code review 881050: big: Add Lsh and Value; convert pidigits to use big

src/pkg/big/nat.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.
 
 // This file contains operations on unsigned multi-precision integers.
 // These are the building blocks for the operations on signed integers
 // and rationals.
 
 // This package implements multi-precision arithmetic (big numbers).
 // The following numeric types are supported:
@@ skipping 521 matching lines @@
 
 // To avoid losing the top n bits, dst should be sized so that
 // len(dst) == len(src) + 1.
 func shiftLeft(dst, src []Word, n uint) {
         if len(src) == 0 {
                 return
         }
 
         ñ := _W - n
         if len(dst) > len(src) {
-                dst[len(dst)-1] |= src[len(src)-1] >> ñ
+                dst[len(src)] |= src[len(src)-1] >> ñ
         }
         for i := len(src) - 1; i >= 1; i-- {
-                dst[i] = src[i] << n | src[i-1] >> ñ
+                dst[i] = src[i]<<n | src[i-1]>>ñ
         }
         dst[0] = src[0] << n
 }
 
 
 func shiftRight(dst, src []Word, n uint) {
         if len(src) == 0 {
                 return
         }
 
         ñ := _W - n
         for i := 0; i < len(src)-1; i++ {
-                dst[i] = src[i] >> n | src[i+1] << ñ
+                dst[i] = src[i]>>n | src[i+1]<<ñ
         }
         dst[len(src)-1] = src[len(src)-1] >> n
 }
 
 
 // greaterThan returns true iff (x1<<_W + x2) > (y1<<_W + y2)
 func greaterThan(x1, x2, y1, y2 Word) bool { return x1 > y1 || x1 == y1 && x2 > y2 }
 
 
 // modNW returns x % d.
@@ skipping 213 matching lines @@
                         }
                         if cmpNN(y, bigOne) == 0 {
                                 return false
                         }
                 }
                 return false
         }
 
         return true
 }