func Eval(sc *scheme.Scope, e scheme.Sexpr) (scheme.Sexpr, error) {
//e = transform(sc, e)
switch e := e.(type) {
case *scheme.Cons:
cons := e
car, err := Eval(sc, cons.Car)
if err != nil {
return nil, err
}
if !isFunction(car) && !isPrim(car) {
return nil, evalError("Attempted application on non-function")
}
cdr := cons.Cdr
args, err := scheme.Flatten(cdr)
if err != nil {
return nil, err
}
if isPrim(car) {
return car.(*scheme.Primitive).Procedure()(sc, args)
}
f := car.(*scheme.Function).Procedure()
for i, a := range args {
args[i], err = Eval(sc, a)
if err != nil {
return nil, err
}
}
return f(sc, args)
case *scheme.Symbol:
return sc.Lookup(e)
}
return e, nil
}
func define(s *scheme.Scope, args []scheme.Sexpr) (scheme.Sexpr, error) {
if len(args) != 2 {
return nil, scheme.ProcError("define requires exactly 2 arguments")
}
idSym, ok := args[0].(*scheme.Symbol)
if !ok {
return nil, scheme.ProcError("invalid argument to define")
}
val, err := eval.Eval(s, args[1])
if err != nil {
return nil, err
}
s.DefineHigh(idSym, val)
return scheme.Nil, nil
}