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firstfollow.go
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firstfollow.go
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// Copyright 2019 Marius Ackerman
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package firstfollow
import (
"bytes"
"fmt"
"io"
"os"
"path"
"github.com/goccmack/gogll/ast"
"github.com/goccmack/gogll/cfg"
"github.com/goccmack/gogll/frstflw"
"github.com/goccmack/gogll/goutil/ioutil"
)
func Gen(g *ast.Grammar, ff *frstflw.FF) {
if !cfg.Verbose {
return
}
w := new(bytes.Buffer)
genFirstSets(w, g, ff)
genFollowSets(w, g, ff)
fname := path.Join(cfg.BaseDir, "first_follow.txt")
if err := ioutil.WriteFile(fname, w.Bytes()); err != nil {
fmt.Printf("Error writing first and follow: %s\n", err)
os.Exit(1)
}
}
func genFirstSets(w io.Writer, g *ast.Grammar, ff *frstflw.FF) {
for _, s := range g.GetSymbols() {
genFirstSet(w, s, ff)
}
}
func genFirstSet(w io.Writer, symbol string, ff *frstflw.FF) {
fmt.Fprintf(w, "%s: ", symbol)
for _, s := range ff.FirstOfSymbol(symbol).Elements() {
fmt.Fprintf(w, `%s `, s)
}
fmt.Fprintln(w)
}
func genFollowSets(w io.Writer, g *ast.Grammar, ff *frstflw.FF) {
for _, s := range g.GetNonTerminals() {
genFollowSet(w, s, ff)
}
}
func genFollowSet(w io.Writer, nt string, ff *frstflw.FF) {
fmt.Fprintf(w, "Follow(%s): ", nt)
for _, s := range ff.Follow(nt).Elements() {
fmt.Fprintf(w, `%s `, s)
}
fmt.Fprintln(w)
}