Is it now common practice to use conditional statements like
if (0 == i)
if (-1 == i)
if (true == i)
if (5 == i)
over the more traditional statements like
if (i == 0)
if (i == -1)
if (i == true)
if (i == 5)
for all types of 'i' (PODs and classes)?
41  1589 
On Sun, 4 May 2008 22:40:28 -0400, "barcarolle r"
<ba*********@mu sic.netwrote in comp.lang.c++:
Is it now common practice to use conditional statements like
if (0 == i)
if (-1 == i)
if (true == i)
if (5 == i)
over the more traditional statements like
if (i == 0)
if (i == -1)
if (i == true)
if (i == 5)
for all types of 'i' (PODs and classes)?
The reason for writing the constant first in an equality comparison is
quite simple. A fairly common typographical error is type only one
'=' once in a while when two are intended, and needed.
Consider the implications of accidentally typing:
if (i = 0)
....when you meant to type:
if (i == 0)
Assuming a built-in type, or even a class type having an assignment
operator accepting an int, then the first version, the type, is not
only always false, but it also destroys the existing value of 'i'. Yet
it is syntactically correct and swallowed by the compiler without
complaint.
On the other hand, if you accidentally type "if (0 = i), the compiler
will emit a diagnostic and reject it.
So it is a very inexpensive method of catching a typing error on the
very first compile. This is not an extremely common error, but is one
which happens to everyone once in a while. And of course it doesn't
help when you are comparing two objects, but comparisons with a
constant are fairly frequent.
Some programmers consider it hideously ugly and refuse to ever use it.
I think it is useful and I use it. It works, and it saves time when
you do happen to make that typo.
--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++ http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html
Jack Klein wrote:
On Sun, 4 May 2008 22:40:28 -0400, "barcarolle r"
<ba*********@mu sic.netwrote in comp.lang.c++:
>Is it now common practice to use conditional statements like
if (0 == i)
if (-1 == i)
if (true == i)
if (5 == i)
over the more traditional statements like
if (i == 0)
if (i == -1)
if (i == true)
if (i == 5)
for all types of 'i' (PODs and classes)?
The reason for writing the constant first in an equality comparison is
quite simple. A fairly common typographical error is type only one
'=' once in a while when two are intended, and needed.
Consider the implications of accidentally typing:
if (i = 0)
...when you meant to type:
if (i == 0)
Assuming a built-in type, or even a class type having an assignment
operator accepting an int, then the first version, the type, is not
only always false, but it also destroys the existing value of 'i'. Yet
it is syntactically correct and swallowed by the compiler without
complaint.
On the other hand, if you accidentally type "if (0 = i), the compiler
will emit a diagnostic and reject it.
So it is a very inexpensive method of catching a typing error on the
very first compile. This is not an extremely common error, but is one
which happens to everyone once in a while. And of course it doesn't
help when you are comparing two objects, but comparisons with a
constant are fairly frequent.
Some programmers consider it hideously ugly and refuse to ever use it.
I think it is useful and I use it. It works, and it saves time when
you do happen to make that typo.
I agree, but my compiler warns me if an assignment is being made inside an
if statement. Otherwise I probably would use that format. But since it
does, I stick with the more traditional if ( variable == value )
--
Jim Langston ta*******@rocke tmail.com
"Jim Langston" <ta*******@rock etmail.comwrote in message
news:wM******** *******@newsfe0 5.lga...
Jack Klein wrote:
<...>
>The reason for writing the constant first in an equality comparison is
quite simple. A fairly common typographical error is type only one
'=' once in a while when two are intended, and needed.
Consider the implications of accidentally typing:
if (i = 0)
...when you meant to type:
if (i == 0)
Assuming a built-in type, or even a class type having an assignment
operator accepting an int, then the first version, the type, is not
only always false, but it also destroys the existing value of 'i'. Yet
it is syntactically correct and swallowed by the compiler without
complaint.
On the other hand, if you accidentally type "if (0 = i), the compiler
will emit a diagnostic and reject it.
So it is a very inexpensive method of catching a typing error on the
very first compile. This is not an extremely common error, but is one
which happens to everyone once in a while. And of course it doesn't
help when you are comparing two objects, but comparisons with a
constant are fairly frequent.
Some programmers consider it hideously ugly and refuse to ever use it.
I think it is useful and I use it. It works, and it saves time when
you do happen to make that typo.
I agree, but my compiler warns me if an assignment is being made inside an
if statement. Otherwise I probably would use that format. But since it
does, I stick with the more traditional if ( variable == value )
Of course to address the problem effectively one could simply *replace* the
offending operators:
#define IS_EQUAL_TO ==
#define INITIALISE_WITH =
#define PLUS +
#define OUTPUT <<
#define CONTENTS_OF *
#define POINTER *
#define ADDRESS_OF &
#include <iostream>
int main()
{
int x INITIALISE_WITH 1;
int POINTER px INITIALISE_WITH ADDRESS_OF x;
if ( CONTENTS_OF px PLUS 1 IS_EQUAL_TO 2){
std::cout OUTPUT "Who needs operators?\n";
}
}
regards
Andy Little
On May 5, 4:40 am, "barcarolle r" <barcarol...@mu sic.netwrote:
Is it now common practice to use conditional statements like
if (0 == i)
if (-1 == i)
if (true == i)
if (5 == i)
over the more traditional statements like
if (i == 0)
if (i == -1)
if (i == true)
if (i == 5)
for all types of 'i' (PODs and classes)?
No. First of all, you never compare with true or false. As for
the others, I'd say that it is generally universal practice to
put the constant to the right of the comparision operator. I
don't know where this practice originated, but it certainly
predates C++, and there's no reason to do otherwise in C++.
--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
James Kanze <ja*********@gm ail.comwrites:
On May 5, 4:40 am, "barcarolle r" <barcarol...@mu sic.netwrote:
>Is it now common practice to use conditional statements like
> if (0 == i)
if (-1 == i)
if (true == i)
if (5 == i)
>over the more traditional statements like
> if (i == 0)
if (i == -1)
if (i == true)
if (i == 5)
>for all types of 'i' (PODs and classes)?
No. First of all, you never compare with true or false. As for
the others, I'd say that it is generally universal practice to
put the constant to the right of the comparision operator. I
don't know where this practice originated, but it certainly
predates C++, and there's no reason to do otherwise in C++.
The reason is that if you have a normal keyboard, without rebound,
you'll type:
if (i = -1) ...
and then the compilers won't complain and will generate:
{ i=-1;
... }
On the other hand, if you write:
if (-1 = i) ...
since -1 is not a LHS, -1=i is invalid and the compilers will signal
an error.
However, I cannot say that's it's common practice.
I prefer to write if(i==-1)...
and I just insert a grep in my makefiles to catch any assignment in
if, while or do conditionals.
--
__Pascal Bourguignon__
On May 5, 3:28 pm, p...@informatim ago.com (Pascal J. Bourguignon)
wrote:
James Kanze <james.ka...@gm ail.comwrites:
On May 5, 4:40 am, "barcarolle r" <barcarol...@mu sic.netwrote:
Is it now common practice to use conditional statements like
if (0 == i)
if (-1 == i)
if (true == i)
if (5 == i)
over the more traditional statements like
if (i == 0)
if (i == -1)
if (i == true)
if (i == 5)
for all types of 'i' (PODs and classes)?
No. First of all, you never compare with true or false. As for
the others, I'd say that it is generally universal practice to
put the constant to the right of the comparision operator. I
don't know where this practice originated, but it certainly
predates C++, and there's no reason to do otherwise in C++.
The reason is that if you have a normal keyboard, without rebound,
you'll type:
if (i = -1) ...
and then the compilers won't complain and will generate:
{ i=-1;
... }
First, of course, I won't generally type that; I'll type:
if ( i == -1 ) ...
(with lot's of white space, so it's easy to see what each token
is). Second, if I do slip up, most compilers will warn, and of
course, the code will never get through code review, nor pass
any of the unit tests. So it's not really a big thing.
On the other hand, if you write:
if (-1 = i) ...
since -1 is not a LHS, -1=i is invalid and the compilers will
signal an error.
Which only works if you're comparing with a constant. On the
other hand, if I write:
if ( f() == x ) ...
rather than
if ( x == f() ) ...
I get the added check with the more natural form. So you force
an unnatural form to occasionally get the check, and more often
to not get it when you otherwise would.
However, I cannot say that's it's common practice.
I prefer to write if(i==-1)...
and I just insert a grep in my makefiles to catch any
assignment in if, while or do conditionals.
Automated code review:-). Definitely a good idea.
--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
On 5 touko, 16:19, James Kanze <james.ka...@gm ail.comwrote:
First of all, you never compare with true or false.
I'm doing that. What could go wrong?
Krice <pa****@mbnet.f iwrites:
On 5 touko, 16:19, James Kanze <james.ka...@gm ail.comwrote:
>First of all, you never compare with true or false.
I'm doing that. What could go wrong?
Well, with false, not much wrong, since false must be == !true, and
if(false){this; }else{that;} must evaluate that, we're about certain
that false == 0.
But for true, it's something else. It may be 1, -1, 0xff, or whatever
not 0.
But in any case, it's harder to read boolean expression when you add
equivalences with the constants.
Compare:
Is it true that it is false that you're not big?
if(true==(false ==(not(you->big())))){ fast();}
Are you big?
if(you->big()){ fast();}
Ok, even if you remove some == and some not, it's still harder to
understand the question:
Is it true that you're big?
if(true==you->big()){ fast();}
--
__Pascal Bourguignon__
On 2008-05-05 10:48:06 -0400, Krice <pa****@mbnet.f isaid:
On 5 touko, 16:19, James Kanze <james.ka...@gm ail.comwrote:
>First of all, you never compare with true or false.
I'm doing that. What could go wrong?
Not much. But what's the point? The compiler does it. And, more
important, where do you stop?
if (a)
if (a == true)
if ((a == true) == true)
if (((a == true) == true) == true)
--
Pete
Roundhouse Consulting, Ltd. ( www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
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