C Const

Posted 2020-11-12

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绫诲瀷闄愬畾璇?const 

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const int nochange; /* constant */
nochange = 12 /* false */

鍙互鍒濆鍖栦竴涓猚onst 鍙橀噺锛?鍒濆鍖栦箣鍚庯紝涓嶅彲浠ュ啀鏀瑰彉瀹冦€?/p>

const int nochange = 12  // true
const int days1[3] = {31,30,31}; // true

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鐗瑰埆娉ㄦ剰鍖哄垎锛?鎸囬拡鏈韩鏄痗onst     涓?nbsp;       鎸囬拡鎸囧悜鐨勫€兼槸const

const 绱ф尐鐫€鐨勬槸浠€涔堬紝浠€涔堝氨鏄笉鍙樼殑

const int days1[3] = {31,30,31}; // true  鐩稿綋浜?const int *days1 ;  const鍦?* 宸﹁竟锛?浣垮緱鏁版嵁鎴愪负甯搁噺

const float *pf  锛?// const 绱ф尐鐫€ float ,璇存槑 float甯搁噺鏄笉鍙樼殑

float *const pt ;  // const绱ф尐鐫€ 鎸囬拡pt锛岃鏄庢槸涓€涓父閲忔寚閽?/span>

float const *pt; // const绱ф尐鐫€ *pt, 鐩稿綋浜庤В寮曠敤锛屾槸float 甯搁噺锛屼笉鏄寚閽堬紝娉ㄦ剰鍖哄垎

鍚庨潰鏈夋洿濂界殑鐞嗚В鏂规硶锛侊紒锛?/span>

1. 鎸囬拡鎸囧悜鐨勫€兼槸const

const float *pf ;  // pf 鎸囧悜涓€涓父閲?/p>

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float const *pfc; // 绛夊悓浜?const float *pfc

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鎬讳箣锛氫笅闈㈢悊瑙ｈ捣鏉ユ瘮杈冨鏄?/span>

涓€涓綅浜?span style="background-color: #ffff00;"> *宸﹁竟 浠绘剰浣嶇疆鐨?const 浣垮緱 鏁版嵁鎴愪负甯搁噺 

鑰?涓€涓綅浜?* 鍙宠竟 鐨刢onst浣垮緱  鎸囬拡鑷韩鎴愪负甯搁噺 銆?/p>

 

浣嗘槸pf鏈韩鐨勫€兼槸鍙互鏀瑰彉鐨勶紙鏈韩鏄釜鍦板潃锛夛紝瀹冨彲浠ユ寚鍚戝彟涓€涓猚onst鍊?/span>銆?/p>

eg:

const float *pf_new;

pf  = pf_new;

2. 鎸囬拡鏈韩鏄痗onst (鎸囬拡鏈韩鐨勫€间笉鍙彉)

eg:

float * const pt;  // pt 鏄竴涓父閲忔寚閽?/p>

绛夊悓浜庝笅闈㈢殑鍐欐硶

float const *pt // pt 鏄竴涓父閲忔寚閽?/p>

蹇呴』鎬绘槸鎸囧悜鍚屼竴涓湴鍧€锛屼絾鎵€鎸囧悜鐨勫€煎彲浠ユ敼鍙樸€?/span>

3.  鍦板潃鏄父閲忥紝鍦板潃鎸囧悜鐨勫唴瀹逛篃鏄父閲?/span>

const float * const ptr;

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4.  甯歌鐢ㄦ硶

甯歌鐢ㄦ硶鏄０鏄庝綔涓哄嚱鏁板舰寮忓弬閲忕殑鎸囬拡銆?/span>

eg:

涓€涓悕涓篸isplay()鐨勫嚱鏁版樉绀轰竴涓暟缁勭殑鍐呭銆?涓轰簡浣跨敤瀹冿紝鍙互鎶婃暟缁勫悕浣滀负鍙傛暟浼犻€侊紝浣嗘暟缁勫悕鏄竴涓湴鍧€锛?/span>

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void display(const int array[], int limit);

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5. 瀵瑰叏灞€鏁版嵁浣跨敤const

6. const 鎸囬拡鍙橀噺闂寸殑璧嬪€煎叧绯?/span>

const鎸囬拡 蹇呴』 璧嬪€肩粰 const 鎸囬拡

浣嗘槸锛岄潪const鍨嬫寚閽?鍙互 璧嬪€肩粰cons鎸囬拡

7 QAC 0431

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