattern) + } + elemSym, ok := symTab.toSymbol(elem.ID) + if !ok { + // If the symbol was not found, it's a bug. + return nil, fmt.Errorf("a symbol corresponding to a position ($%v: %v) was not found", c.Position, elem.ID) + } + if elemSym.isTerminal() { + return nil, fmt.Errorf("the expansion symbol cannot be applied to a terminal symbol ($%v: %v)", c.Position, elem.ID) + } + } + + astAct[i] = &astActionEntry{ + position: c.Position, + expansion: c.Expansion, + } + } + astActs[p.id] = astAct + default: + return nil, fmt.Errorf("invalid action name '%v'", act.Name) + } + } } } } @@ -206,6 +261,7 @@ func NewGrammar(root *spec.RootNode) (*Grammar, error) { productionSet: prods, augmentedStartSymbol: augStartSym, symbolTable: symTab, + astActions: astActs, }, nil } @@ -297,9 +353,24 @@ func Compile(gram *Grammar) (*spec.CompiledGrammar, error) { lhsSyms := make([]int, len(gram.productionSet.getAllProductions())+1) altSymCounts := make([]int, len(gram.productionSet.getAllProductions())+1) + astActEnties := make([][]int, len(gram.productionSet.getAllProductions())+1) for _, p := range gram.productionSet.getAllProductions() { lhsSyms[p.num] = p.lhs.num().Int() altSymCounts[p.num] = p.rhsLen + + astAct, ok := gram.astActions[p.id] + if !ok { + continue + } + astActEntry := make([]int, len(astAct)) + for i, e := range astAct { + if e.expansion { + astActEntry[i] = e.position * -1 + } else { + astActEntry[i] = e.position + } + } + astActEnties[p.num] = astActEntry } return &spec.CompiledGrammar{ @@ -325,5 +396,8 @@ func Compile(gram *Grammar) (*spec.CompiledGrammar, error) { NonTerminalCount: tab.nonTerminalCount, EOFSymbol: symbolEOF.num().Int(), }, + ASTAction: &spec.ASTAction{ + Entries: astActEnties, + }, }, nil } |