update: C programming help (log function)

[Omegachi]

// hi guys, my math.h file don't work and i need to use a log() function. can someone show me the function to do log base 2?

new question, how do you break out of main()?

break; don't work.

 

[emmpee]

so you want to do it without using any math.h routines?

 

[ThisIsMatt]

why doesn't your math.h work? lol

 

[br0wn]

Shift right by 23, then subtract 127..

This works for 32 bit IEEE float.


Try the following code:

input: float v
output: int c ------- log2(v)

c = ((*(int *) &v) >> 23) - 127;

 

[Omegachi]

yea.... trying to make a double log( int n) file. without math.h

 

[dighn]

you can probably approximate it with a taylor series expansion. google it

but just wondering how is math.h not working?

 

[MacBaine]

make sure you remember your -lm compile flag! 😉

 

[cchen]

Originally posted by: Omegachi
yea.... trying to make a double log( int n) file. without math.h

how can math.h not work? are you compiling with gcc? might need a -lm flag at the end

 

[Omegachi]

can someone find me the code......

 

[br0wn]

try the code i posted in the third post.