// setConst sets x to the untyped constant for literal lit.
func (x *operand) setConst(tok token.Token, lit string) {
val := exact.MakeFromLiteral(lit, tok)
if val == nil {
// TODO(gri) Should we make it an unknown constant instead?
x.mode = invalid
return
}
var kind BasicKind
switch tok {
case token.INT:
kind = UntypedInt
case token.FLOAT:
kind = UntypedFloat
case token.IMAG:
kind = UntypedComplex
case token.CHAR:
kind = UntypedRune
case token.STRING:
kind = UntypedString
}
x.mode = constant
x.typ = Typ[kind]
x.val = val
}
// number = int_lit [ "p" int_lit ] .
//
func (p *parser) parseNumber() (typ *types.Basic, val exact.Value) {
// mantissa
mant := exact.MakeFromLiteral(p.parseInt(), token.INT)
if mant == nil {
panic("invalid mantissa")
}
if p.lit == "p" {
// exponent (base 2)
p.next()
exp, err := strconv.ParseInt(p.parseInt(), 10, 0)
if err != nil {
p.error(err)
}
if exp < 0 {
denom := exact.MakeInt64(1)
denom = exact.Shift(denom, token.SHL, uint(-exp))
typ = types.Typ[types.UntypedFloat]
val = exact.BinaryOp(mant, token.QUO, denom)
return
}
if exp > 0 {
mant = exact.Shift(mant, token.SHL, uint(exp))
}
typ = types.Typ[types.UntypedFloat]
val = mant
return
}
typ = types.Typ[types.UntypedInt]
val = mant
return
}
// ConstDecl = "const" ExportedName [ Type ] "=" Literal .
// Literal = bool_lit | int_lit | float_lit | complex_lit | rune_lit | string_lit .
// bool_lit = "true" | "false" .
// complex_lit = "(" float_lit "+" float_lit "i" ")" .
// rune_lit = "(" int_lit "+" int_lit ")" .
// string_lit = `"` { unicode_char } `"` .
//
func (p *parser) parseConstDecl() {
p.expectKeyword("const")
pkg, name := p.parseExportedName()
var typ0 types.Type
if p.tok != '=' {
typ0 = p.parseType()
}
p.expect('=')
var typ types.Type
var val exact.Value
switch p.tok {
case scanner.Ident:
// bool_lit
if p.lit != "true" && p.lit != "false" {
p.error("expected true or false")
}
typ = types.Typ[types.UntypedBool]
val = exact.MakeBool(p.lit == "true")
p.next()
case '-', scanner.Int:
// int_lit
typ, val = p.parseNumber()
case '(':
// complex_lit or rune_lit
p.next()
if p.tok == scanner.Char {
p.next()
p.expect('+')
typ = types.Typ[types.UntypedRune]
_, val = p.parseNumber()
p.expect(')')
break
}
_, re := p.parseNumber()
p.expect('+')
_, im := p.parseNumber()
p.expectKeyword("i")
p.expect(')')
typ = types.Typ[types.UntypedComplex]
val = exact.BinaryOp(re, token.ADD, exact.MakeImag(im))
case scanner.Char:
// rune_lit
typ = types.Typ[types.UntypedRune]
val = exact.MakeFromLiteral(p.lit, token.CHAR)
p.next()
case scanner.String:
// string_lit
typ = types.Typ[types.UntypedString]
val = exact.MakeFromLiteral(p.lit, token.STRING)
p.next()
default:
p.errorf("expected literal got %s", scanner.TokenString(p.tok))
}
if typ0 == nil {
typ0 = typ
}
pkg.Scope().Insert(types.NewConst(token.NoPos, pkg, name, typ0, val))
}
// ConstValue = string | "false" | "true" | ["-"] (int ["'"] | FloatOrComplex) .
// FloatOrComplex = float ["i" | ("+"|"-") float "i"] .
func (p *parser) parseConstValue() (val exact.Value, typ types.Type) {
switch p.tok {
case scanner.String:
str := p.parseString()
val = exact.MakeString(str)
typ = types.Typ[types.UntypedString]
return
case scanner.Ident:
b := false
switch p.lit {
case "false":
case "true":
b = true
default:
p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
}
p.next()
val = exact.MakeBool(b)
typ = types.Typ[types.UntypedBool]
return
}
sign := ""
if p.tok == '-' {
p.next()
sign = "-"
}
switch p.tok {
case scanner.Int:
val = exact.MakeFromLiteral(sign+p.lit, token.INT)
if val == nil {
p.error("could not parse integer literal")
}
p.next()
if p.tok == '\'' {
p.next()
typ = types.Typ[types.UntypedRune]
} else {
typ = types.Typ[types.UntypedInt]
}
case scanner.Float:
re := sign + p.lit
p.next()
var im string
switch p.tok {
case '+':
p.next()
im = p.expect(scanner.Float)
case '-':
p.next()
im = "-" + p.expect(scanner.Float)
case scanner.Ident:
// re is in fact the imaginary component. Expect "i" below.
im = re
re = "0"
default:
val = exact.MakeFromLiteral(re, token.FLOAT)
if val == nil {
p.error("could not parse float literal")
}
typ = types.Typ[types.UntypedFloat]
return
}
p.expectKeyword("i")
reval := exact.MakeFromLiteral(re, token.FLOAT)
if reval == nil {
p.error("could not parse real component of complex literal")
}
imval := exact.MakeFromLiteral(im+"i", token.IMAG)
if imval == nil {
p.error("could not parse imag component of complex literal")
}
val = exact.BinaryOp(reval, token.ADD, imval)
typ = types.Typ[types.UntypedComplex]
default:
p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
}
return
}