nswrap/types/combinators.go

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package types
import (
//"fmt"
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"regexp"
)
var (
whitespace *regexp.Regexp
wordchars *regexp.Regexp
reservedwords *regexp.Regexp
)
func init() {
whitespace = regexp.MustCompile(" *")
wordchars = regexp.MustCompile(`[_0-9a-zA-Z]`)
reservedwords = regexp.MustCompile("^(void|char|short|int|long|float|double|signed|unsigned|_Bool|_Complex|const|restrict|volatile|struct|union|enum)$")
}
type Parser func(string, *Node) (string, *Node)
// Adders
//Child takes a parser and adds its output node (if non-nil) to the tree.
//FIXME -- broken?
func Child(p Parser) Parser {
return func(s string, n *Node) (string, *Node) {
dbg("Child(%s %p)\n",n.Kind,n)
s2,n2 := p(s,n)
if n2 == nil {
return s,nil
}
if n2 != n {
dbg("Child(%p): AddChild()\n",p)
n.AddChild(n2)
}
return s2,n
}
}
//ChildOf takes a node and adds results of a parser to it as a child
func ChildOf(ret *Node, p Parser) Parser {
return func(s string, n *Node) (string, *Node) {
dbg("ChildOf(%s %p) %s %p\n",ret.Kind,ret,n.Kind,n)
s2,n2 := p(s,ret)
if n2 == nil {
return s,nil
}
if n2 == ret {
dbg("ChildOf(ret = %p) n2 = %p. WHAT\n",ret,n2)
ret.Children = n2.Children
} else {
dbg("ChildOf(ret = %p) AddChild()\n",ret)
ret.AddChild(n2)
}
return s2,ret
}
}
//Children takes a parser returns a parser that adds the children of its
//output node to the tree. If multiple parsers are passed in, they are
//passed to Seq(...)
func Children(ps ...Parser) Parser {
if len(ps) > 1 {
return Children(Seq(ps...))
}
p := ps[0]
return func(s string, n *Node) (string, *Node) {
dbg("Children(%s %p)\n",n.Kind,n)
s2,n2 := p(s,n)
if n2 == nil {
return s,nil
}
for _,c := range n2.Children {
dbg("Children(%s %p) AddChild() from %p\n",n.Kind,n,n2)
if c != n {
n.AddChild(c)
}
}
return s2,n
}
}
//ChildrenOf takes a node and adds the children of a parser's output node
//to it as its children.
func ChildrenOf(ret *Node, p Parser) Parser {
return func(s string, n *Node) (string, *Node) {
dbg("ChildrenOf(%s %p) %s %p\n",ret.Kind,ret,n.Kind,n)
return Children(p)(s,ret)
}
}
func NodeNamed(k string, p Parser) Parser {
return func(s string, n *Node) (string, *Node) {
s2,n2 := p(s,n)
if n2 != nil {
n2.Kind = k
}
return s2,n2
}
}
// Combinators
//Opt optionally runs a Parser, returning the input node if it fails
func Opt(p Parser) Parser {
return func(s string, n *Node) (string, *Node) {
s2,n2 := p(s,n)
if n2 == nil {
return s,n
}
return s2,n2
}
}
//OneOf picks the first matching parser and returns its result
func OneOf(ps ...Parser) Parser {
dbg("OneOf(%p)\n",ps)
return func(s string, n *Node) (string, *Node) {
for _,p := range ps {
s2,n2 := p(s,n)
if n2 != nil {
return s2,n2
}
}
return s,nil
}
}
//Doesn't work? May have side effects that do not get unwound.
func Longest(ps ...Parser) Parser {
dbg("Longest(%p)\n",ps)
return func(s string, n *Node) (string, *Node) {
ss := make([]string,len(ps))
ns := make([]*Node,len(ps))
//An arbitrarily large number so I don't have to import "math"
minrem := 10000
mini := 0
for i,p := range ps {
ss[i],ns[i] = p(s,n)
if ns[i] != nil && len(ss[i]) < minrem {
minrem = len(ss[i])
mini = i
}
}
if minrem < 10000 {
return ss[mini],ns[mini]
}
return s,nil
}
}
//Seq applies parsers in sequence, adding results as children to the input
//node. Returns nil and the input string unless the entire sequence succeeds
func Seq(ps ...Parser) Parser {
dbg("Seq(%p)\n",ps)
p := func(s string, n *Node) (string, *Node) {
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ret := NewNode("Seq")
s2, n2 := s,n
for _,p := range ps {
s2, n2 = p(s2,ret)
if n2 == nil {
return s,nil
}
if n2 != ret {
dbg("Seq(%p): AddChild()\n",ps)
ret.AddChild(n2)
}
}
return s2,ret
}
return Children(p)
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}
//Like Seq but subsequent children are nested inside their earlier siblings.
func Nest(ps ...Parser) Parser {
dbg("Nest(%p)\n",ps)
p := func(s string, n *Node) (string, *Node) {
ret := NewNode("Nest")
s2,n2 := Seq(ps...)(s,ret)
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if n2 == nil {
return s,nil
}
ocs := n2.Children
ret.Children = []*Node{}
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n3 := ret
for _,c := range ocs {
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n3.AddChild(c)
n3 = c
}
return s2,ret
}
return Children(p)
}
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//ZeroOrMore returns a sequence of zero or more nodes
func ZeroOrMore(p Parser) Parser {
ret := func(s string, n *Node) (string, *Node) {
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ret := NewNode("ZeroOrMore")
dbg("ZeroOrMore(%s %p) ret = %p\n",n.Kind,n,ret)
var s2 string
var n2 *Node
for s2,n2 = p(s,n); n2 != nil; s2,n2 = p(s2,n) {
dbg("ZeroOrMore(%p): AddChild()\n",p)
ret.AddChild(n2)
}
if len(ret.Children) > 0 {
return s2,ret
}
return s,n
}
return Children(ret)
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}
func OneOrMore(p Parser) Parser {
return Seq(p,ZeroOrMore(p))
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}
func Parenthesized(p Parser) Parser {
return Children(Seq(Lit("("),p,Lit(")")))
}
func Bracketed(p Parser) Parser {
return Seq(Lit("["),p,Lit("]"))
}
func AngBracketed(p Parser) Parser {
return Children(Seq(Lit("<"),p,Lit(">")))
}
func CurlyBracketed(p Parser) Parser {
return Children(Seq(Lit("{"),p,Lit("}")))
}
// Recognizers
func Word(f string) Parser {
return Lit(f,true)
}
func Lit(f string, ws ...bool) Parser {
word := false
if len(ws) > 0 {
word = ws[0]
}
lenf := len(f)
return func(s string, n *Node) (string, *Node) {
ret := NewNode("Lit",f)
dbg("Lit(%p) %s ret = %p\n",n,f,ret)
if len(s) < lenf {
return s,nil
}
if f == s[:lenf] && !(word && len(s) > lenf && wordchars.Match([]byte{s[lenf]})) {
adv := lenf
if loc := whitespace.FindStringIndex(s[lenf:]); loc != nil {
adv += loc[1]
}
return s[adv:],ret
}
return s,nil
}
}
func Regexp(f string) Parser {
f = "^" + f
r := regexp.MustCompile(f)
return func(s string, n *Node) (string, *Node) {
dbg("Regexp(%p) %s\n",n,f)
if loc := r.FindStringIndex(s); loc != nil {
lenf := loc[1]
adv := lenf
if loc := whitespace.FindStringIndex(s[lenf:]); loc != nil {
adv += loc[1]
}
ret := NewNode("Regexp",s[:lenf])
dbg("Regexp(%p): ret = %p (%s)\n",n,ret,s[:lenf])
return s[adv:],ret
}
return s,nil
}
}