func scm_cond(args *goscm.Pair, env *goscm.Environ) (goscm.SCMT, error) {
for args != goscm.SCM_Nil {
condition, ok := args.Car.(*goscm.Pair)
if !ok {
return goscm.SCM_Nil, errors.New("Expected list")
}
pred, err := condition.Car.Eval(env)
if err != nil {
return goscm.SCM_Nil, err
}
if goscm.SCMTrue(pred) {
consequent_cell, ok := condition.Cdr.(*goscm.Pair)
if !ok {
return goscm.SCM_Nil, errors.New("Cond entry list too short")
}
if consequent_cell.Cdr != goscm.SCM_Nil {
return goscm.SCM_Nil, errors.New("Trailing list elements in cond entry")
}
return consequent_cell.Car, nil
}
args, ok = args.Cdr.(*goscm.Pair)
if !ok {
return goscm.SCM_Nil, errors.New("Condition entries are a dotted list?")
}
}
return goscm.SCM_Nil, nil
}
func scm_or(args *goscm.Pair, env *goscm.Environ) (goscm.SCMT, error) {
if args == goscm.SCM_Nil {
return goscm.NewSCMT(false), nil
}
result, err := args.Car.Eval(env)
if err != nil {
return goscm.SCM_Nil, err
}
if goscm.SCMTrue(result) {
return goscm.NewSCMT(true), nil
}
if reflect.TypeOf(args.Cdr) != reflect.TypeOf(&goscm.Pair{}) {
return goscm.SCM_Nil, errors.New("Expected nil-terminated list")
}
return scm_or(args.Cdr.(*goscm.Pair), env)
}