#96, allows node-set numeric operator on +, -, *, MOD(), DIV()

build.go

@@ -665,7 +665,7 @@ func (b *builder) processOperator(root *operatorNode, props *builderProp) (query
 	var qyOutput query
 	switch root.Op {
 	case "+", "-", "*", "div", "mod": // Numeric operator
-		var exprFunc func(interface{}, interface{}) interface{}
+		var exprFunc func(iterator, interface{}, interface{}) interface{}
 		switch root.Op {
 		case "+":
 			exprFunc = plusFunc

operator.go

@@ -1,7 +1,6 @@
 package xpath
 
 import (
-	"reflect"
 	"strconv"
 )
 
@@ -247,44 +246,43 @@ var orFunc = func(t iterator, m, n interface{}) interface{} {
 	return logicalFuncs[t1][t2](t, "or", m, n)
 }
 
-func numericExpr(m, n interface{}, cb func(float64, float64) float64) float64 {
-	typ := reflect.TypeOf(float64(0))
-	a := reflect.ValueOf(m).Convert(typ)
-	b := reflect.ValueOf(n).Convert(typ)
-	return cb(a.Float(), b.Float())
+func numericExpr(t iterator, m, n interface{}, cb func(float64, float64) float64) float64 {
+	a := asNumber(t, m)
+	b := asNumber(t, n)
+	return cb(a, b)
 }
 
 // plusFunc is an `+` operator.
-var plusFunc = func(m, n interface{}) interface{} {
-	return numericExpr(m, n, func(a, b float64) float64 {
+var plusFunc = func(t iterator, m, n interface{}) interface{} {
+	return numericExpr(t, m, n, func(a, b float64) float64 {
 		return a + b
 	})
 }
 
 // minusFunc is an `-` operator.
-var minusFunc = func(m, n interface{}) interface{} {
-	return numericExpr(m, n, func(a, b float64) float64 {
+var minusFunc = func(t iterator, m, n interface{}) interface{} {
+	return numericExpr(t, m, n, func(a, b float64) float64 {
 		return a - b
 	})
 }
 
 // mulFunc is an `*` operator.
-var mulFunc = func(m, n interface{}) interface{} {
-	return numericExpr(m, n, func(a, b float64) float64 {
+var mulFunc = func(t iterator, m, n interface{}) interface{} {
+	return numericExpr(t, m, n, func(a, b float64) float64 {
 		return a * b
 	})
 }
 
 // divFunc is an `DIV` operator.
-var divFunc = func(m, n interface{}) interface{} {
-	return numericExpr(m, n, func(a, b float64) float64 {
+var divFunc = func(t iterator, m, n interface{}) interface{} {
+	return numericExpr(t, m, n, func(a, b float64) float64 {
 		return a / b
 	})
 }
 
 // modFunc is an 'MOD' operator.
-var modFunc = func(m, n interface{}) interface{} {
-	return numericExpr(m, n, func(a, b float64) float64 {
+var modFunc = func(t iterator, m, n interface{}) interface{} {
+	return numericExpr(t, m, n, func(a, b float64) float64 {
 		return float64(int(a) % int(b))
 	})
 }

query.go

@@ -999,7 +999,7 @@ func (l *logicalQuery) Properties() queryProp {
 type numericQuery struct {
 	Left, Right query
 
-	Do func(interface{}, interface{}) interface{}
+	Do func(iterator, interface{}, interface{}) interface{}
 }
 
 func (n *numericQuery) Select(t iterator) NodeNavigator {
@@ -1009,7 +1009,7 @@ func (n *numericQuery) Select(t iterator) NodeNavigator {
 func (n *numericQuery) Evaluate(t iterator) interface{} {
 	m := n.Left.Evaluate(t)
 	k := n.Right.Evaluate(t)
-	return n.Do(m, k)
+	return n.Do(t, m, k)
 }
 
 func (n *numericQuery) Clone() query {

xpath_test.go

@@ -3,6 +3,7 @@ package xpath
 import (
 	"bytes"
 	"fmt"
+	"math"
 	"sort"
 	"strings"
 	"testing"
@@ -235,6 +236,28 @@ func TestMustCompile(t *testing.T) {
 	}
 }
 
+func Test_plusFunc(t *testing.T) {
+	// 1+1
+	assertEqual(t, float64(2), plusFunc(nil, float64(1), float64(1)))
+	// string +
+	assertEqual(t, float64(2), plusFunc(nil, "1", "1"))
+	// invalid string
+	v := plusFunc(nil, "a", 1)
+	assertTrue(t, math.IsNaN(v.(float64)))
+	// Nodeset
+	// TODO
+}
+
+func Test_minusFunc(t *testing.T) {
+	// 1 - 1
+	assertEqual(t, float64(0), minusFunc(nil, float64(1), float64(1)))
+	// string
+	assertEqual(t, float64(0), minusFunc(nil, "1", "1"))
+	// invalid string
+	v := minusFunc(nil, "a", 1)
+	assertTrue(t, math.IsNaN(v.(float64)))
+}
+
 func TestNodeType(t *testing.T) {
 	tests := []struct {
 		expr     string