Commit inicial

main.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+var source = `
+	(+ 1 2 3 4)
+	`
+
+func (v *Value[T]) Step() (Expression, error) {
+	return v, nil
+}
+
+func (v *Quoted) Step() (Expression, error) {
+	return v, nil
+}
+
+func (d *Declaration) Step() (Expression, error) {
+	return &Value[int]{0}, nil
+}
+
+func (v *Identifier) Step() (Expression, error) {
+	switch v.value {
+	case "+":
+		f := func(args []Expression) (Expression, error) {
+			sum := 0
+			for _, arg := range args {
+				if !isValue(arg) {
+					panic("!")
+				}
+				switch x := arg.(type) {
+				case *Value[int]:
+					sum += x.value
+				case *Value[*Int]:
+					sum += x.value.value
+				default:
+					return nil, fmt.Errorf("invalid type")
+
+				}
+			}
+			return &Value[int]{sum}, nil
+		}
+		return &Value[Function]{f}, nil
+	default:
+		panic("!")
+	}
+}
+
+func (v *List) Step() (Expression, error) {
+	for i, expr := range v.els {
+		if !isValue(expr) {
+			e, err := expr.Step()
+			if err != nil {
+				return nil, err
+			}
+			v.els[i] = e
+			return v, nil
+		}
+	}
+	if len(v.els) == 0 {
+		return nil, fmt.Errorf("empty list")
+	}
+	f, ok := v.els[0].(*Value[Function])
+	if !ok {
+		return nil, fmt.Errorf("not a function")
+	}
+	r, err := f.value(v.els[1:])
+	if err != nil {
+		return nil, err
+	}
+	return r, nil
+}
+
+func isValue(e Expression) bool {
+	switch e.(type) {
+	case *Value[int], *Value[*Int], *Value[Function], *Quoted:
+		return true
+	default:
+		return false
+	}
+}
+
+func fullStep(e Expression) (Expression, error) {
+	for !isValue(e) {
+		n, err := e.Step()
+		if err != nil {
+			return n, nil
+		}
+		e = n
+	}
+	return e, nil
+}
+
+func main() {
+	if len(os.Args) > 1 {
+		source = os.Args[1]
+	}
+	tk, err := lex(source)
+	if err != nil {
+		panic(err)
+	}
+	p, err := consume(tk)
+	if err != nil {
+		panic(err)
+	}
+	s, err := p.Step()
+	if err != nil {
+		panic(err)
+	}
+	result, err := fullStep(s)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(result)
+}