sin() function output range in ISO/IEC 9899:1999(E) (OS X man page says is based this)? i think
it is -1 - 1... but when made code which multiples result 32767
i get bigger numbers than 32767... for example if 32000 my waveform distorts.
i need values beetween -32767 - 32767.
Last edited by Vanhapolle; 12-08-2013 at 06:45 PM. Reason: I fixed function name i cannot fix title anyway at least i dont know how.
An example of the code may help clarify the question.
I'm assuming you mean sin, and yes that will be between -1 and 1. I'm a bit worried that you think 32000 is bigger than 32767 though.
If you don't ask clear questions, you won't get clear answers.
There is no such thing as a son() function in the C standard that produces a value between -1 and 1. There is a sin() function.
Without knowing what your code is doing, it is impossible to explain why it is producing values outside the range you expect.
Computers are more pedantic than people. If your code is wrong, they will obey the code in their own manner, regardless of what you expect.
and i want add this typing mistake hard found becouse somehow i read my own text i dont see mistakes. Which comes many times form this keyboard which choiced becouse is made for mac and easily available here.(=macs on keyboard
some others are not so easily available which have better feel).
and even with 30100 "distorts".
my formula siis this
Code:x=sin(y/512*pi)*31000
and i know in this platform short is -32768 - 32767 which means it can save all numbers what i need... but this kind code produces bigger than this numbers at least when last number is bigger than 30100 i think.
is not exact value i dont yet found exact value.
it seems thisway when i import my sample data in 32bit format loads fine but if i download it 16bit format which it should be based file size and fact how big short is here.
it seems double->signed short conversion is problem int->signed short conversion works.
What's 512?
You're going to have to back that up with actual data, because I don't believe you. (I believe short is that range, but I don't believe that the numbers in the formula are outside that range.)Originally Posted by Vanhapolle
I agree: they can't be if x is short; it's impossible! Even the compiler says it's silly
Code:#include <stdio.h> #include <math.h> #include <limits.h> #include <assert.h> #define PI 3.14159265358979323846 #define PIOVER180 0.01745329251994329577 int main(void) { size_t n; int thingy; // No idea what this is short thing; // No idea what this is printf("SHRT_MAX = %d\n", SHRT_MAX); for (n = 0; n < 1000000; n++) { thing = (PI * n / 512) * 31000; // Mystery thing assert(thing >= SHRT_MIN && thing <= SHRT_MAX); thingy = (short)((PI * n / 512) * 31000); if (thingy > SHRT_MAX) printf("SOMETHING'S WRONG! thing == %d\n", thingy); } return 0; }Code:$ gcc -Wall -Wextra van.c -lm van.c: In function ‘main’: van.c:19:9: warning: comparison is always true due to limited range of data type [-Wtype-limits] assert(thing >= SHRT_MIN && thing <= SHRT_MAX); ^ van.c:19:9: warning: comparison is always true due to limited range of data type [-Wtype-limits]
If y is an integral type, y/512 will be rounded toward zero. That will affect the shape of results (e.g. the visual shape of the curve produced if x is plotted against y). However, sin() returns a value in [-1,1] so x is guaranteed to be in the range [-31000,31000].
Then some code other than what you have shown is causing your problem.
For example, if some other code is molesting a pointer and overwriting x after the expression you've shown is complete, that might explain what is going on.
My guess is that, in converting your code from 32-bit variables/operations to 16-bit you have changed something incorrectly. In other words, a programming error in some code you haven't shown.
Try providing a small but complete (in the sense that other people can compile/link/execute it, supply it with relevant input data, and reproduce your problem) sample of code. In the process of creating such an example, you might have an "aha!" moment and realise what the problem is. If not, then people will have a chance of helping you.
