int to float to float to int

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int to float to float to int

 
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  #1
Jul 27th, 2009
i need help
I need to display
Example
23.4
and display 23 and .4

how do i do this?

so i need to convert a decimal into fraction
like this
http://www.cimt.plymouth.ac.uk/proje...7/bk7_17i1.htm
i need to display 4 and 0.276
Last edited by yasaswyg; Jul 27th, 2009 at 4:48 pm. Reason: found out
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Re: int to float to float to int

 
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Jul 27th, 2009
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I need to display
Example
23.4
and display 23 and .4
One easy way is with the type system. When you cast a floating point value it cuts off the precision. If you subtract that result from the original, you get the precision:
c Syntax (Toggle Plain Text) 
  1. double d = 23.4;
  2. double w = (int)d; /* w == 23.0 */
  3. double p = d - w; /* p == 0.4 */
Last edited by Tom Gunn; Jul 27th, 2009 at 5:01 pm.
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Re: int to float to float to int

 
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  #3
Jul 27th, 2009
just do type casting
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Re: int to float to float to int

 
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  #4
Jul 27th, 2009
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Originally Posted by Tom Gunn View Post
One easy way is with the type system. When you cast a floating point value it cuts off the precision. If you subtract that result from the original, you get the precision:
c Syntax (Toggle Plain Text) 
  1. double d = 23.4;
  2. double w = (int)d; /* w == 23.0 */
  3. double p = d - w; /* p == 0.4 */
DAMN thats common sense
THanks alot.
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Re: int to float to float to int

 
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Jul 27th, 2009
idk what that means
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Re: int to float to float to int

 
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Jul 28th, 2009
you dont know what what means? casting? start from the beginning of Tom Gunns code snippet:

'd' is a double (floating point) variable containing 23.4.

'w' is a double variable set to the value of 'd' once 'd' is casted as an integer. (see where 'd' is casted as an integer by the use of 'int' type in parentheses.) now 'w' contains the whole value 23.0 with no fractional part.

'p' is another double variable that is the value of the difference between 'd' and 'w'... since 'd' is 23.4 and 'w' is 23.0, the difference is 0.4, and this fractional part is assigned to 'p'

now 'd' still contains the original decimal value (23.4), and 'w' contains the whole number (23) and 'p' contains the fractional part (0.4)


.
Last edited by jephthah; Jul 28th, 2009 at 12:32 am. Reason: .
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Re: int to float to float to int

 
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Jul 28th, 2009
im sorry but i havent learned that in my class

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Originally Posted by jephthah View Post
you dont know what what means? casting? start from the beginning of Tom Gunns code snippet:

'd' is a double (floating point) variable containing 23.4.

'w' is a double variable set to the value of 'd' once 'd' is casted as an integer. (see where 'd' is casted as an integer by the use of 'int' type in parentheses.) now 'w' contains the whole value 23.0 with no fractional part.

'p' is another double variable that is the value of the difference between 'd' and 'w'... since 'd' is 23.4 and 'w' is 23.0, the difference is 0.4, and this fractional part is assigned to 'p'

now 'd' still contains the original decimal value (23.4), and 'w' contains the whole number (23) and 'p' contains the fractional part (0.4)


.
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Re: int to float to float to int

 
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Aug 17th, 2009
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Originally Posted by yasaswyg View Post
i need help
I need to display
Example
23.4
and display 23 and .4

how do i do this?
I'm trying to do something similar, only instead of displaying the numbers, I need to store them. I need to store both as ints, though.

The problem I'm running into is coming up with a generic algorithm for storing the 0.4 part as just 4. I don't know how many digits the number will be every time, so I can't use a constant multiplier to move the decimal.

This is what I've come up with so far:

float n = 123.456;

// 123
int nw = (int)n;

// 456
int nf = (int)( ( n - nw ) * pow( 10, ??? ) );

I would much prefer a mathematical solution, but I would be willing to convert to a string and back, if that's the only way.
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Re: int to float to float to int

 
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  #9
Aug 17th, 2009
Floating type does not have fixed precision.
and if you enter
123.456
try to print that variable - you'll get something like that
123.455969706597869578956
So you have to convert its number into string and parse it.

Or choose precision and your code will be like that
cpp Syntax (Toggle Plain Text) 
  1. int prec = 5;
  2. int nf = (int)( ( n - nw ) * pow( 10, prec ) );
But this method is not precise.
Last edited by Protuberance; Aug 17th, 2009 at 2:06 pm.
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Re: int to float to float to int

 
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  #10
Aug 17th, 2009
Is there a better (faster) way to convert than sprintf() that you know of? I'm working in a real-time system, and sprintf() is computationally expensive.
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