swap(x,y)

[Norman Diamond]

In article <1545 at l.cc.purdue.edu> cik at l.cc.purdue.edu (Herman Rubin) writes:

>If one adds a pseudo-op, say use (I will not object to a more appropriate
>term) so that (use int)x means treat x as type int no matter what it was,
>if possible, then it
 [the XOR trick]
>will work on float and pointer, and even swap between,
>say, float and pointer.  If this is modified to allow multiple-word types,
>it could handle double and struct.
>This is another example of keeping the tools from the programmer.

The way to write this pseudo-op in C is:

   *(int*)&x

It still doesn't work if x is longer than an int.  Most hardware does
not supply tools for performing XOR on floating-point registers.  When
Mr. Rubin designs his language, he will have to design a machine to
run it on too.

--
-- 
Norman Diamond, Sony Corporation (diamond at ws.sony.junet)
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