c语言 sqrt 源码
时间: 2024-09-18 16:19:01 浏览: 19
C语言标准库中的math.h头文件提供了一个名为sqrt()的函数,用于计算给定实数的平方根。这个函数通常是一个数学库实现的一部分,源码细节可能会因为编译器、操作系统以及具体的实现有所不同。
下面是一个简单的`sqrt()`函数的原理示例,它使用了牛顿法(Newton's method)的大致思路,虽然这不是实际的C语言源码,但它展示了基本的概念:
```c
// 这只是一个简化版本的牛顿法求平方根
double my_sqrt(double x) {
if (x < 0) return -1; // 非正数无实数平方根
double guess = x;
while (true) {
double next_guess = (guess + x / guess) / 2.0; // 新猜测值
if (next_guess * next_guess == x) break; // 如果下一个近似值的平方等于输入值,则找到结果
guess = next_guess; // 否则更新猜测值
}
return guess;
}
```
实际上,如果你想要查看C语言的`sqrt()`函数的具体源码,那通常是系统库如glibc的一部分,这些库代码通常是二进制形式且不可直接查看。如果你想了解其工作原理,建议查阅编译器文档或者查看特定平台的公开源码(如开源的Newlib项目)。
相关问题
图像dct变换C语言源码
下面是一个简单的图像DCT变换的C语言源码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define N 8
void dct(double f[N][N], double F[N][N]) {
double c1, c2, sum;
int i, j, k, l;
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
if (i == 0) {
c1 = sqrt(1.0 / N);
} else {
c1 = sqrt(2.0 / N);
}
if (j == 0) {
c2 = sqrt(1.0 / N);
} else {
c2 = sqrt(2.0 / N);
}
sum = 0.0;
for (k = 0; k < N; k++) {
for (l = 0; l < N; l++) {
sum += f[k][l] * cos((2 * k + 1) * i * M_PI / (2 * N)) * cos((2 * l + 1) * j * M_PI / (2 * N));
}
}
F[i][j] = c1 * c2 * sum;
}
}
}
int main() {
double f[N][N] = {
{140, 144, 147, 140, 140, 155, 179, 175},
{144, 152, 140, 147, 140, 148, 167, 179},
{152, 155, 136, 167, 163, 162, 152, 172},
{168, 145, 156, 160, 152, 155, 136, 160},
{162, 148, 156, 148, 140, 136, 147, 162},
{147, 167, 140, 155, 155, 140, 136, 162},
{136, 156, 123, 167, 162, 144, 140, 147},
{148, 155, 136, 155, 152, 147, 147, 136},
};
double F[N][N];
dct(f, F);
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
printf("%lf ", F[i][j]);
}
printf("\n");
}
return 0;
}
```
这里给出的是一个基于公式计算的DCT变换实现,输入为一个8x8的二维数组,输出为另一个8x8的二维数组。在实际应用中,可能需要对变换结果进行量化和编码等处理,以实现图像压缩的目的。
动态爱心代码c语言源码
```
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<style>
* {
padding: 0;
margin: 0;
}
html,
body {
height: 100%;
padding: 0;
margin: 0;
background: #000;
}
canvas {
position: absolute;
width: 100%;
height: 100%;
}
.aa {
position: fixed;
left: 50%;
bottom: 10px;
color: #ccc;
}
</style>
<body>
<canvas id="pinkboard"></canvas>
<script>
/*
* Settings
*/
var settings = {
particles: {
length: 500, // maximum amount of particles
duration: 2, // particle duration in sec
velocity: 100, // particle velocity in pixels/sec
effect: -0.75, // play with this for a nice effect
size: 30 // particle size in pixels
}
};
/*
* RequestAnimationFrame polyfill by Erik M?ller
*/
(function () {
var b = 0;
var c = ["ms", "moz", "webkit", "o"];
for (var a = 0; a < c.length && !window.requestAnimationFrame; ++a) {
window.requestAnimationFrame = window[c[a] + "RequestAnimationFrame"];
window.cancelAnimationFrame =
window[c[a] + "CancelAnimationFrame"] ||
window[c[a] + "CancelRequestAnimationFrame"];
}
if (!window.requestAnimationFrame) {
window.requestAnimationFrame = function (h, e) {
var d = new Date().getTime();
var f = Math.max(0, 16 - (d - b));
var g = window.setTimeout(function () {
h(d + f);
}, f);
b = d + f;
return g;
};
}
if (!window.cancelAnimationFrame) {
window.cancelAnimationFrame = function (d) {
clearTimeout(d);
};
}
})();
/*
* Point class
*/
var Point = (function () {
function Point(x, y) {
this.x = typeof x !== "undefined" ? x : 0;
this.y = typeof y !== "undefined" ? y : 0;
}
Point.prototype.clone = function () {
return new Point(this.x, this.y);
};
Point.prototype.length = function (length) {
if (typeof length == "undefined")
return Math.sqrt(this.x * this.x + this.y * this.y);
this.normalize();
this.x *= length;
this.y *= length;
return this;
};
Point.prototype.normalize = function () {
var length = this.length();
this.x /= length;
this.y /= length;
return this;
};
return Point;
})();
/*
* Particle class
*/
var Particle = (function () {
function Particle() {
this.position = new Point();
this.velocity = new Point();
this.acceleration = new Point();
this.age = 0;
}
Particle.prototype.initialize = function (x, y, dx, dy) {
this.position.x = x;
this.position.y = y;
this.velocity.x = dx;
this.velocity.y = dy;
this.acceleration.x = dx * settings.particles.effect;
this.acceleration.y = dy * settings.particles.effect;
this.age = 0;
};
Particle.prototype.update = function (deltaTime) {
this.position.x += this.velocity.x * deltaTime;
this.position.y += this.velocity.y * deltaTime;
this.velocity.x += this.acceleration.x * deltaTime;
this.velocity.y += this.acceleration.y * deltaTime;
this.age += deltaTime;
};
Particle.prototype.draw = function (context, image) {
function ease(t) {
return --t * t * t + 1;
}
var size = image.width * ease(this.age / settings.particles.duration);
context.globalAlpha = 1 - this.age / settings.particles.duration;
context.drawImage(
image,
this.position.x - size / 2,
this.position.y - size / 2,
size,
size
);
};
return Particle;
})();
/*
* ParticlePool class
*/
var ParticlePool = (function () {
var particles,
firstActive = 0,
firstFree = 0,
duration = settings.particles.duration;
function ParticlePool(length) {
// create and populate particle pool
particles = new Array(length);
for (var i = 0; i < particles.length; i++)
particles[i] = new Particle();
}
ParticlePool.prototype.add = function (x, y, dx, dy) {
particles[firstFree].initialize(x, y, dx, dy);
// handle circular queue
firstFree++;
if (firstFree == particles.length) firstFree = 0;
if (firstActive == firstFree) firstActive++;
if (firstActive == particles.length) firstActive = 0;
};
ParticlePool.prototype.update = function (deltaTime) {
var i;
// update active particles
if (firstActive < firstFree) {
for (i = firstActive; i < firstFree; i++)
particles[i].update(deltaTime);
}
if (firstFree < firstActive) {
for (i = firstActive; i < particles.length; i++)
particles[i].update(deltaTime);
for (i = 0; i < firstFree; i++) particles[i].update(deltaTime);
}
// remove inactive particles
while (
particles[firstActive].age >= duration &&
firstActive != firstFree
) {
firstActive++;
if (firstActive == particles.length) firstActive = 0;
}
};
ParticlePool.prototype.draw = function (context, image) {
// draw active particles
if (firstActive < firstFree) {
for (i = firstActive; i < firstFree; i++)
particles[i].draw(context, image);
}
if (firstFree < firstActive) {
for (i = firstActive; i < particles.length; i++)
particles[i].draw(context, image);
for (i = 0; i < firstFree; i++) particles[i].draw(context, image);
}
};
return ParticlePool;
})();
/*
* Putting it all together
*/
(function (canvas) {
var context = canvas.getContext("2d"),
particles = new ParticlePool(settings.particles.length),
particleRate =
settings.particles.length / settings.particles.duration, // particles/sec
time;
// get point on heart with -PI <= t <= PI
function pointOnHeart(t) {
return new Point(
160 * Math.pow(Math.sin(t), 3),
130 * Math.cos(t) -
50 * Math.cos(2 * t) -
20 * Math.cos(3 * t) -
10 * Math.cos(4 * t) +
25
);
}
// creating the particle image using a dummy canvas
var image = (function () {
var canvas = document.createElement("canvas"),
context = canvas.getContext("2d");
canvas.width = settings.particles.size;
canvas.height = settings.particles.size;
// helper function to create the path
function to(t) {
var point = pointOnHeart(t);
point.x =
settings.particles.size / 2 +
(point.x * settings.particles.size) / 350;
point.y =
settings.particles.size / 2 -
(point.y * settings.particles.size) / 350;
return point;
}
// create the path
context.beginPath();
var t = -Math.PI;
var point = to(t);
context.moveTo(point.x, point.y);
while (t < Math.PI) {
t += 0.01; // baby steps!
point = to(t);
context.lineTo(point.x, point.y);
}
context.closePath();
// create the fill
context.fillStyle = "#ea80b0";
context.fill();
// create the image
var image = new Image();
image.src = canvas.toDataURL();
return image;
})();
// render that thing!
function render() {
// next animation frame
requestAnimationFrame(render);
// update time
var newTime = new Date().getTime() / 1000,
deltaTime = newTime - (time || newTime);
time = newTime;
// clear canvas
context.clearRect(0, 0, canvas.width, canvas.height);
// create new particles
var amount = particleRate * deltaTime;
for (var i = 0; i < amount; i++) {
var pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random());
var dir = pos.clone().length(settings.particles.velocity);
particles.add(
canvas.width / 2 + pos.x,
canvas.height / 2 - pos.y,
dir.x,
-dir.y
);
}
// update and draw particles
particles.update(deltaTime);
particles.draw(context, image);
}
// handle (re-)sizing of the canvas
function onResize() {
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
}
window.onresize = onResize;
// delay rendering bootstrap
setTimeout(function () {
onResize();
render();
}, 10);
})(document.getElementById("pinkboard"));
</script>
</body>
</html>
```
![示例图片](https://devbit-static.oss-cn-beijing.aliyuncs.com/devbit-static/img/heart.png)