// atom_number/2 as defined in SWI-Prolog
func BuiltinAtomNumber2(m Machine, args []term.Term) (ret ForeignReturn) {
number := args[1]
if !term.IsVariable(args[0]) {
atom := args[0].(term.Callable)
defer func() { // convert parsing panics into fail
if x := recover(); x != nil {
ret = ForeignFail()
}
}()
if strings.Contains(atom.Name(), ".") {
number = term.NewFloat(atom.Name())
} else {
number = term.NewInt(atom.Name())
}
return ForeignUnify(args[1], number)
} else if !term.IsVariable(number) {
atom := term.NewAtom(number.String())
return ForeignUnify(args[0], atom)
}
msg := fmt.Sprintf("atom_number/2: Arguments are not sufficiently instantiated: %s and %s", args[0], args[1])
panic(msg)
}
// parse a single term
func (r *TermReader) term(p priority, i *lex.List, o **lex.List, t *term.Term) bool {
var op, f string
var t0, t1 term.Term
var opP, argP priority
// fmt.Printf("seeking term with %s\n", i.Value.Content)
// prefix operator
if r.prefix(&op, &opP, &argP, i, o) && opP <= p && r.term(argP, *o, o, &t0) {
opT := term.NewCallable(op, t0)
return r.restTerm(opP, p, *o, o, opT, t)
}
// list notation for compound terms §6.3.5
if r.tok('[', i, o) && r.term(999, *o, o, &t0) && r.listItems(*o, o, &t1) {
list := term.NewCallable(".", t0, t1)
return r.restTerm(0, p, *o, o, list, t)
}
if r.tok('[', i, o) && r.tok(']', *o, o) {
list := term.NewAtom("[]")
return r.restTerm(0, p, *o, o, list, t)
}
// parenthesized terms
if r.tok('(', i, o) && r.term(1200, *o, o, &t0) && r.tok(')', *o, o) {
// fmt.Printf("open paren %s close paren\n", t0)
return r.restTerm(0, p, *o, o, t0, t)
}
switch i.Value.Type {
case lex.Int: // integer term §6.3.1.1
n := term.NewInt(i.Value.Content)
*o = i.Next()
return r.restTerm(0, p, *o, o, n, t)
case lex.Float: // float term §6.3.1.1
f := term.NewFloat(i.Value.Content)
*o = i.Next()
return r.restTerm(0, p, *o, o, f, t)
case lex.Atom: // atom term §6.3.1.3
a := term.NewAtomFromLexeme(i.Value.Content)
*o = i.Next()
return r.restTerm(0, p, *o, o, a, t)
case lex.String: // double quated string §6.3.7
cl := term.NewCodeListFromDoubleQuotedString(i.Value.Content)
*o = i.Next()
return r.restTerm(0, p, *o, o, cl, t)
case lex.Variable: // variable term §6.3.2
v := term.NewVar(i.Value.Content)
*o = i.Next()
return r.restTerm(0, p, *o, o, v, t)
case lex.Void: // variable term §6.3.2
v := term.NewVar("_")
*o = i.Next()
return r.restTerm(0, p, *o, o, v, t)
case lex.Comment:
*o = i.Next() // skip the comment
return r.term(p, *o, o, t) // ... and try again
}
// compound term - functional notation §6.3.3
if r.functor(i, o, &f) && r.tok('(', *o, o) {
var args []term.Term
var arg term.Term
for r.term(999, *o, o, &arg) { // 999 priority per §6.3.3.1
args = append(args, arg)
if r.tok(')', *o, o) {
break
}
if r.tok(',', *o, o) {
continue
}
panic("Unexpected content inside compound term arguments")
}
f := term.NewTermFromLexeme(f, args...)
return r.restTerm(0, p, *o, o, f, t)
}
*t = term.NewError("Syntax error", i.Value)
return false
}