patch.patch

diff --git a/topdown/arithmetic.go b/topdown/arithmetic.go
index c75f816a4..b0061074f 100644
--- a/topdown/arithmetic.go
+++ b/topdown/arithmetic.go
@@ -6,6 +6,7 @@ package topdown
 
 import (
 	"math/big"
+	"strconv"
 
 	"fmt"
 
@@ -113,6 +114,42 @@ func builtinArithArity2(fn arithArity2) BuiltinFunc {
 	}
 }
 
+var Ints map[string]int
+var Snti map[int]string
+
+func init() {
+	Ints = make(map[string]int, 256)
+	Snti = make(map[int]string, 256)
+	for i := 0; i < 256; i++ {
+		j := strconv.Itoa(i)
+		Ints[j] = i
+		Snti[i] = j
+	}
+}
+
+func builtinArithPlus(_ BuiltinContext, operands []*ast.Term, iter func(*ast.Term) error) error {
+	n1, err := builtins.NumberOperand(operands[0].Value, 1)
+	if err != nil {
+		return err
+	}
+	n2, err := builtins.NumberOperand(operands[1].Value, 2)
+	if err != nil {
+		return err
+	}
+	if f, ok := Ints[string(n1)]; ok {
+		if g, ok := Ints[string(n2)]; ok {
+			if h, ok := Snti[f+g]; ok {
+				return iter(ast.NewTerm(ast.Number(h)))
+			}
+		}
+	}
+	f, err := arithPlus(builtins.NumberToFloat(n1), builtins.NumberToFloat(n2))
+	if err != nil {
+		return err
+	}
+	return iter(ast.NewTerm(builtins.FloatToNumber(f)))
+}
+
 func builtinMinus(_ BuiltinContext, operands []*ast.Term, iter func(*ast.Term) error) error {
 
 	n1, ok1 := operands[0].Value.(ast.Number)
@@ -176,7 +213,7 @@ func init() {
 	RegisterBuiltinFunc(ast.Round.Name, builtinArithArity1(arithRound))
 	RegisterBuiltinFunc(ast.Ceil.Name, builtinArithArity1(arithCeil))
 	RegisterBuiltinFunc(ast.Floor.Name, builtinArithArity1(arithFloor))
-	RegisterBuiltinFunc(ast.Plus.Name, builtinArithArity2(arithPlus))
+	RegisterBuiltinFunc(ast.Plus.Name, builtinArithPlus)
 	RegisterBuiltinFunc(ast.Minus.Name, builtinMinus)
 	RegisterBuiltinFunc(ast.Multiply.Name, builtinArithArity2(arithMultiply))
 	RegisterBuiltinFunc(ast.Divide.Name, builtinArithArity2(arithDivide))