[myhdl-list] myhdl.concat

[Thomas H. <th...@ct...>]

I expected myhdl.concat to return a bit-wise concatenation of the arguments.
However, when I use concat(unsigned, signed) this is not the case.
The following program prints '7FFFFFFD' instead of '8FFFFFFD':

<code>
#!/usr/bin/python2.7-32
# -*- coding: utf-8 -*-

import myhdl

def unsigned(width, value=0, cls=myhdl.intbv):
     """Create an unsigned signal based on a bitvector with the
     specified width and initial value.
     """
     return myhdl.Signal(cls(value, 0, 2**width))

def signed(width, value=0, cls=myhdl.intbv):
     """Create an signed signal based on a bitvector with the
     specified width and initial value.
     """
     return myhdl.Signal(cls(value, -2**(width-1), 2**(width-1)))

a = unsigned(4, 8)
b = signed(28, -3)

print "%08X" % myhdl.concat(a, b)
</code>

Is this correct?  Changing (in myhdl 0.8, module _concat.py) this line
gives the result that I expected:

--- _concat.py~ Mon Aug  4 12:20:26 2014
+++ _concat.py  Sat Aug  9 10:15:05 2014
@@ -65,7 +65,7 @@
          if not w:
              raise TypeError, "concat: arg on pos %d should have 
length" % (i+1)
          width += w
-        val = val*(2**w) + v
+        val = val*(2**w) | (v % 2**len(v))

      if basewidth:
          return intbv(val, _nrbits=basewidth + width)


Thomas