I 'm trying to read and understand code for calculating FFT, I'm having problems with understanding this part:
but I don't know what 1<<m means?Code:m = int(log(Len)/log(2.0)); int Radix2 = 1 << m; // find nearest radix-2 length if (Radix2 != Len) { return(-1); }
Thanks!
check this out http://faq.cprogramming.com/cgi-bin/...&id=1073086407
>but I don't know what 1<<m means?
It means to shift the binary value of 1 to the left by m bits and fill the vacated bits with 0. Assuming 8 bits for simplicity, here is the progression of m being 0 to 6:
Notice the pattern? Apply that to the rest of the algorithm and see what you come up with.Code:1 == 0000001 m = 0: 0000001 m = 1: 0000010 m = 2: 0000100 m = 3: 0001000 m = 4: 0010000 m = 5: 0100000 m = 6: 1000000
My best code is written with the delete key.
what is this int(expr) function?
did you mean to type (int) expr ?
int(expression) is another form of casting. While I haven't seen it in C I have seen it in C++
Agree with Prelude;
Also, when shifting to the left you are actually multiplying by a power of 2 each time.
Notice the pattern Prelude spelled out.
Mr. C: Author and Instructor
>While I haven't seen it in C I have seen it in C++
That's because it isn't legal C.
My best code is written with the delete key.
That would explain why I hadn't seen it in C before
