Hello,
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
Thankx a lot..
Jason.
19  14902 
Jason wrote: Hello,
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
*ptr++ means "Fetch the thing that `ptr' points to, and
increment `ptr' so it points to the next thing."
++*ptr means "Increment the thing `ptr' points to, and
leave `ptr' itself unchanged."
-- Er*********@sun .com
Eric Sosman wrote: Jason wrote:
Hello,
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
*ptr++ means "Fetch the thing that `ptr' points to, and
increment `ptr' so it points to the next thing."
++*ptr means "Increment the thing `ptr' points to, and
leave `ptr' itself unchanged."
The second expression is unambiguous even if you don't remember the
precedence rules or evaluation order. When it comes to the first
expression I'd increment ptr in a separate statement (even though most C
programmers love multiple side-effects).
-- August
On Sun, 15 May 2005 15:09:49 GMT, August Karlstrom
<fu********@com hem.se> wrote: Eric Sosman wrote: Jason wrote:
Hello,
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
*ptr++ means "Fetch the thing that `ptr' points to, and
increment `ptr' so it points to the next thing."
++*ptr means "Increment the thing `ptr' points to, and
leave `ptr' itself unchanged."
The second expression is unambiguous even if you don't remember the
precedence rules or evaluation order. When it comes to the first
expression I'd increment ptr in a separate statement (even though most C
programmers love multiple side-effects).
-- August
Ok - Thank you for the answers
Jason.S.
August Karlstrom <fu********@com hem.se> writes: Jason wrote:
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
The second expression is unambiguous even if you don't remember the
precedence rules or evaluation order. When it comes to the first
expression I'd increment ptr in a separate statement (even though most
C programmers love multiple side-effects).
Each of *ptr++ and ++*ptr has only a single side effect.
--
Ben Pfaff
email: bl*@cs.stanford .edu
web: http://benpfaff.org
August Karlstrom wrote: Eric Sosman wrote: Jason wrote:
Hello,
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
*ptr++ means "Fetch the thing that `ptr' points to, and
increment `ptr' so it points to the next thing."
++*ptr means "Increment the thing `ptr' points to, and
leave `ptr' itself unchanged."
The second expression is unambiguous even if you don't remember the
precedence rules or evaluation order. When it comes to the first
expression I'd increment ptr in a separate statement (even though most C
programmers love multiple side-effects).
`*ptr++` is the standard C idiom for fetch-and-advance-pointer.
Incrementing in a separate statement is likely to make the code more
confusing, I'd have thought.
--
Chris "electric hedgehog" Dollin
"The compiler is free to insert padding because it makes the struct
look bigger and scares away predators." [Keith Thompson, comp.lang.c]
August Karlstrom wrote:
Eric Sosman wrote: Jason wrote:
Hello,
could someone explain the difference to me inbetween:
*ptr++ and ++*ptr
*ptr++ means "Fetch the thing that `ptr' points to, and
increment `ptr' so it points to the next thing."
++*ptr means "Increment the thing `ptr' points to, and
leave `ptr' itself unchanged."
The second expression is unambiguous even if you don't remember the
precedence rules or evaluation order.
There is no evaluation order.
Assignment is not a sequence point.
This expression
*ptr++
has a value and a side effect.
The side effect is that ptr is incremented.
The value of the expression is the value of what ptr points to,
prior to being incremented,
but that evaluation can be made before
or after the side effect takes place.
--
pete
Ben Pfaff wrote: Each of *ptr++ and ++*ptr has only a single side effect.
Correct. When `*ptr++' (as well as `++*ptr') is part of a statement
(with assignment, procedure calls etc.) though, it (the statement) will
most likely have multiple side effects. The expression `*ptr++' as
opposed to `++*ptr' doesn't make sense as a single statement (why would
you want to dereference the pointer if you don't use it).
-- August
Chris Dollin wrote: `*ptr++` is the standard C idiom for fetch-and-advance-pointer.
Incrementing in a separate statement is likely to make the code more
confusing, I'd have thought.
Confusing for the programmer who only has experience with C/C++, maybe.
In almost any other language (procedural at the statement level) the
incrementation is a separate statement.
-- August This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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