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digitalmars.D.learn - single loop copy in D

reply psychoticRabbit <meagain meagain.com> writes:
trying to do this C code, in D, but getting error:
"Error: assignment cannot be used as a condition, perhaps `==` 
was meant?"

any help much appreciated:

------
while ((*dst++ = *src++)) {}
------
Mar 02 2018
next sibling parent Andrea Fontana <nospam example.com> writes:
On Friday, 2 March 2018 at 09:44:20 UTC, psychoticRabbit wrote:

 trying to do this C code, in D, but getting error:
 "Error: assignment cannot be used as a condition, perhaps `==` 
 was meant?"

 any help much appreciated:

 ------
 while ((*dst++ = *src++)) {}
 ------


You can't use this syntax inside a while/if/... to prevent 
mistakes due to similarity between assignment syntax (=) and 
comparison syntax (==)

Andrea
Mar 02 2018
prev sibling parent reply Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Friday, March 02, 2018 09:44:20 psychoticRabbit via Digitalmars-d-learn 
wrote:

 trying to do this C code, in D, but getting error:
 "Error: assignment cannot be used as a condition, perhaps `==`
 was meant?"

 any help much appreciated:

 ------
 while ((*dst++ = *src++)) {}
 ------


You can't use = in a while loop's condition like that in D, regardless of
what you do with parens. You'll need to refactor the code so that the
assignment is done in the loop's body.

- Jonathan M Davis
Mar 02 2018
parent reply Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:
On Friday, 2 March 2018 at 10:01:34 UTC, Jonathan M Davis wrote:

 On Friday, March 02, 2018 09:44:20 psychoticRabbit via 
 Digitalmars-d-learn wrote:

 trying to do this C code, in D, but getting error:
 "Error: assignment cannot be used as a condition, perhaps `==`
 was meant?"

 any help much appreciated:

 ------
 while ((*dst++ = *src++)) {}
 ------


 You can't use = in a while loop's condition like that in D, 
 regardless of what you do with parens. You'll need to refactor 
 the code so that the assignment is done in the loop's body.


This is of course only partly true.

while ((*dst++ = *src++) != 0) {}

works just great, and also better shows what's actually being 
tested for in the loop.

--
   Simen
Mar 02 2018
parent psychoticRabbit <meagain meagain.com> writes:
On Friday, 2 March 2018 at 10:08:57 UTC, Simen Kjærås wrote:

 This is of course only partly true.

 while ((*dst++ = *src++) != 0) {}

 works just great, and also better shows what's actually being 
 tested for in the loop.

 --
   Simen


That's what I was after. Thanks!
Mar 02 2018