CORDIC: Difference between revisions

</pre>

=={{header|Rust}}==

{{trans|C}}

<syntaxhighlight lang="Rust">

use std::f64::consts::PI;

// Constants for angles and kvalues

const ANGLES: [f64; 28] = [

0.78539816339745, 0.46364760900081, 0.24497866312686, 0.12435499454676,

0.06241880999596, 0.03123983343027, 0.01562372862048, 0.00781234106010,

0.00390623013197, 0.00195312251648, 0.00097656218956, 0.00048828121119,

0.00024414062015, 0.00012207031189, 0.00006103515617, 0.00003051757812,

0.00001525878906, 0.00000762939453, 0.00000381469727, 0.00000190734863,

0.00000095367432, 0.00000047683716, 0.00000023841858, 0.00000011920929,

0.00000005960464, 0.00000002980232, 0.00000001490116, 0.00000000745058,

];

const KVALUES: [f64; 24] = [

0.70710678118655, 0.63245553203368, 0.61357199107790, 0.60883391251775,

0.60764825625617, 0.60735177014130, 0.60727764409353, 0.60725911229889,

0.60725447933256, 0.60725332108988, 0.60725303152913, 0.60725295913894,

0.60725294104140, 0.60725293651701, 0.60725293538591, 0.60725293510314,

0.60725293503245, 0.60725293501477, 0.60725293501035, 0.60725293500925,

0.60725293500897, 0.60725293500890, 0.60725293500889, 0.60725293500888,

];

// Function to convert degrees to radians

fn radians(degrees: f64) -> f64 {

degrees * PI / 180.0

}

// Cordic algorithm implementation

fn cordic(alpha: f64, n: usize, c_cos: &mut f64, c_sin: &mut f64) {

let mut theta = 0.0;

let mut pow2 = 1.0;

let mut x = 1.0;

let mut y = 0.0;

let newsgn = if (alpha / (2.0 * PI)).floor() as i32 % 2 == 1 { 1.0 } else { -1.0 };

if alpha < -PI / 2.0 || alpha > PI / 2.0 {

if alpha < 0.0 {

cordic(alpha + PI, n, &mut x, &mut y);

} else {

cordic(alpha - PI, n, &mut x, &mut y);

}

*c_cos = x * newsgn;

*c_sin = y * newsgn;

return;

}

let ix = if n - 1 > 23 { 23 } else { n - 1 };

let kn = KVALUES[ix];

for i in 0..n {

let atn = ANGLES[i];

let sigma = if theta < alpha { 1.0 } else { -1.0 };

theta += sigma * atn;

let t = x;

x -= sigma * y * pow2;

y += sigma * t * pow2;

pow2 /= 2.0;

}

*c_cos = x * kn;

*c_sin = y * kn;

}

fn main() {

let mut c_cos: f64;

let mut c_sin: f64;

let test_angles = [-9.0, 0.0, 1.5, 6.0];

println!(" x sin(x) diff. sine cos(x) diff. cosine");

for th in (-90..=90).step_by(15) {

let thr = radians(th as f64);

c_cos = 0.0;

c_sin = 0.0;

cordic(thr, 24, &mut c_cos, &mut c_sin);

println!("{:+03}.0° {:+.8} ({:+.8}) {:+.8} ({:+.8})", th, c_sin, c_sin - thr.sin(), c_cos, c_cos - thr.cos());

}

println!("\nx(rads) sin(x) diff. sine cos(x) diff. cosine");

for &angle in &test_angles {

let thr = angle;

c_cos = 0.0;

c_sin = 0.0;

cordic(thr, 24, &mut c_cos, &mut c_sin);

println!("{:+4.1} {:+.8} ({:+.8}) {:+.8} ({:+.8})", thr, c_sin, c_sin - thr.sin(), c_cos, c_cos - thr.cos());

}

}

</syntaxhighlight>

{{out}}

<pre>

x sin(x) diff. sine cos(x) diff. cosine

-90.0° -1.00000000 (+0.00000000) -0.00000007 (-0.00000007)

-75.0° -0.96592585 (-0.00000003) +0.25881895 (-0.00000009)

-60.0° -0.86602545 (-0.00000005) +0.49999992 (-0.00000008)

-45.0° -0.70710684 (-0.00000006) +0.70710672 (-0.00000006)

-30.0° -0.49999992 (+0.00000008) +0.86602545 (+0.00000005)

-15.0° -0.25881895 (+0.00000009) +0.96592585 (+0.00000003)

+00.0° +0.00000007 (+0.00000007) +1.00000000 (-0.00000000)

+15.0° +0.25881895 (-0.00000009) +0.96592585 (+0.00000003)

+30.0° +0.49999992 (-0.00000008) +0.86602545 (+0.00000005)

+45.0° +0.70710684 (+0.00000006) +0.70710672 (-0.00000006)

+60.0° +0.86602545 (+0.00000005) +0.49999992 (-0.00000008)

+75.0° +0.96592585 (+0.00000003) +0.25881895 (-0.00000009)

+90.0° +1.00000000 (-0.00000000) -0.00000007 (-0.00000007)

x(rads) sin(x) diff. sine cos(x) diff. cosine

-9.0 -0.41211842 (+0.00000006) -0.91113029 (-0.00000003)

+0.0 +0.00000007 (+0.00000007) +1.00000000 (-0.00000000)

+1.5 +0.99749499 (+0.00000000) +0.07073719 (-0.00000002)

+6.0 -0.27941552 (-0.00000002) +0.96017028 (-0.00000001)