anything whcih can be done with ternary but not with if else

[gupta.keshav]

HI,
Is there any situation which can be handled by ternary operator but
not with if else blocks?
Thanks
Keshav

[Rolf Magnus]

gu**********@gmail.com wrote:

HI,
Is there any situation which can be handled by ternary operator but
not with if else blocks?

class Foo
{
public:
Foo(bool b)
: x_(b ? 42 : 7)
{
}
private:
const int x_;
};

[mlimber]

Rolf Magnus wrote:

gu**********@gmail.com wrote:

HI,
Is there any situation which can be handled by ternary operator but
not with if else blocks?

class Foo
{
public:
Foo(bool b)
: x_(b ? 42 : 7)
{
}
private:
const int x_;
};

And conditionally assigning constants in general. Compare:

void Foo( const bool b )
{
const int i = b ? 1 : 2;
// ...
}

void Bar( const bool b )
{
// i cannot be const
int i = 0;
if( b )
{
i = 1;
}
else
{
i = 2;
}
// ...
}

Cheers! --M

[John Carson]

<gu**********@gmail.com> wrote in message
news:11*********************@g14g2000cwa.googlegro ups.com

HI,
Is there any situation which can be handled by ternary operator but
not with if else blocks?
Thanks
Keshav

bool b;
int x, y;

// stuff setting b, x and y

int & ref = b ? x, y;

Note that you can do

if(b)
int & ref = x;
else
int & ref = y;

but the scope of the reference is limited to the body of the if-else
conditions. You can't get around this by declaring the reference before the
if statement because a reference must be initialised at its point of
declaration.

--
John Carson

[shailendra]

what if I'm doing this?

int const * foo( const bool b )
{
static int i = 0;

if( b )
{
i = 1;
}
else
{
i = 2;
}
return &i;
}

[Fraser Ross]

int const * foo( const bool b )
{
static int i;
return &(i=b ? 1 : 2);
}
This is the equivalent using the ternary operator making the function as
short as possible. This doesn't give an example that the OP is looking
for.

Fraser.

[mlimber]

shailendra wrote:

what if I'm doing this?

int const * foo( const bool b )
{
static int i = 0;

if( b )
{
i = 1;
}
else
{
i = 2;
}
return &i;
}

It should work fine, and you could use the ternary operator, though not
on the initialization of the static:

int const* foo( const bool b )
{
static int i = 0; // Only executed once
i = b ? 1 : 2; // Executed each time foo is called
return &i;
}

Cheers! --M

[shailendra]

My reply was to the examples given by "mlimber" that, there is a way to
substitute his/her idea --

So given example is wrong, coz this isn't the only situatuation where
ternery can be applied. So we better find some good situation only for
ternery.

Frankly speaking, I dont think, there is any!!

[Jay Nabonne]

On Mon, 17 Oct 2005 05:49:18 -0700, gupta.keshav wrote:

HI,
Is there any situation which can be handled by ternary operator but
not with if else blocks?

I'm not sure there is such a case *if* you're allowed to put the if/else
in a separately called function.

e.g.

class Foo
{
public:
Foo(bool b)
: x_(getit(b))
{
}

int getit(bool b)
{
if (b)
return 42;
else
return 7;
}
private:
const int x_;
};

- Jay

[Mike Smith]

shailendra wrote:

My reply was to the examples given by "mlimber" that, there is a way to
substitute his/her idea --

So given example is wrong, coz this isn't the only situatuation where
ternery can be applied. So we better find some good situation only for
ternery.

Frankly speaking, I dont think, there is any!!

One has already been given.

--
Mike Smith

[Ali Çehreli]

<gu**********@gmail.com> wrote in message
news:11*********************@g14g2000cwa.googlegro ups.com...

Is there any situation which can be handled by ternary operator but
not with if else blocks?

if-else requires assignability. Anything that doesn't support assignment
cannot be used with if-else. In addition to the already provided constructor
initialization list, three more that I can think of:
1) A class that doesn't define operator=:

Class UnAssignable{ /* ... */ };

/* copy construction */
UnAssignable object = condition ? first : second;
2) Initializing a reference:

Class & reference = condition ? first : second;
3) Initializing a constant:

SomeType const object = condition ? first : second;

Ali

[persenaama]

You aren't replacing the ternary operator with if-else block but with a
function call with if-else block inside it. There's a subtle
difference, I think. A good suggestion, just happened to think, "wait
just a minute...!"

[Old Wolf]

mlimber wrote:

Rolf Magnus wrote:

gu**********@gmail.com wrote:

Is there any situation which can be handled by ternary operator
but not with if else blocks?

class Foo
{
public:
Foo(bool b) : x_(b ? 42 : 7) { }
private:
const int x_;
};

And conditionally assigning constants in general. Compare:

void Foo( const bool b )
{
const int i = b ? 1 : 2;
// ...
}

In this case it can be done with if...else:
void Foo( const bool b )
{
int i_;
if (b)
i_ = 1;
else
i_ = 2;
const int i = i_;
}

[Old Wolf]

Rolf Magnus wrote:

gu**********@gmail.com wrote:

Is there any situation which can be handled by ternary operator but
not with if else blocks?

class Foo
{
public:
Foo(bool b)
: x_(b ? 42 : 7)
{
}
private:
const int x_;
};

Note that this doesn't imply that ?: adds any new functionality
to the language; (b ? 42 : 7) is equivalent to (b * 35 + 7).

However I can't think of a replacment for (b ? foo() : bar()) offhand.

[gupta.keshav]

wht can be done is

bool b;
int x,y,z;
if (b) z= x; else z = y;
int &i = z;

[Greg Comeau]

What can also be done with ternary is it can be put
into a comma operator list, perhaps as part of a macro
--
Greg Comeau / Celebrating 20 years of Comeauity!
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?

[Rolf Magnus]

Greg Comeau wrote:

What can also be done with ternary is it can be put
into a comma operator list, perhaps as part of a macro

And it can be used in template arguments.

[John Carson]

<gu**********@gmail.com> wrote in message
news:11**********************@g44g2000cwa.googlegr oups.com

wht can be done is

bool b;
int x,y,z;
if (b) z= x; else z = y;
int &i = z;

That is not equivalent to

int &i = b ? x, y;

Suppose that the code is followed by:

i = 6;

With my code, either x or y will become 6. With your code, x and y are not
affected; the change is to z.
--
John Carson

[ben]

Old Wolf wrote:

Rolf Magnus wrote:

gu**********@gmail.com wrote:

Is there any situation which can be handled by ternary operator but
not with if else blocks?

class Foo
{
public:
Foo(bool b)
: x_(b ? 42 : 7)
{
}
private:
const int x_;
};

Note that this doesn't imply that ?: adds any new functionality
to the language; (b ? 42 : 7) is equivalent to (b * 35 + 7).

However I can't think of a replacment for (b ? foo() : bar()) offhand.

int f(bool b)
{
if (b) return foo();
else return bar();
}

class Foo
{
public;
Foo(bool b)
: x_(f(b))

.....

ben

[Jay Nabonne]

On Mon, 17 Oct 2005 13:26:31 -0700, persenaama wrote:

You aren't replacing the ternary operator with if-else block but with a
function call with if-else block inside it. There's a subtle
difference, I think. A good suggestion, just happened to think, "wait
just a minute...!"

You're quite right. I mostly mentioned it because, believe it or not, I
have seen coding guidelines that forbid the use of the ternary operator!
So knowing how to live without it can be useful (though I wouldn't want to).

- Jay

[shailendra]

Ali Çehreli wrote:

<gu**********@gmail.com> wrote in message
news:11*********************@g14g2000cwa.googlegro ups.com...

Is there any situation which can be handled by ternary operator but
not with if else blocks?

if-else requires assignability. Anything that doesn't support assignment
cannot be used with if-else. In addition to the already provided constructor
initialization list, three more that I can think of:
1) A class that doesn't define operator=:

Class UnAssignable{ /* ... */ };

/* copy construction */
UnAssignable object = condition ? first : second;
2) Initializing a reference:

Class & reference = condition ? first : second;
3) Initializing a constant:

SomeType const object = condition ? first : second;

Ali

I don't think overloading of ternary operator is possible in C++

[Ali Çehreli]

"shailendra" <su********@gmail.com> wrote in message
news:11*********************@g44g2000cwa.googlegro ups.com...

Ali Çehreli wrote:

<gu**********@gmail.com> wrote in message
news:11*********************@g14g2000cwa.googlegro ups.com...

Is there any situation which can be handled by ternary operator but
not with if else blocks?

if-else requires assignability. Anything that doesn't support assignment
cannot be used with if-else. In addition to the already provided
constructor
initialization list, three more that I can think of:
1) A class that doesn't define operator=:

Class UnAssignable{ /* ... */ };

/* copy construction */
UnAssignable object = condition ? first : second;
2) Initializing a reference:

Class & reference = condition ? first : second;
3) Initializing a constant:

SomeType const object = condition ? first : second;

Ali

I don't think overloading of ternary operator is possible in C++

Did you reply to my message by mistake? The reason I am asking is that I
can't understand what part you may be referring to. (The lack of o period at
the end of your sentence makes me believe that you really sent it by
mistake, at least prematurely.)

Maybe you thought that the pairs of first/second above were the same objects
in all three cases? If so, no, I didn't mean them to be so; think of each
pair as being defined separately in each case.

Even if I did mean to use the same first and second in all three cases, it
would still work, provided a suitable relationship (inheritance, constructor
parameter, existence of type conversion operators, etc.) among UnAssignable,
Class, SomeType, and the type used for first and second.

Ali

[Thomas J. Gritzan]

John Carson schrieb:

bool b;
int x, y;

// stuff setting b, x and y

int & ref = b ? x, y;

int *p;
if (b)
p = &x;
else
p = &y;

int &ref2 = *p;

Thomas

[John Carson]

"Thomas J. Gritzan" <Ph*************@gmx.de> wrote in message
news:dj**********@newsreader3.netcologne.de

John Carson schrieb:

bool b;
int x, y;

// stuff setting b, x and y

int & ref = b ? x, y;

int *p;
if (b)
p = &x;
else
p = &y;

int &ref2 = *p;

Thomas

Yes, a nice workaround (albeit one that comes at the cost of an extra
variable and extra assignment).

--
John Carson

[shailendra]

Sorry Ali, yes it was a mistake