added

vendor/github.com/glycerine/zygomys/zygo/datastack.go

@@ -0,0 +1,75 @@
+package zygo
+
+import (
+	"errors"
+	"fmt"
+)
+
+type DataStackElem struct {
+	expr Sexp
+}
+
+func (d DataStackElem) IsStackElem() {}
+
+func (stack *Stack) PushExpr(expr Sexp) {
+	stack.Push(DataStackElem{expr})
+}
+
+func (stack *Stack) PushExpressions(expr []Sexp) error {
+	for _, x := range expr {
+		stack.Push(DataStackElem{x})
+	}
+	return nil
+}
+
+func (stack *Stack) PopExpr() (Sexp, error) {
+	elem, err := stack.Pop()
+	if err != nil {
+		return nil, err
+	}
+	return elem.(DataStackElem).expr, nil
+}
+
+func (stack *Stack) GetExpressions(n int) ([]Sexp, error) {
+	stack_start := stack.tos - n + 1
+	if stack_start < 0 {
+		return nil, errors.New("not enough items on stack")
+	}
+	arr := make([]Sexp, n)
+	for i := 0; i < n; i++ {
+		arr[i] = stack.elements[stack_start+i].(DataStackElem).expr
+	}
+	return arr, nil
+}
+
+func (stack *Stack) PopExpressions(n int) ([]Sexp, error) {
+	origSz := stack.Size()
+	expressions, err := stack.GetExpressions(n)
+	if err != nil {
+		return nil, err
+	}
+	stack.TruncateToSize(origSz - n)
+	return expressions, nil
+}
+
+func (stack *Stack) GetExpr(n int) (Sexp, error) {
+	elem, err := stack.Get(n)
+	if err != nil {
+		return nil, err
+	}
+	return elem.(DataStackElem).expr, nil
+}
+
+func (stack *Stack) PrintStack() {
+	for i := 0; i <= stack.tos; i++ {
+		expr := stack.elements[i].(DataStackElem).expr
+		fmt.Println("\t" + expr.SexpString(nil))
+	}
+}
+
+func (stack *Stack) PrintScopeStack() {
+	for i := 0; i <= stack.tos; i++ {
+		scop := stack.elements[i].(*Scope)
+		scop.Show(stack.env, NewPrintStateWithIndent(4), "")
+	}
+}