🚀 go-pugleaf

In article <1992Sep29.222521.9221@kai.com> david@kai.com (David Nelson) writes:
>[...] what about: "a = b[i+=1,i] + c[i+=1,i];".

The commas introduce sequence points, but they might occur in either order,
or they might even occur simultaneously.  For example, a hypothetical
implementation could order the operations as:
  [previous sequence point]
  i+=1
  i+=1
  , sequence point
  , sequence point
  fetch i
  compute address of c[i] and fetch it
  remember fetched i (or fetch again if volatile; might occur earlier)
  compute address of b[i] and fetch it
  add
  assign to a
  ; sequence point
The two modifications to the stored value between the previous sequence
point and the first sequence point visible here violate this "shall":
>From ANSI 3.3 Expressions
>     Between the previous and next sequence point an object shall have its
> stored value modified at most once by the evaluation of an expression. 

... and your program might post an "F*** you all" message to alt.pictures.

>My interpretation would be that the sequence point only affects the
>subexpression of the operation that introduced the sequence point.

I think you mean the subexpression[s] that are operand[s] of the operation
that introduced the sequence point -- for example, comma takes two operands.
That would have been a very nice definition (in my personal opinion).
The standard didn't do it that way though.
--
Norman Diamond       diamond@jit081.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.
"Yeah -- bad wiring.  That was probably it.  Very bad."