rounding a value to nearest 1/2

[calan]

Does anyone have a function that will round a number to 0 or .5?

I have a form where I'm entering a number in inches. I need to round it to
the nearest 1/2 inch (onChange).

The split will be on increments of .25

22.24 = 22.0
22.25 = 22.5
22.52 = 22.5
22.74 = 22.5
22.751 = 23.0

TIA!

[Dr Clue]

Albert Grennock wrote:

"calan" <no**@nospam.co m> wrote in message

Does anyone have a function that will round a number to 0 or .5?

<snip> I don't really 'do' java but here is how I would do it in general terms.
Using C type terms.

Actually , we are speaking of "javascript " not "java". The distinction
is rather important.
Convert the number into a string eg "23.24", then take the last to
digits of the string eg "24".

Then all you have to do is say
if the string is less then "25" the result is "00"
else if the string is less then "75" the result is "50"
else the result is "00" (but remember to add one to the over all result).

Then convert back to a floating point number, adding 1 is necessary.

It will be much quicker than doing any floating point arithmetic
which is also likely to be inaccurate due to rounding problems.
Anyway its pretty simple and avoids things like getting
2.9999999999999 999999 rather than 3.0

Considering the OP's ( orignal poster's ) application , what
improvement does all that kinetic energy give us over
the common solution several of us gave as variations of the line below?

Math.round((22. 25*2))/2)

--
--.
--=<> Dr. Clue (A.K.A. Ian A. Storms) <>=-- C++,HTML, CSS,Javascript
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[Christopher Benson-Manica]

Albert Grennock <[e-mail] > wrote:

(OP has not reach my server, so I am piggybacking. Apologies.)

"calan" <no**@nospam.co m> wrote in message
news:og******** *********@newss vr12.news.prodi gy.com...

Does anyone have a function that will round a number to 0 or .5?

function half_round( num ) {
var fraction_part=M ath.floor( num*100 )%100;
var int_part=Math.f loor( num );
if( fraction_part < 25 ) {
return int_part;
}
else if( fraction_part < 75 ) {
return int_part+0.5;
}
return int_part+1;
}

(assuming, of course, you've played nicely and passed a number)
It will be much quicker than doing any floating point arithmetic
which is also likely to be inaccurate due to rounding problems.
Anyway its pretty simple and avoids things like getting
2.9999999999999 999999 rather than 3.0

I disagree.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Christopher Benson-Manica]

Dr Clue <ia*********@mi ndspring.com> wrote:

Considering the OP's ( orignal poster's ) application , what
improvement does all that kinetic energy give us over
the common solution several of us gave as variations of the line below?
I haven't seen "several", but I do wish I had seen your post before I
posted my version (although it's still better IMO than using the
string idea). Oy.
Math.round((22. 25*2))/2)

The only point I would raise is that this deserves a line of
documentation (although admittedly I have written much obtuse
JavaScript and omitted needed documentation).

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Dr Clue]

Christopher Benson-Manica wrote:

Dr Clue <ia*********@mi ndspring.com> wrote:

Considering the OP's ( orignal poster's ) application , what
improvement does all that kinetic energy give us over
the common solution several of us gave as variations of the line below?

I haven't seen "several", but I do wish I had seen your post before I
posted my version (although it's still better IMO than using the
string idea). Oy.

Math.round((2 2.25*2))/2)

The only point I would raise is that this deserves a line of
documentation (although admittedly I have written much obtuse
JavaScript and omitted needed documentation).

Your correct, but the sub-title of that message was "read the thread" :)
Thus the intentionally obtuse reference.

I simply copied that line from my other message , whose context
makes the thing clear.There was another respondent that gave a full
function body as well using the same logic.

I find a response like the one I gave to be far better than yelling
at them, as it might make them curious enough to RIFF.

--
--.
--=<> Dr. Clue (A.K.A. Ian A. Storms) <>=-- C++,HTML, CSS,Javascript
--=<> http://resume.drclue.net <>=-- AJAX, SOAP, XML, HTTP
--=<> http://www.drclue.net <>=-- SERVLETS,TCP/IP, SQL
--.

[Albert Grennock]

"Christophe r Benson-Manica" <at***@nospam.c yberspace.org> wrote in message
news:dg******** **@chessie.cirr .com...

Albert Grennock <[e-mail] > wrote:

(OP has not reach my server, so I am piggybacking. Apologies.)

"calan" <no**@nospam.co m> wrote in message
news:og******** *********@newss vr12.news.prodi gy.com...

Does anyone have a function that will round a number to 0 or .5?

function half_round( num ) {
var fraction_part=M ath.floor( num*100 )%100;
var int_part=Math.f loor( num );
if( fraction_part < 25 ) {
return int_part;
}
else if( fraction_part < 75 ) {
return int_part+0.5;
}
return int_part+1;
}

(assuming, of course, you've played nicely and passed a number)

It will be much quicker than doing any floating point arithmetic
which is also likely to be inaccurate due to rounding problems.
Anyway its pretty simple and avoids things like getting
2.9999999999999 999999 rather than 3.0

I disagree.

Maybe but my method requires no knowledge of libary functions or whatever.
and probably runs faster.
--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.