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diff scripts/general/bitcmp.m @ 19444:79d4783a9978

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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 d63878346099
children 4197fc428c7d
line wrap: on
line diff
--- a/scripts/general/bitcmp.m
+++ b/scripts/general/bitcmp.m
@@ -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]
+