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digitalmars.D.bugs - Bool bugs

reply "Kris" <fu bar.com> writes:
I really don't wish to open up the old Bool wounds, but the following should 
surely be considered a bug.

~~~~~~~~~~~~~~
module foo;

bool x, y;


bool test ()
{
        return x == y;
}

bool test1 ()
{
        return x == false;
}

bool test2 ()
{
        return y is true;
}
~~~~~~~~~~~~~~

Compiled with -w, we get the following:

warning - foo.d(8): implicit conversion of expression (cast(int)(x) == 
cast(int)(y)) of type int to bit can cause loss of data
warning - foo.d(13): implicit conversion of expression (cast(int)(x) == 0) 
of type int to bit can cause loss of data
warning - foo.d(18): implicit conversion of expression (cast(int)(y) is 1) 
of type int to bit can cause loss of data


This is just plain daft. And it's just the kind of thing to contribute to a 
perception that D is "unpolished" and "unprofessional".



To eliminate such warnings (which one should strive to do), one has to 
resort to comedy:

~~~~~~~~~~~~~~
module foo;

bool x, y;


bool test ()
{
        return cast(bool) (x == y);
}

bool test1 ()
{
        return cast(bool) (x == false);
}

bool test2 ()
{
        return cast(bool) (y is true);
}
~~~~~~~~~~~~~~

That is: cast boolean expressions, using only boolean operands, to boolean 
expressions.
Dec 30 2005
next sibling parent reply "Derek Parnell" <derek psych.ward> writes:
On Sat, 31 Dec 2005 10:16:04 +1100, Kris <fu bar.com> wrote:


 I really don't wish to open up the old Bool wounds, but the following  
 should
 surely be considered a bug.



 That is: cast boolean expressions, using only boolean operands, to  
 boolean
 expressions.



Doesn't this happen because comparision expressions return an int rather  
than a bool (aka bit)? I'm sure this is done for performance reasons  
rather than good language reasons. Another trade off for those who prefer  
speed over clarity.

-- 
Derek Parnell
Melbourne, Australia
Dec 30 2005
parent reply Ivan Senji <ivan.senji_REMOVE_ _THIS__gmail.com> writes:
Derek Parnell wrote:

 On Sat, 31 Dec 2005 10:16:04 +1100, Kris <fu bar.com> wrote:
 

 I really don't wish to open up the old Bool wounds, but the following  
 should
 surely be considered a bug.


 
 

 That is: cast boolean expressions, using only boolean operands, to  
 boolean
 expressions.


 
 
 
 Doesn't this happen because comparision expressions return an int 
 rather  than a bool (aka bit)? I'm sure this is done for performance 
 reasons  rather than good language reasons. Another trade off for those 
 who prefer  speed over clarity.
 


No performance would be lost and clarity would be increased if int sized 
real boolean type would be added having nothing in common with bit.
Dec 30 2005
parent reply "Derek Parnell" <derek psych.ward> writes:
On Sat, 31 Dec 2005 10:28:52 +1100, Ivan Senji  
<ivan.senji_REMOVE_ _THIS__gmail.com> wrote:


 Derek Parnell wrote:

 On Sat, 31 Dec 2005 10:16:04 +1100, Kris <fu bar.com> wrote:


 I really don't wish to open up the old Bool wounds, but the following   
 should
 surely be considered a bug.



 That is: cast boolean expressions, using only boolean operands, to   
 boolean
 expressions.


    Doesn't this happen because comparision expressions return an int  
 rather  than a bool (aka bit)? I'm sure this is done for performance  
 reasons  rather than good language reasons. Another trade off for those  
 who prefer  speed over clarity.


 No performance would be lost and clarity would be increased if int sized  
 real boolean type would be added having nothing in common with bit.


Agreed. It's the "alias bit bool" that is the problem here. If bool was an  
int then this wouldn't happen so long as the compiler treated all non-zero  
values of a bool to mean 'true' and only used zero value to mean 'false'.

-- 
Derek Parnell
Melbourne, Australia
Dec 30 2005
parent Manfred Nowak <svv1999 hotmail.com> writes:
Derek Parnell wrote:

[...]

 If bool was an  int then this wouldn't happen so long as the
 compiler treated all non-zero  values of a bool to mean 'true'
 and only used zero value to mean 'false'. 


... until someone comes up with a posting saying like:


Look at:

code:
bool x, y;
// some code omitted
writefln( x, y, x & y); 

output:
truetruefalse

How comes? This surely must be a bug.

-manfred
Dec 30 2005
prev sibling parent Ivan Senji <ivan.senji_REMOVE_ _THIS__gmail.com> writes:
Kris wrote:
//smart and valid comments/questions removed

Oh Kris, what could it be that makes you think that boolean expressions 
should be of boolean type. What a strange idea. :)

Siriusly: It would be the best present for new year if Walter just 
simply added boolean type to D without touching bit.
Dec 30 2005