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package peg
import (
"fmt"
)
type (
// Expressions
Exp interface {
Match(int) (int, *Result)
}
Terminal struct {
*Parser
Character int
}
NonTerminal struct {
*Parser
Name string
Expression Exp
}
Sequence struct {
*Parser
Expressions []Exp
}
OrderedChoice struct {
*Parser
Expressions []Exp
}
ZeroOrMore struct {
*Parser
Expression Exp
}
OneOrMore struct {
*Parser
Expression Exp
}
Optional struct {
*Parser
Expression Exp
}
AndPredicate struct {
*Parser
Expression Exp
}
NotPredicate struct {
*Parser
Expression Exp
}
)
// Terminal
func (this *Terminal) Match(offset int) (int, *Result) {
if offset < len(this.Parser.working) && int(this.Parser.working[offset]) == this.Character {
return offset + 1, this.Parser.pass(offset, 1, this, nil)
}
return offset, this.Parser.fail(offset, 0, this, nil)
}
func (this *Terminal) String() string {
return "<" + string(this.Character) + ">"
}
// Non Terminal
func (this *NonTerminal) Match(offset int) (int, *Result) {
o, r := this.Expression.Match(offset)
if r.Valid {
return o, this.Parser.pass(offset, o-offset, this, []*Result{r})
}
return offset, this.Parser.fail(offset, o, this, []*Result{r})
}
func (this *NonTerminal) String() string {
return "(" + this.Name + ":" + fmt.Sprint(this.Expression) + ")"
}
// Sequence
func (this *Sequence) Match(offset int) (int, *Result) {
o := offset
var r *Result
children := make([]*Result, 0)
for _, exp := range this.Expressions {
o, r = exp.Match(o)
children = append(children, r)
if !r.Valid {
return offset, this.Parser.fail(o, o-offset, this, children)
}
}
return o, this.Parser.pass(offset, o-offset, this, children)
}
func (this *Sequence) String() string {
str := ""
for i, e := range this.Expressions {
if i > 0 {
str += " "
}
str += fmt.Sprint(e)
}
return "(" + str + ")"
}
// Ordered Choice
func (this *OrderedChoice) Match(start int) (int, *Result) {
children := make([]*Result, 0)
for _, exp := range this.Expressions {
i, r := exp.Match(start)
if r.Valid {
return i, this.Parser.pass(i, i-start, this, []*Result{r})
}
children = append(children, r)
}
return start, this.Parser.fail(start, 0, this, children)
}
func (this *OrderedChoice) String() string {
str := ""
for i, e := range this.Expressions {
if i > 0 {
str += " / "
}
str += fmt.Sprint(e)
}
return str
}
// Zero or More
func (this *ZeroOrMore) Match(offset int) (int, *Result) {
o := offset
children := make([]*Result, 0)
for {
i, r := this.Expression.Match(o)
if !r.Valid {
break
}
children = append(children, r)
o = i
}
return o, this.Parser.pass(offset, o-offset, this, children)
}
func (this *ZeroOrMore) String() string {
return "(" + fmt.Sprint(this.Expression) + ")*"
}
// One or More
func (this *OneOrMore) Match(offset int) (int, *Result) {
o := offset
children := make([]*Result, 0)
for {
i, r := this.Expression.Match(o)
if !r.Valid {
if len(children) == 0 {
return offset, this.Parser.fail(i, i-offset, this, []*Result{r})
}
break
}
children = append(children, r)
o = i
}
return o, this.Parser.pass(offset, o-offset, this, children)
}
func (this *OneOrMore) String() string {
return "(" + fmt.Sprint(this.Expression) + ")+"
}
// Optional
func (this *Optional) Match(start int) (int, *Result) {
current, result := this.Expression.Match(start)
if result.Valid {
return current, this.Parser.pass(current, current-start, this, []*Result{result})
}
return start, this.Parser.pass(start, 0, this, nil)
}
func (this *Optional) String() string {
return "(" + fmt.Sprint(this.Expression) + ")?"
}
// And Predicate
func (this *AndPredicate) Match(start int) (int, *Result) {
// Ignore the new position
_, result := this.Expression.Match(start)
if result.Valid {
return start, this.Parser.pass(start, 0, this, []*Result{result})
}
return start, this.Parser.fail(start, 0, this, []*Result{result})
}
func (this *AndPredicate) String() string {
return "&(" + fmt.Sprint(this.Expression) + ")"
}
// Not Predicate
func (this *NotPredicate) Match(start int) (int, *Result) {
// Ignore the new position
_, result := this.Expression.Match(start)
if !result.Valid {
return start, this.Parser.pass(start, 0, this, []*Result{result})
}
return start, this.Parser.fail(start, 0, this, []*Result{result})
}
func (this *NotPredicate) String() string {
return "!(" + fmt.Sprint(this.Expression) + ")"
}
|
