code review 5907047: effective_go: cleanups and fixes

doc/progs/eff_bytesize.go

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package main
 
 import "fmt"
 
 type ByteSize float64
 
 const (
         _           = iota // ignore first value by assigning to blank identifier
         KB ByteSize = 1 << (10 * iota)
         MB
         GB
         TB
         PB
         EB
         ZB
         YB
 )
 
 func (b ByteSize) String() string {
         switch {
         case b >= YB:
-                return fmt.Sprintf("%.2fYB", float64(b/YB))
+                return fmt.Sprintf("%.2fYB", b/YB)
         case b >= ZB:
-                return fmt.Sprintf("%.2fZB", float64(b/ZB))
+                return fmt.Sprintf("%.2fZB", b/ZB)
         case b >= EB:
-                return fmt.Sprintf("%.2fEB", float64(b/EB))
+                return fmt.Sprintf("%.2fEB", b/EB)
         case b >= PB:
-                return fmt.Sprintf("%.2fPB", float64(b/PB))
+                return fmt.Sprintf("%.2fPB", b/PB)
         case b >= TB:
-                return fmt.Sprintf("%.2fTB", float64(b/TB))
+                return fmt.Sprintf("%.2fTB", b/TB)
         case b >= GB:
-                return fmt.Sprintf("%.2fGB", float64(b/GB))
+                return fmt.Sprintf("%.2fGB", b/GB)
         case b >= MB:
-                return fmt.Sprintf("%.2fMB", float64(b/MB))
+                return fmt.Sprintf("%.2fMB", b/MB)
         case b >= KB:
-                return fmt.Sprintf("%.2fKB", float64(b/KB))
+                return fmt.Sprintf("%.2fKB", b/KB)
         }
-        return fmt.Sprintf("%.2fB", float64(b))
+        return fmt.Sprintf("%.2fB", b)
 }
 
 func main() {
         fmt.Println(YB, ByteSize(1e13))
 }