From ff71246139837ff3fd9495dff6a77b9f65cb34c0 Mon Sep 17 00:00:00 2001
From: Qi Xiao <xiaqqaix@gmail.com>
Date: Sat, 3 Feb 2018 22:47:08 -0800
Subject: [PATCH] eval: Convert return values in ReflectBuiltinFn.

---
 eval/builtin_fn_num.go          | 39 +++++++++++----------------------
 eval/reflect_builtin_fn.go      | 18 +++++++++++++--
 eval/reflect_builtin_fn_test.go | 12 ++++++++++
 3 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/eval/builtin_fn_num.go b/eval/builtin_fn_num.go
index c871828e..4dadacce 100644
--- a/eval/builtin_fn_num.go
+++ b/eval/builtin_fn_num.go
@@ -3,7 +3,6 @@ package eval
 import (
 	"math"
 	"math/rand"
-	"strconv"
 )
 
 // Numerical operations.
@@ -22,11 +21,11 @@ func init() {
 		"+": plus,
 		"-": minus,
 		"*": times,
-		"^": pow,
-		"%": mod,
+		"^": math.Pow,
+		"%": func(a, b int) int { return a % b },
 
 		// Random
-		"rand":    randFn,
+		"rand":    rand.Float64,
 		"randint": randint,
 	})
 	addToBuiltinFns([]*BuiltinFn{
@@ -34,31 +33,31 @@ func init() {
 	})
 }
 
-func plus(nums ...float64) string {
+func plus(nums ...float64) float64 {
 	sum := 0.0
 	for _, f := range nums {
 		sum += f
 	}
-	return floatToString(sum)
+	return sum
 }
 
-func minus(sum float64, nums ...float64) string {
+func minus(sum float64, nums ...float64) float64 {
 	if len(nums) == 0 {
 		// Unary -
-		return floatToString(-sum)
+		return -sum
 	}
 	for _, f := range nums {
 		sum -= f
 	}
-	return floatToString(sum)
+	return sum
 }
 
-func times(nums ...float64) string {
+func times(nums ...float64) float64 {
 	prod := 1.0
 	for _, f := range nums {
 		prod *= f
 	}
-	return floatToString(prod)
+	return prod
 }
 
 func slash(ec *Frame, args []interface{}, opts map[string]interface{}) {
@@ -87,21 +86,9 @@ func divide(ec *Frame, args []interface{}, opts map[string]interface{}) {
 	out <- floatToString(prod)
 }
 
-func pow(b, p float64) string {
-	return floatToString(math.Pow(b, p))
-}
-
-func mod(a, b int) string {
-	return strconv.Itoa(a % b)
-}
-
-func randFn() string {
-	return floatToString(rand.Float64())
-}
-
-func randint(low, high int) (string, error) {
+func randint(low, high int) (int, error) {
 	if low >= high {
-		return "", ErrArgs
+		return 0, ErrArgs
 	}
-	return strconv.Itoa(low + rand.Intn(high-low)), nil
+	return low + rand.Intn(high-low), nil
 }
diff --git a/eval/reflect_builtin_fn.go b/eval/reflect_builtin_fn.go
index 340c30eb..c4c7d8d3 100644
--- a/eval/reflect_builtin_fn.go
+++ b/eval/reflect_builtin_fn.go
@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"strconv"
 	"unsafe"
 
 	"github.com/elves/elvish/eval/types"
@@ -33,7 +34,8 @@ func addToReflectBuiltinFns(moreFns map[string]interface{}) {
 // Return values go to the channel part of the stdout port. However, if the last
 // return value has type error and is not nil, it is turned into an exception
 // and no ouputting happens. If the last return value is a nil error, it is
-// ignored.
+// ignored. Return values of type int or float64 are converted to strings with
+// strconv.Itoa and strconv.FormatFloat(f, 'g', -1, 64) respectively.
 type ReflectBuiltinFn struct {
 	name string
 	impl interface{}
@@ -157,7 +159,7 @@ func (b *ReflectBuiltinFn) Call(f *Frame, args []interface{}, opts map[string]in
 	}
 
 	for _, out := range outs {
-		f.OutputChan() <- out.Interface()
+		f.OutputChan() <- convertRet(out.Interface())
 	}
 	return nil
 }
@@ -188,3 +190,15 @@ func convertArg(arg interface{}, typ reflect.Type) (interface{}, error) {
 			types.Kind(reflect.Zero(typ).Interface()), types.Kind(arg))
 	}
 }
+
+// convertRet converts the return value.
+func convertRet(ret interface{}) interface{} {
+	switch ret := ret.(type) {
+	case int:
+		return strconv.Itoa(ret)
+	case float64:
+		return strconv.FormatFloat(ret, 'g', -1, 64)
+	default:
+		return ret
+	}
+}
diff --git a/eval/reflect_builtin_fn_test.go b/eval/reflect_builtin_fn_test.go
index 5120deaf..dcf78b10 100644
--- a/eval/reflect_builtin_fn_test.go
+++ b/eval/reflect_builtin_fn_test.go
@@ -95,6 +95,18 @@ func TestReflectBuiltinFnCall(t *testing.T) {
 		t.Errorf("Return value is not outputted")
 	}
 
+	// Conversion of return values.
+	f = NewReflectBuiltinFn("f", func() int { return 314 })
+	callGood(outFrame, nil, theOptions)
+	select {
+	case ret := <-ch:
+		if ret != "314" {
+			t.Errorf("Return value is not converted to string")
+		}
+	default:
+		t.Errorf("Return value is not outputted")
+	}
+
 	// Passing of error return value.
 	theError := errors.New("the error")
 	f = NewReflectBuiltinFn("f", func() (string, error) {