How to use ? and : in a program

[Michael Jack]

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement? Any
explanation will be appreciated.

<?
$x=32;
$y=80;
function gcd($a, $b)
{ return ($b>0)?gcd($b,$a%$b):$a;}
$val=gcd($x, $y);
print "The greatest common denominator of $x and $y is $val";
?>

This recursive program is used to find the greatest common denominator of 2
numbers.

TIA

[Erwin Moller]

Michael Jack wrote:

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement?
Any explanation will be appreciated.
Hi Michael,

It is just a shorthand notation for an if-then-else statement

eg:
$a = 10;
echo ( ($a<20) ? "$a is smaller then 20!" : "$a is not smaller then 20!");

is the same as:
$a = 10;
if ($a<20) {
echo "$a is smaller then 20!";
} else {
echo "$a is not smaller then 20!";
}

Regards,
Erwin Moller


<?
$x=32;
$y=80;
function gcd($a, $b)
{ return ($b>0)?gcd($b,$a%$b):$a;}
$val=gcd($x, $y);
print "The greatest common denominator of $x and $y is $val";
?>

This recursive program is used to find the greatest common denominator of
2 numbers.

TIA

[Michael Jack]

Many thanks.

"Erwin Moller"
<si******************************************@spam yourself.com> wrote in
message news:43***********************@news.xs4all.nl...

Michael Jack wrote:

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement?
Any explanation will be appreciated.

Hi Michael,

It is just a shorthand notation for an if-then-else statement

eg:
$a = 10;
echo ( ($a<20) ? "$a is smaller then 20!" : "$a is not smaller then 20!");

is the same as:
$a = 10;
if ($a<20) {
echo "$a is smaller then 20!";
} else {
echo "$a is not smaller then 20!";
}

Regards,
Erwin Moller

<?
$x=32;
$y=80;
function gcd($a, $b)
{ return ($b>0)?gcd($b,$a%$b):$a;}
$val=gcd($x, $y);
print "The greatest common denominator of $x and $y is $val";
?>

This recursive program is used to find the greatest common denominator of
2 numbers.

TIA

[Oli Filth]

Erwin Moller said the following on 11/10/2005 10:05:

Michael Jack wrote:

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement?
Any explanation will be appreciated.

Hi Michael,

It is just a shorthand notation for an if-then-else statement

Not quite. You couldn't use it for something like:

if (6 == $a)
{
for ($i = 0; $i < $a; ++i)
{
...
}
}
else
{
// Some other code
}
It's really a conditional assignment operator.

--
Oli

[Michael Jack]

Many thanks for the prompt reply.

Regards,

"Erwin Moller"
<si******************************************@spam yourself.com> wrote in
message news:43***********************@news.xs4all.nl...

Michael Jack wrote:

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement?
Any explanation will be appreciated.

Hi Michael,

It is just a shorthand notation for an if-then-else statement

eg:
$a = 10;
echo ( ($a<20) ? "$a is smaller then 20!" : "$a is not smaller then 20!");

is the same as:
$a = 10;
if ($a<20) {
echo "$a is smaller then 20!";
} else {
echo "$a is not smaller then 20!";
}

Regards,
Erwin Moller

<?
$x=32;
$y=80;
function gcd($a, $b)
{ return ($b>0)?gcd($b,$a%$b):$a;}
$val=gcd($x, $y);
print "The greatest common denominator of $x and $y is $val";
?>

This recursive program is used to find the greatest common denominator of
2 numbers.

TIA

[Jerry Sievers]

"Michael Jack" <mi*****@jack2005.com> writes:

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement? Any
explanation will be appreciated.

<?
$x=32;
$y=80;
function gcd($a, $b)
{ return ($b>0)?gcd($b,$a%$b):$a;}
$val=gcd($x, $y);
print "The greatest common denominator of $x and $y is $val";

You have stumbled on the ternary operator;

But the real reason for this is to obfuscate the program and confuse
everyone who reads it!

No kidding. I quit using ?: years ago and prefer the more verbose
if/then/else. Others may disagree.

HTH

--
-------------------------------------------------------------------------------
Jerry Sievers 305 854-3001 (home) WWW ECommerce Consultant
305 321-1144 (mobile http://www.JerrySievers.com/

[Erwin Moller]

Oli Filth wrote:

Erwin Moller said the following on 11/10/2005 10:05:

Michael Jack wrote:

Hi,

in the program below, what is the meaning/use of
the question mark (?gcd) and the colon (:$a) after the return statement?
Any explanation will be appreciated.

Hi Michael,

It is just a shorthand notation for an if-then-else statement

Not quite. You couldn't use it for something like:

if (6 == $a)
{
for ($i = 0; $i < $a; ++i)
{
...
}
}
else
{
// Some other code
}
It's really a conditional assignment operator.

True.
:-)

Regards,
Erwin Moller

In article <xY******************@newsfe6-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote:

It's really a conditional assignment operator.

But it isn't an assignment operator.

--
http://yosemitecampsites.com/

[Oli Filth]

el***@no.spam said the following on 11/10/2005 18:34:

In article <xY******************@newsfe6-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote:

It's really a conditional assignment operator.

But it isn't an assignment operator.

Good point.
--
Oli

[Erwin Moller]

Oli Filth wrote:

el***@no.spam said the following on 11/10/2005 18:34:

In article <xY******************@newsfe6-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote:

It's really a conditional assignment operator.

But it isn't an assignment operator.

Good point.

Slowly but surely we are getting there!
;-)

Regards,
Erwin Moller