round numbers with a caveat?

[Lance Hoffmeyer]

Hey all,

I want to round numbers with one decimal place.
I know one can round in this manner:

sub round {
my($value) = shift;
return int($value + .5);
}


What I now need to add to this if that if a number is exactly
??.5 and is an even number then round down (i.e. 22.5 = 22)
and if a number is odd and ??.5 then round up (i.e. 21.5 = 22).

How can I test whether a number is even or odd?

sub round {
if ($value = "??.5 and even){ $value = $value - .1};
if ($value = "??.5 and odd"){ $value = $value + .1};

my($value) = shift;
return int($value + .5);
}

 

[watsonbladd]

Hey all,

I want to round numbers with one decimal place.
I know one can round in this manner:

sub round {
my($value) = shift;
return int($value + .5);

}

What I now need to add to this if that if a number is exactly
??.5 and is an even number then round down (i.e. 22.5 = 22)
and if a number is odd and ??.5 then round up (i.e. 21.5 = 22).

How can I test whether a number is even or odd?

sub round {
if ($value = "??.5 and even){ $value = $value - .1};
if ($value = "??.5 and odd"){ $value = $value + .1};

my($value) = shift;
return int($value + .5);

}

$int%2 is 0 for even, 1 for odd.

 

[anno4000]

Hey all,

I want to round numbers with one decimal place.
I know one can round in this manner:

sub round {
my($value) = shift;
return int($value + .5);
}

That works for positive values, but not for negative ones.
The normal way to round numbers in Perl is sprintf:

sprintf '%.0f', $value;

rounds to an integer. See also "perldoc -q round".

What I now need to add to this if that if a number is exactly
??.5 and is an even number then round down (i.e. 22.5 = 22)
and if a number is odd and ??.5 then round up (i.e. 21.5 = 22).

That is the standard and sprintf works this way.

for my $x ( -1.5, -0.5, 0.5, 1.5, 2.5, 3.5 ) {
my $y = sprintf'%.0f', $x;
print "$x -> $y\n";
}

How can I test whether a number is even or odd?

You don't have to for the purpose of rounding.

Besides taking the number mod 2, which has been suggested, you
can use the binary representation and test the least significant
bit:

my $parity = $y & 1 ? 'odd' : 'even';

Anno