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changeset 19286:79d4783a9978

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bitcmp: fix bitwise complement for signed integers. * general/bitcmp.m: current implementation of bitwise complement is broken for signed integers because it uses intmax() as mask for bitxor(). This is incorrect because the last bit of a signed integer is 0 and not 1. Fix this by bitpacking an array of true(). Also simplified input checking by using sizeof, rather than multiple calls to isa(). Added tests for signed integers.
author Carnë Draug <carandraug@octave.org>
date Mon, 13 Oct 2014 13:40:44 +0100
parents 91a6f06c5052
children 6d8d5d9f2264
files scripts/general/bitcmp.m
diffstat 1 files changed, 11 insertions(+), 20 deletions(-) [+]
line wrap: on
line diff
--- a/scripts/general/bitcmp.m	Thu Oct 09 20:38:04 2014 -0700
+++ b/scripts/general/bitcmp.m	Mon Oct 13 13:40:44 2014 +0100
@@ -31,6 +31,7 @@
 ##   @result{} 110100
 ## @end group
 ## @end example
+##
 ## @seealso{bitand, bitor, bitxor, bitset, bitget, bitcmp, bitshift, bitmax}
 ## @end deftypefn
 
@@ -52,27 +53,11 @@
   elseif (isa (A, "single"))
     bmax = bitmax ("single");
     amax = ceil (log2 (bmax));
+  elseif (isinteger (A))
+    amax = sizeof (ones (1, class (A))) * 8;
+    bmax = bitpack (true (amax, 1), class (A));
   else
-    if (isa (A, "uint8"))
-      amax = 8;
-    elseif (isa (A, "uint16"))
-      amax = 16;
-    elseif (isa (A, "uint32"))
-      amax = 32;
-    elseif (isa (A, "uint64"))
-      amax = 64;
-    elseif (isa (A, "int8"))
-      amax = 8;
-    elseif (isa (A, "int16"))
-      amax = 16;
-    elseif (isa (A, "int32"))
-      amax = 32;
-    elseif (isa (A, "int64"))
-      amax = 64;
-    else
-      error ("bitcmp: invalid class %s", class (A));
-    endif
-    bmax = intmax (class (A));
+    error ("bitcmp: invalid class %s", class (A));
   endif
 
   if (nargin == 1 || k == amax)
@@ -131,3 +116,9 @@
 %! assert (bitcmp (A,Amax-1), bitshift (uint64 (1),Amax-2));
 %! assert (bitcmp (A,Amax-2), uint64 (0));
 
+## Do not forget signed integers
+%!assert (bitcmp (int8 (127)), int8 (-128)) # [1 1 1 1 1 1 1 0]
+%!assert (bitcmp (int8 (1)), int8 (-2))     # [1 0 0 0 0 0 0 0]
+%!assert (bitcmp (int8 (0)), int8 (-1))     # [0 0 0 0 0 0 0 0]
+%!assert (bitcmp (int8 (8)), int8 (-9))     # [0 0 0 1 0 0 0 0]
+