生成C语言goto代码示例
时间: 2024-05-05 18:18:51 浏览: 13
好的,我可以帮您生成 C 语言的goto 示例代码。以下是示例代码:
```
#include <stdio.h>
int main() {
int x = 1;
int y = 0;
if (x == 1) {
goto skip;
}
y = 2;
skip:
printf("y = %d\n", y);
return 0;
}
```
这是一个简单的示例,其中使用了 goto 语句来跳过某些代码块。请注意,使用 goto 不是一种良好的编程方法,因为它可能导致代码不易维护和理解。
相关问题
C语言代码:生成个会呼吸的红心
要生成一个会呼吸的红心,你需要使用一些图形库或者游戏引擎。以下是一个使用 SDL2 图形库的 C 语言代码示例,来生成一个会呼吸的红心:
```c
#include <SDL2/SDL.h>
#include <math.h>
#define W 640
#define H 480
const int FPS = 60;
const int NUM_FRAMES = 15;
const int HEART_WIDTH = 150;
const int HEART_HEIGHT = 135;
int main(int argc, char** argv) {
SDL_Window* window = NULL;
SDL_Renderer* renderer = NULL;
SDL_Texture* heart_texture = NULL;
SDL_Rect heart_src_rect = {0, 0, HEART_WIDTH, HEART_HEIGHT};
SDL_Rect heart_dest_rect = {(W - HEART_WIDTH) / 2, (H - HEART_HEIGHT) / 2, HEART_WIDTH, HEART_HEIGHT};
Uint32 start_time = 0;
int frame = 0;
int alpha = 255;
double scale = 1.0;
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
return 1;
}
window = SDL_CreateWindow("Breathing Heart", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, W, H, SDL_WINDOW_SHOWN);
if (window == NULL) {
printf("Window could not be created! SDL_Error: %s\n", SDL_GetError());
return 1;
}
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
if (renderer == NULL) {
printf("Renderer could not be created! SDL_Error: %s\n", SDL_GetError());
return 1;
}
SDL_Surface* heart_surface = SDL_LoadBMP("heart.bmp");
if (heart_surface == NULL) {
printf("Could not load heart image! SDL_Error: %s\n", SDL_GetError());
return 1;
}
heart_texture = SDL_CreateTextureFromSurface(renderer, heart_surface);
if (heart_texture == NULL) {
printf("Could not create heart texture! SDL_Error: %s\n", SDL_GetError());
return 1;
}
SDL_FreeSurface(heart_surface);
SDL_SetTextureBlendMode(heart_texture, SDL_BLENDMODE_BLEND);
// Main loop
while (1) {
start_time = SDL_GetTicks();
SDL_Event event;
while (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT) {
goto quit;
}
}
// Update heart alpha and scale
if (frame < NUM_FRAMES / 2) {
alpha -= 2 * 255 / NUM_FRAMES;
scale += 0.05 / (NUM_FRAMES / 2);
} else {
alpha += 2 * 255 / NUM_FRAMES;
scale -= 0.05 / (NUM_FRAMES / 2);
}
if (alpha < 0) {
alpha = 0;
}
if (alpha > 255) {
alpha = 255;
}
if (scale < 0.5) {
scale = 0.5;
}
if (scale > 1.0) {
scale = 1.0;
}
// Render heart
SDL_SetTextureAlphaMod(heart_texture, alpha);
SDL_RenderCopyEx(renderer, heart_texture, &heart_src_rect, &heart_dest_rect, 0, NULL, SDL_FLIP_NONE);
SDL_RenderPresent(renderer);
// Wait for next frame
Uint32 elapsed_time = SDL_GetTicks() - start_time;
if (elapsed_time < 1000 / FPS) {
SDL_Delay(1000 / FPS - elapsed_time);
}
frame = (frame + 1) % NUM_FRAMES;
}
quit:
SDL_DestroyTexture(heart_texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
```
这段代码使用了一个 `heart.bmp` 的图片文件作为红心的形状,每一帧都会改变红心的透明度和缩放比例,从而呈现出呼吸的效果。你可以根据自己的需求来修改代码中的参数。
自底向上语法分析c语言代码实现
自底向上语法分析可以使用LR分析器来实现。以下是一个简单的C语言语法的LR分析器实现:
1. 定义文法规则:首先需要定义C语言的文法规则,例如:
```
program -> declaration_list
declaration_list -> declaration | declaration_list declaration
declaration -> type_specifier identifier ';'
type_specifier -> 'int' | 'float' | 'char'
identifier -> [a-zA-Z]+
```
2. 构建LR分析表:使用文法规则构建LR分析表,包括状态转移和规约动作。例如,对于上述文法规则,构建的LR分析表如下:
```
State 0:
shift: identifier -> s1
goto: declaration_list -> s2
State 1:
shift: ';' -> s3
State 2:
shift: type_specifier -> s4
State 3:
reduce: identifier -> declaration
reduce: declaration_list -> declaration
State 4:
reduce: type_specifier -> declaration
```
3. 实现LR分析器:根据LR分析表实现LR分析器,例如:
```python
def parse(tokens):
stack = [0]
symbols = ['$']
i = 0
while True:
state = stack[-1]
token = tokens[i]
action = lr_table[state][token]
if action.startswith('s'):
stack.append(int(action[1:]))
symbols.append(token)
i += 1
elif action.startswith('r'):
rule = int(action[1:])
lhs, rhs = grammar[rule]
for _ in rhs:
stack.pop()
symbols.pop()
state = stack[-1]
stack.append(lr_table[state][lhs])
symbols.append(lhs)
elif action == 'acc':
return True
else:
return False
```
4. 测试分析器:使用C语言代码的词法分析器生成的标记作为输入测试分析器。例如:
```python
tokens = ['int', 'identifier', ';']
if parse(tokens):
print('Valid C program')
else:
print('Invalid C program')
```
以上只是一个简单的示例,实际上,C语言的语法比较复杂,需要更多的文法规则和更复杂的LR分析表。
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