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package parser
import (
"log"
"strconv"
"github.com/mvertes/parscan/lang"
"github.com/mvertes/parscan/scanner"
"github.com/mvertes/parscan/symbol"
"github.com/mvertes/parscan/vm"
)
// parseExpr transform an infix expression into a postfix notation.
func (p *Parser) parseExpr(in Tokens, typeStr string) (out Tokens, err error) {
log.Println("parseExpr in:", in)
var ops Tokens
popop := func() (t scanner.Token) {
l := len(ops) - 1
t = ops[l]
ops = ops[:l]
if t.Tok.IsLogicalOp() {
t.Tok = lang.Label // Implement conditional branching directly.
}
return t
}
lin := len(in)
for i := 0; i < lin; i++ {
switch t := in[i]; t.Tok {
case lang.Int, lang.String:
out = append(out, t)
case lang.Func:
// Function as value (i.e closure).
if out, err = p.parseFunc(in); err != nil {
return out, err
}
// Get function label and use it as a symbol ident.
fid := out[1]
fid.Tok = lang.Ident
out = append(out, fid)
return out, err
case lang.Period:
// TODO: fail if next is not an ident.
t.Str += in[i+1].Str // Hardwire selector argument.
for len(ops) > 0 && p.precedence(t) < p.precedence(ops[len(ops)-1]) {
out = append(out, popop())
}
ops = append(ops, t)
i++ // Skip over next ident.
case lang.Colon:
t.Str = typeStr
for len(ops) > 0 && p.precedence(t) < p.precedence(ops[len(ops)-1]) {
out = append(out, popop())
}
ops = append(ops, t)
case lang.Add, lang.And, lang.Assign, lang.Define, lang.Equal, lang.Greater, lang.Less, lang.Mul, lang.Not, lang.Sub, lang.Shl, lang.Shr:
if i == 0 || in[i-1].Tok.IsOperator() {
// An operator preceded by an operator or no token is unary.
t.Tok = lang.UnaryOp[t.Tok]
}
for len(ops) > 0 && p.precedence(t) < p.precedence(ops[len(ops)-1]) {
out = append(out, popop())
}
ops = append(ops, t)
case lang.Land:
for len(ops) > 0 && p.precedence(t) < p.precedence(ops[len(ops)-1]) {
out = append(out, popop())
}
xp := strconv.Itoa(p.labelCount[p.scope])
p.labelCount[p.scope]++
out = append(out, scanner.Token{Tok: lang.JumpSetFalse, Str: p.scope + "x" + xp})
t.Str = p.scope + "x" + xp
ops = append(ops, t)
case lang.Lor:
for len(ops) > 0 && p.precedence(t) < p.precedence(ops[len(ops)-1]) {
out = append(out, popop())
}
xp := strconv.Itoa(p.labelCount[p.scope])
p.labelCount[p.scope]++
out = append(out, scanner.Token{Tok: lang.JumpSetTrue, Str: p.scope + "x" + xp})
t.Str = p.scope + "x" + xp
ops = append(ops, t)
case lang.Ident:
s, sc, ok := p.Symbols.Get(t.Str, p.scope)
if ok && sc != "" {
t.Str = sc + "/" + t.Str
}
if s != nil && s.Kind == symbol.Type {
typeStr = s.Type.String()
}
out = append(out, t)
if i+1 < len(in) && in[i+1].Tok == lang.Define {
// Ident is to be assigned next. Define it as a var.
p.Symbols.Add(symbol.UnsetAddr, t.Str, vm.Value{}, symbol.Var, nil, false)
}
case lang.ParenBlock:
toks, err := p.parseExprStr(t.Block(), typeStr)
if err != nil {
return out, err
}
if i == 0 || in[i-1].Tok.IsOperator() {
out = append(out, toks...)
} else {
prec := p.precedence(scanner.Token{Tok: lang.Call})
for len(ops) > 0 && prec < p.precedence(ops[len(ops)-1]) {
out = append(out, popop())
}
// func call: ensure that the func token in on the top of the stack, after args.
ops = append(ops, scanner.Token{Tok: lang.Call, Pos: t.Pos, Beg: p.numItems(t.Block(), lang.Comma)})
out = append(out, toks...)
}
case lang.BraceBlock:
toks, err := p.parseComposite(t.Block(), typeStr)
out = append(out, toks...)
if err != nil {
return out, err
}
ops = append(ops, scanner.Token{Tok: lang.Composite, Pos: t.Pos, Str: typeStr})
case lang.BracketBlock:
if i == 0 || in[i-1].Tok.IsOperator() {
// array or slice type expression
typ, err := p.parseTypeExpr(in[i:])
if err != nil {
return out, err
}
typeStr = typ.String()
p.Symbols.Add(symbol.UnsetAddr, typ.String(), vm.NewValue(typ), symbol.Type, typ, p.funcScope != "")
out = append(out, scanner.Token{Tok: lang.Ident, Pos: t.Pos, Str: typeStr})
i++
break
}
toks, err := p.parseExprStr(t.Block(), typeStr)
if err != nil {
return out, err
}
out = append(out, toks...)
ops = append(ops, scanner.Token{Tok: lang.Index, Pos: t.Pos})
case lang.Struct:
typ, err := p.parseTypeExpr(in[i : i+2])
if err != nil {
return out, err
}
typeStr = typ.String()
p.Symbols.Add(symbol.UnsetAddr, typ.String(), vm.NewValue(typ), symbol.Type, typ, p.funcScope != "")
out = append(out, scanner.Token{Tok: lang.Ident, Pos: t.Pos, Str: typeStr})
i++ // FIXME: number of tokens to skip should be computed from type parsing.
case lang.Map:
typ, err := p.parseTypeExpr(in[i:])
if err != nil {
return out, err
}
typeStr = typ.String()
p.Symbols.Add(symbol.UnsetAddr, typ.String(), vm.NewValue(typ), symbol.Type, typ, p.funcScope != "")
out = append(out, scanner.Token{Tok: lang.Ident, Pos: t.Pos, Str: typeStr})
i += 2 // FIXME: number of tokens to skip should be computed from type parsing.
case lang.Comment:
default:
log.Println("unexpected token:", t)
}
}
for len(ops) > 0 {
out = append(out, popop())
}
log.Println("Final out:", out)
return out, err
}
func (p *Parser) parseComposite(s, typ string) (Tokens, error) {
tokens, err := p.Scan(s, false)
if err != nil {
return nil, err
}
noColon := len(tokens) > 0 && tokens.Index(lang.Colon) == -1
var result Tokens
var sliceLen int
for i, sub := range tokens.Split(lang.Comma) {
toks, err := p.parseExpr(sub, typ)
if err != nil {
return result, err
}
if noColon {
// Insert a numeric index key and a colon operator.
result = append(result, scanner.Token{Tok: lang.Int, Str: strconv.Itoa(i)})
result = append(result, toks...)
result = append(result, scanner.Token{Tok: lang.Colon, Str: ":"})
sliceLen++
} else {
result = append(result, toks...)
}
}
p.Symbols[typ].SliceLen = sliceLen
return result, nil
}
func (p *Parser) parseExprStr(s, typ string) (tokens Tokens, err error) {
if tokens, err = p.Scan(s, false); err != nil {
return tokens, err
}
var result Tokens
for _, sub := range tokens.Split(lang.Comma) {
toks, err := p.parseExpr(sub, typ)
if err != nil {
return result, err
}
result = append(toks, result...)
}
return result, err
}
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