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#16
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Re: remainder function
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#17
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Re: remainder function
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Code:
double myRemainder(double x, double y){
return x-y*floor(0.5+x/y);
}
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#18
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Re: remainder function
What about:
Code:
double EthersRemainder( double x, double y ){
int wholenumber;
wholenumber = (int)(x/y);
double result;
result = (x - (wholenumber * y));
if(result > 0.5*y) {
result -= y;
}
return result;
}
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#19
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Re: remainder function
That's not my remainder.
Did you compile and run it ? It doesn't work correctly. I'm sure that there's a way, with enough conditional logic, to torture fmod() or % into into a remainder* function, but what I am really asking in this thread is a) does the C++ compiler provided with FRC have the remainder* function, and b) does it behave like this: *This* is my remainder: Code:
double myRemainder(double x, double y){
return x-y*floor(0.5+x/y);
}
*per IEC 60559 as specified on Page 235 Section 7.12.10.2 of ISO/IEC 9899:TC3 Last edited by Ether : 01-02-2013 at 16:11. |
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#20
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Re: remainder function
If you have a function that works, then use it?
I don't understand your qualm? I have not ever encountered a programming scenario where modulus division didn't solve my desire for a remainder, so I'm a bit lost. If there doesn't exist an operator that does what you want, then you need to either a) fabricate a solution from the operators you have access to, or b) find a library that does that for you. |
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#21
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Re: remainder function
I do use it. But I don't want to be telling other people to use my custom function if there's already a perfectly good remainder function provided with FRC C++. I don't have access to a working C++ installation, otherwise I would test it myself. I am seeking help from knowledgeable C++ users on this forum.
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For example, the IEC60559 remainder function can take any angle and normalize it to the range -180..+180 with a single C instruction: normalizedAngle = remainder(angle,360); I'd like to know if the remainder function is supported in FRC C++ so I can recommend it to students who are trying to do this type of conversion. Neither the fmod() function nor the % operator can replicate the functionality of the remainder() function without using a bunch of conditional logic If there are any Java programmers following this thread, Java appears to have the IEC 60559 remainder function; in Java it is called IEEERemainder. See attachments. If someone would be willing to test that (compare it to the implementation I posted ealier in this thread) I'd be grateful. qualm /kwä(l)m/ Noun 1) An uneasy feeling of doubt, worry, or fear; a misgiving. 2) A momentary faint or sick feeling. Synonyms nausea - queasiness |
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#22
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Re: remainder function
In a Java SE project this
Code:
double result;
double x[] = {179, 180, 181, 359, 721, -1, -179, -180, -359, -361, -721};
for (int i = 0; i < x.length; i++){
result = Math.IEEEremainder(x[i],360.0);
System.out.println("x: " + x[i] + " rem y: 360 result: " + result);
}
Code:
x: 179.0 rem y: 360 result: 179.0 x: 180.0 rem y: 360 result: 180.0 x: 181.0 rem y: 360 result: -179.0 x: 359.0 rem y: 360 result: -1.0 x: 721.0 rem y: 360 result: 1.0 x: -1.0 rem y: 360 result: -1.0 x: -179.0 rem y: 360 result: -179.0 x: -180.0 rem y: 360 result: -180.0 x: -359.0 rem y: 360 result: 1.0 x: -361.0 rem y: 360 result: -1.0 x: -721.0 rem y: 360 result: -1.0 However I cannot use IEEERemainder() in an FRC project they have compiled the jar without it apparently. Last edited by omalleyj : 01-02-2013 at 19:16. Reason: still can't spell after all these years |
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#23
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Re: remainder function
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Are there any C++ gurus out there who can look into the same question for C++ ? |
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#24
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Re: remainder function
That's not entirely true. FRC uses the Squawk JVM, which is based on Java ME. Java ME does not require IEEERemainder(), which is why it isn't in java.lang.Math. However, Squawk does implement some features from Java SE, and puts them in other packages. In this case, IEEERemainder is in the com.sun.squawk.util.MathUtils package.
Last edited by Joe Ross : 01-02-2013 at 20:42. |
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#25
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Re: remainder function
Thanks!
Is there a cross reference of where SE stuff that's been moved can be found? Last edited by omalleyj : 01-02-2013 at 20:46. Reason: added a question |
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#26
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Re: remainder function
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#27
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Re: remainder function
Here's the result from the robot
Code:
double result;
double x[] = {179, 180, 181, 359, 721, -1, -179, -180, -359, -361, -721};
for (int i = 0; i < x.length; i++){
result = MathUtils.IEEEremainder(x[i],360.0);
System.out.println("x: " + x[i] + " rem y: 360 result: " + result);
}
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#28
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Re: remainder function
It's all in the javadocs, but I'm not aware of an easy cross reference.
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#29
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Re: remainder function
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#30
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Re: remainder function
From my installation, a grep through the headers folder shows no remainder functions. It's possible I'm missing something, but it looks like it doesn't exist at all in the vxWorks API.
As for the extern "C" option, yes that will make it compile, however the function will most likely not be resolved by the linker, which will cause problems when you try to run it. Wind River's system is designed to not complain about missing symbols until the cRIO's kernel tries to load the program. I'll check if this is the case tomorrow. EDIT: actually, drem() does exist, and is defined to be the same as remainder() (see the glibc manual). However, the definition for it is in <private/trigP.h>, which isn't meant for inclusion by user programs. There don't seem to be any public headers which include it either. Last edited by Radical Pi : 02-02-2013 at 02:37. |
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