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Rounding issue (ceil)

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Rounding issue (ceil) JavaScript Development forum discussing the use of JavaScript and its features as a powerful DOM manipulator. JavaScript is used in most websites to enrich the interface and enhance the user experience.

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  #1  
Old April 17th, 2007, 10:49 PM
phpscripter phpscripter is offline
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Rounding issue (ceil)
Hi could you please help me to get this going?

I have a particular rounding issue.
I need to determine whether or not a number has 0's as decimal places and depending on that either 'ceil' or not.

An example:
Code:
pre_tax_t = totaldue_*0.125;   // the total of a shopping basket * 12.5% tax
tax_t = pre_tax_t.toFixed(3);   // this limits the decimal places (3)


Now, if the value of tax_t is: 39.131
I'd need to round up (ceil) the third decimal place, which should give something like this: 39.14

but if the value of tax_t is: 20.100
I don't want to 'ceil' and basically leave it as it is because "ceil' would actually return 20.11, which is wrong.

Any help is very much appreciated.

Cheers
Jan
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  #2  
Old April 18th, 2007, 02:40 AM
mecanicu mecanicu is offline
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Workaround
Hi Jan,
Here is how you can modify the Decimals function so it will return just the effective number of decimals. I mean 1.210 has only two decimals that really count.

JavaScript Code:
Original - JavaScript Code 
  1. function Decimals(x, dec_sep)
  2. {
  3.     var tmp=new String();
  4.     tmp=x;
  5.     if (tmp.indexOf(dec_sep)>-1)
  6.     {
  7.         len = tmp.length;
  8.         ret_val = len-tmp.indexOf(dec_sep)-1;
  9.         while (tmp.charAt(--len)=="0")
  10.             ret_val--;
  11.     }
  12.     else
  13.         ret_val = 0;
  14.     return ret_val;
  15. }

all the best
mecanicu
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  #3  
Old April 18th, 2007, 03:06 AM
phpscripter phpscripter is offline
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Quote:
Originally Posted by mecanicu
Hi Jan,
Here is how you can modify the Decimals function so it will return just the effective number of decimals. I mean 1.210 has only two decimals that really count.

JavaScript Code:
Original - JavaScript Code 
  1. function Decimals(x, dec_sep)
  2. {
  3.     var tmp=new String();
  4.     tmp=x;
  5.     if (tmp.indexOf(dec_sep)>-1)
  6.     {
  7.         len = tmp.length;
  8.         ret_val = len-tmp.indexOf(dec_sep)-1;
  9.         while (tmp.charAt(--len)=="0")
  10.             ret_val--;
  11.     }
  12.     else
  13.         ret_val = 0;
  14.     return ret_val;
  15. }

all the best
mecanicu


Thank you for your help but:
When I call that fucntion like this :
Code:
test = Decimals(number,decimal places)

I get nothing.

Something wrong?

Cheers
Jan
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  #4  
Old April 18th, 2007, 04:47 AM
mecanicu mecanicu is offline
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Yes. You are supposed to ask
test = Decimals(number, ".");
Some countries use "," as decimal separator so this is the `internationalization` part.
The result, in test, will be the number of effective decimals
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  #5  
Old April 18th, 2007, 09:44 PM
phpscripter phpscripter is offline
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Quote:
Originally Posted by mecanicu
Yes. You are supposed to ask
test = Decimals(number, ".");
Some countries use "," as decimal separator so this is the `internationalization` part.
The result, in test, will be the number of effective decimals


Well, thank you for that.
I had to slightly modify that to make it work. Apparently 'number' has to be a STRING. It only works by converting the 'number' to a STRING. The function "toString" is quite handy for that purpose.
Code:
pre_tax_t = totaldue_*0.125; // get the tax
test = Decimals(pre_tax_t.toString(), '.');

The result, in test, will now be the number of effective decimals.

Is it possible to filter the result in test for a 0. Or to put it differently, how can I detect whether there are <3 decimals or whether the third decimal a 0.

I'd like to illustrate myissue by means of an example:

Given the following figures:
totaldue_ -> 313.05 // total of a shopping basket
pre_tax_t = totaldue_*0.125; // get the tax
that totals to:
pre_tax_t -> 39.13125

If the third decimal place is >0, I need to ceil to 2 decimals
I can do this with (which is fine):
Code:
pre_tax_t -> 39.13125
test_a = Math.ceil( pre_tax_t*100 )/100;
// test_a = 39.14



The problem starts with (for example) the following given figures:
totaldue_ -> 160.80
pre_tax_t = totaldue_*0.125;
that totals to:
pre_tax_t -> 20.1

If there is no third decimal or if the third decimal is a 0, I need to rather do nothing or floor, because with 'ceil I'd get this (which is wrong:
Code:
pre_tax_t -> 20.1
test_a = Math.ceil( pre_tax_t*100 )/100;
// test_a = 20.11


This would be ok:
Code:
pre_tax_t -> 20.1
test_b = Math.floor( pre_tax_t*100 )/100
20.1


Can I somehow use your code to get this going?

Cheers
Jan
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  #6  
Old April 19th, 2007, 01:00 AM
phpscripter phpscripter is offline
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Fixed
Thank you for your help.
That issue has been fixed with some thought-provoking impulse from you guys.

Well here ist the code, certainly a bit different because I use that javascript part as a php-embedded one. Please have a closer look at Line 8, because thats the juicy part. To floor the result in Line 12 in order to get the right result is actually a bit dowdy, but I can live with it.
Code:
Line 1		echo "pre_tax_t = totaldue_*0.125;\n";   // get the amount tax	
Line 2		echo "tax_t  = pre_tax_t.toFixed(3);\n"; // fix to 3 decimals and use for ceil
Line 3		echo "tax_l  = pre_tax_t.toFixed(2);\n"; // fix to 2 decimals and do nothing
				
						
Line 4		echo "tk = tax_t*100;\n"; 
Line 5		echo "tk = tk.toFixed(2);\n"; 
				
Line 6		echo "tfl = Math.floor( tax_t*100 );\n"; 
Line 7		echo "tfl = tfl.toFixed(2);\n"; 
Line 8		echo "tax_t = (tk != tfl) ? (Math.ceil( tax_t*100 ) ) / 100 : tax_l;\n";// Line 3
								
		
Line 9		echo "pre_tax_ts = ship_cost_*0.125;\n";
Line 10		echo "tax_s = pre_tax_ts.toFixed(3);\n";
Line 11		echo "tax_s = Math.ceil(tax_s*100 )/100;\n"; 
				
						
				
Line 12		echo "tax = ((Math.floor(tax_t*100))/100)+((Math.floor(tax_s*100))/100);\n";
Line 13		echo "totaldue_ = totaldue_+ship_cost_+tax;\n";


Cheers
Jan
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