func lambda(s *scheme.Scope, ss []scheme.Sexpr) (scheme.Sexpr, error) {
if len(ss) < 2 {
return nil, scheme.ProcError("lambda at least 2 arguments")
}
exprs := ss[1:]
evalScopeParent := scheme.NewScope(s)
lArgs := ss[0]
f := func(callScope *scheme.Scope, ss []scheme.Sexpr) (scheme.Sexpr, error) {
args := lArgs
evalScope := scheme.NewScope(evalScopeParent)
aC, ok := args.(*scheme.Cons)
for args != scheme.Nil {
if len(ss) == 0 {
return nil, scheme.ProcError("invalid number of arguments")
}
if !ok {
val := scheme.Unflatten(ss)
s, k := args.(*scheme.Symbol)
if !k {
return nil, scheme.ProcError("Invalid parameter specification")
}
evalScope.Define(s, val)
goto done
}
arg := aC.Car
val := ss[0]
s, k := arg.(*scheme.Symbol)
if !k {
return nil, scheme.ProcError("invalid parameter specification")
}
evalScope.Define(s, val)
ss = ss[1:]
args = aC.Cdr
aC, ok = args.(*scheme.Cons)
}
if len(ss) > 0 {
return nil, scheme.ProcError("Invalid number of arguments")
}
done:
for _, e := range exprs[0 : len(exprs)-1] {
eval.Eval(evalScope, e)
}
return eval.Eval(evalScope, exprs[len(exprs)-1])
}
return scheme.CreateFunction(f, "lamba"), nil
}
func let(s *scheme.Scope, ss []scheme.Sexpr) (scheme.Sexpr, error) {
if len(ss) < 1 {
return nil, scheme.ProcError("let requires at least one argument")
}
evalScope := scheme.NewScope(s)
bindings, err := scheme.Flatten(ss[0])
if err != nil {
return nil, err
}
for _, b := range bindings {
bs, err := scheme.Flatten(b)
if err != nil {
return nil, err
}
if len(bs) != 2 {
return nil, scheme.ProcError("invalid binding on let")
}
sym, ok := bs[0].(*scheme.Symbol)
if !ok {
return nil, scheme.ProcError("invalid binding on let")
}
val, err := eval.Eval(s, bs[1])
if err != nil {
return nil, err
}
evalScope.Define(sym, val)
}
prog := ss[1:]
var last scheme.Sexpr = scheme.Nil
for _, l := range prog {
last, err = eval.Eval(evalScope, l)
if err != nil {
return nil, err
}
}
return last, nil
}