wip

vendor/github.com/antonmedv/expr/optimizer/fold.go

@@ -0,0 +1,133 @@
+package optimizer
+
+import (
+	"math"
+	"reflect"
+
+	. "github.com/antonmedv/expr/ast"
+	"github.com/antonmedv/expr/file"
+)
+
+type fold struct {
+	applied bool
+	err     *file.Error
+}
+
+func (*fold) Enter(*Node) {}
+func (fold *fold) Exit(node *Node) {
+	patch := func(newNode Node) {
+		fold.applied = true
+		Patch(node, newNode)
+	}
+	// for IntegerNode the type may have been changed from int->float
+	// preserve this information by setting the type after the Patch
+	patchWithType := func(newNode Node, leafType reflect.Type) {
+		patch(newNode)
+		newNode.SetType(leafType)
+	}
+
+	switch n := (*node).(type) {
+	case *UnaryNode:
+		switch n.Operator {
+		case "-":
+			if i, ok := n.Node.(*IntegerNode); ok {
+				patchWithType(&IntegerNode{Value: -i.Value}, n.Node.Type())
+			}
+		case "+":
+			if i, ok := n.Node.(*IntegerNode); ok {
+				patchWithType(&IntegerNode{Value: i.Value}, n.Node.Type())
+			}
+		}
+
+	case *BinaryNode:
+		switch n.Operator {
+		case "+":
+			if a, ok := n.Left.(*IntegerNode); ok {
+				if b, ok := n.Right.(*IntegerNode); ok {
+					patchWithType(&IntegerNode{Value: a.Value + b.Value}, a.Type())
+				}
+			}
+			if a, ok := n.Left.(*StringNode); ok {
+				if b, ok := n.Right.(*StringNode); ok {
+					patch(&StringNode{Value: a.Value + b.Value})
+				}
+			}
+		case "-":
+			if a, ok := n.Left.(*IntegerNode); ok {
+				if b, ok := n.Right.(*IntegerNode); ok {
+					patchWithType(&IntegerNode{Value: a.Value - b.Value}, a.Type())
+				}
+			}
+		case "*":
+			if a, ok := n.Left.(*IntegerNode); ok {
+				if b, ok := n.Right.(*IntegerNode); ok {
+					patchWithType(&IntegerNode{Value: a.Value * b.Value}, a.Type())
+				}
+			}
+		case "/":
+			if a, ok := n.Left.(*IntegerNode); ok {
+				if b, ok := n.Right.(*IntegerNode); ok {
+					if b.Value == 0 {
+						fold.err = &file.Error{
+							Location: (*node).Location(),
+							Message:  "integer divide by zero",
+						}
+						return
+					}
+					patchWithType(&IntegerNode{Value: a.Value / b.Value}, a.Type())
+				}
+			}
+		case "%":
+			if a, ok := n.Left.(*IntegerNode); ok {
+				if b, ok := n.Right.(*IntegerNode); ok {
+					if b.Value == 0 {
+						fold.err = &file.Error{
+							Location: (*node).Location(),
+							Message:  "integer divide by zero",
+						}
+						return
+					}
+					patch(&IntegerNode{Value: a.Value % b.Value})
+				}
+			}
+		case "**":
+			if a, ok := n.Left.(*IntegerNode); ok {
+				if b, ok := n.Right.(*IntegerNode); ok {
+					patch(&FloatNode{Value: math.Pow(float64(a.Value), float64(b.Value))})
+				}
+			}
+		}
+
+	case *ArrayNode:
+		if len(n.Nodes) > 0 {
+
+			for _, a := range n.Nodes {
+				if _, ok := a.(*IntegerNode); !ok {
+					goto string
+				}
+			}
+			{
+				value := make([]int, len(n.Nodes))
+				for i, a := range n.Nodes {
+					value[i] = a.(*IntegerNode).Value
+				}
+				patch(&ConstantNode{Value: value})
+			}
+
+		string:
+			for _, a := range n.Nodes {
+				if _, ok := a.(*StringNode); !ok {
+					return
+				}
+			}
+			{
+				value := make([]string, len(n.Nodes))
+				for i, a := range n.Nodes {
+					value[i] = a.(*StringNode).Value
+				}
+				patch(&ConstantNode{Value: value})
+			}
+
+		}
+	}
+}