Is there a one-line function that generates a triangle wave?

Question

In a similar way that modulo generates a sawtooth wave. It doesn\'t have to be continuous.

here is what i mean:

int m = 10;
int x = 0;
int i         


        

Answer 1

Try this:

x = m - abs(m - 2*(i++ % m))

Answer 2

I've tested it with a simple loop and you guys haven't answered the man's question at all. Cut and pasting won't help people. No wonder so many mass media hoaxes have so much success. With a folks that repeats mistakes of others that cannot be any surprise is it. And people even give positive reputation rates for these wrong answers?! Unbelievable! But again, this parallels with my previous remark.

So first off we are going to explain to our folks what a TRIANGLE wave IS. Well it is a wave which has a period consisting of TWO equal sloped ramps. A ramp sloped UP and a ramp equally as the first but sloped DOWN contrary to a SAWTOOTH which has a ramp sloped UP or a ramp sloped DOWN repeated after a reversed talud.

PS: The last one who gave "y(x)=(2a/π)arcsin(sin((2π/p)*x))" is too complicated, we are looking for a fast c++ routine so trigonometry is absolutely out of the question.

Test routine:

(...)

for (byte V=0; V<255; V++)
{
unsigned int x = evenramp(V);
plotRGB(0,0,x,x,x);
delay(100); // make sure you have your own delay function declared of course

/* use your own graphic function !!! plotRGB(row,column,R,G,B) */
/* the light intensity will give you the change of value V in time */
/* all functions suggested as answer give SAWTOOTH and NOT TRIANGLE */
/* it is a TRIANGLE the man wants */
}

float triangleattempt(unsigned int x) // place any answered formula after '255 *' behind return.
{
return 255 * (255 - abs(255 - 2*(x % 255))); // this will show a SAWTOOTH
}

//All given answers up to now excluding "function  xs ( xx : float ): float" (this is not the requested one-liner, sorry) that are not a symmetrical triangle wave

// m - abs(i % (2*m) - m); (this is still a SAWTOOTH wave and not a TRIANGLE wave)
// abs((x++ % 6) - 3); (this is still a SAWTOOTH wave and not a TRIANGLE wave)
// abs(amplitude - x % (2*amplitude)); (this is still a SAWTOOTH wave and not a TRIANGLE wave)

=> I found a source which tells exactly what the answer is in mathematical notation: http://mathworld.wolfram.com/TriangleWave.html

I have tested the formula on a Linux program called KmPlot. Linux users can get kmplot via the root terminal typing apt-get install kmplot and if that doesn't work try using the regular terminal and type sudo apt-get install kmplot and if that doesn't work watch this youtube video for general instructions on installing a Linux program http://www.youtube.com/watch?v=IkhcwxC0oUg

SO A CORRECT ANSWER to the thread question is an example of a symmetrical triangle function declaration in c++ form shown below:

(...)

int symetrictriangle(float x)
{
unsigned int period = 30; // number of increases of x before a new cycle begins
unsigned int amplitude = 100; // top to bottom value while the bottom value is always zero
return amplitude * 2 * abs(round(x/period)-(x/period));
}

(...)

Cheerz!