user-0 提问: 怎么搞才能让计算的精度提高了

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user: user-1
content: 希望对你有帮助：https://blog.csdn.net/it_xiangqiang/category_10581430.html 希望对你有帮助：https://blog.csdn.net/it_xiangqiang/category_10768339.html

user: user-2
content: #pragma warning(disable:4996) /*--------------------------------------- 函数型计算器(VC++6.0,Win32 Console) 功能： 目前提供了10多个常用数学函数: ⑴正弦sin ⑵余弦cos ⑶正切tan ⑷开平方sqrt ⑸反正弦arcsin ⑹反余弦arccos ⑺反正切arctan ⑻常用对数lg ⑼自然对数ln ⑽ｅ指数exp ⑾乘幂函数^ ⑿向上取整ceil ⒀向下取整floor ⒁四舍五入取整round ⒂取符号sign ⒃取绝对值abs 用法： 如果要求2的32次幂，可以打入2^32<回车> 如果要求30度角的正切可键入tan(Pi/6)<回车> 注意不能打入：tan(30)<Enter> 如果要求1.23弧度的正弦，有几种方法都有效： sin(1.23)<Enter> sin 1.23 <Enter> sin1.23  <Enter> 如果验证正余弦的平方和公式,可打入sin(1.23)^2+cos(1.23)^2 <Enter>或sin1.23^2+cos1.23^2 <Enter> 此外两函数表达式连在一起,自动理解为相乘如：sin1.23cos0.77+cos1.23sin0.77就等价于sin(1.23)*cos(0.77)+cos(1.23)*sin(0.77) 当然你还可以依据三角变换，再用sin(1.23+0.77)也即sin2验证一下。 本计算器充分考虑了运算符的优先级因此诸如：2+3*4^2 实际上相当于：2+(3*(4*4)) 另外函数名前面如果是数字,那么自动认为二者相乘. 同理，如果某数的右侧是左括号，则自动认为该数与括弧项之间隐含一乘号。 如：3sin1.2^2+5cos2.1^2 相当于3*sin2(1.2)+5*cos2(2.1) 又如：4(3-2(sqrt5-1)+ln2)+lg5 相当于4*(3-2*(√5 -1)+loge(2))+log10(5) 此外，本计算器提供了圆周率Pi键入字母时不区分大小写,以方便使用。 16进制整数以0x或0X开头。 ----------------------------------------*/ #include <iostream> #include <iomanip> #include <cstdlib> #include <cstring> #include <cctype> #include <cmath> #include <stdio.h> #include <string.h> #include <windows.h> using namespace std; const char Tab = 0x9; const int  DIGIT = 1; const int MAXLEN = 16384; char s[MAXLEN], *endss; int pcs = 15; double sign(double dVal) {          if (dVal>0.0) return  1.0;     else if (dVal<0.0) return -1.0;     else               return  0.0; } double round(double dVal, short iPlaces) {//iPlaces>=0     char s[30];     double dRetval;      sprintf(s, "%.*lf", iPlaces, dVal);     sscanf(s, "%lf", &dRetval);     return (dRetval); } double fun(double x, char op[], int *iop) {     while (op[*iop - 1]<32) //本行使得函数嵌套调用时不必加括号,如 arc sin(sin(1.234)) 只需键入arc sin sin 1.234<Enter>         switch (op[*iop - 1]) {         case  7: x = sin(x);    (*iop)--; break;         case  8: x = cos(x);    (*iop)--; break;         case  9: x = tan(x);    (*iop)--; break;         case 10: x = sqrt(x);   (*iop)--; break;         case 11: x = asin(x);   (*iop)--; break;         case 12: x = acos(x);   (*iop)--; break;         case 13: x = atan(x);   (*iop)--; break;         case 14: x = log10(x);  (*iop)--; break;         case 15: x = log(x);    (*iop)--; break;         case 16: x = exp(x);    (*iop)--; break;         case 17: x = ceil(x);   (*iop)--; break;         case 18: x = floor(x);  (*iop)--; break;         case 19: x = round(x,0);(*iop)--; break;         case 20: x = sign(x);   (*iop)--; break;         case 21: x = fabs(x);   (*iop)--; break;         }     return x; } double calc(char *expr, char **addr) {     static int deep; //递归深度     static char *fname[] = { "sin","cos","tan","sqrt","arcsin","arccos","arctan","lg","ln","exp","ceil","floor","round","sign","abs",NULL };     double ST[10] = { 0.0 }; //数字栈     char op[10] = { '+' }; //运算符栈     char c, *rexp, *pp, *pf;     int ist = 1, iop = 1, last, i, n;     __int64 i64;      if (!deep) {         pp = pf = expr;         do {             c = *pp++;             if (c != ' '&& c != Tab)                 *pf++ = c;         } while (c != '\0');     }     pp = expr;     if ((c = *pp) == '-' || c == '+') {         op[0] = c;         pp++;     }     last = !DIGIT;     while ((c = *pp) != '\0') {         if (c == '(') {//左圆括弧             deep++;             ST[ist++] = calc(++pp, addr);             deep--;             ST[ist - 1] = fun(ST[ist - 1], op, &iop);             pp = *addr;             last = DIGIT;             if (*pp == '(' || isalpha(*pp) && strnicmp(pp, "Pi", 2)) {//目的是：当右圆括弧的右恻为左圆括弧或函数名字时，默认其为乘法                 op[iop++] = '*';                 last = !DIGIT;                 c = op[--iop];                 goto operate;             }         }         else if (c == ')') {//右圆括弧             pp++;             break;         }         else if (isalpha(c)) {             if (!strnicmp(pp, "Pi", 2)) {                 if (last == DIGIT) {                     wcout <<    L"π左侧遇）" << endl; exit(1);                 }                 ST[ist++] = 3.14159265358979323846264338328;                 ST[ist - 1] = fun(ST[ist - 1], op, &iop);                 pp += 2;                 last = DIGIT;                 if (!strnicmp(pp, "Pi", 2)) {                     wcout <<    L"两个π相连" << endl; exit(2);                 }                 if (*pp == '(') {                     wcout <<    L"π右侧遇（" << endl; exit(3);                 }             }             else {                 for (i = 0; (pf = fname[i]) != NULL; i++)                     if (!strnicmp(pp, pf, strlen(pf))) break;                 if (pf != NULL) {                     op[iop++] = 07 + i;                     pp += strlen(pf);                 }                 else {                     wcout <<    L"陌生函数名" << endl; exit(4);                 }             }         }         else if (c == '+' || c == '-' || c == '*' || c == '/' || c == '%' || c == '^') {             char cc;             if (last != DIGIT) {                 wcout <<    L"运算符粘连" << endl; exit(5);             }             pp++;             if (c == '+' || c == '-') {                 do {                     cc = op[--iop];                     --ist;                     switch (cc) {                     case '+':  ST[ist - 1] += ST[ist]; break;                     case '-':  ST[ist - 1] -= ST[ist]; break;                     case '*':  ST[ist - 1] *= ST[ist]; break;                     case '/':  ST[ist - 1] /= ST[ist]; break;                     case '%':  ST[ist - 1] = fmod(ST[ist - 1], ST[ist]); break;                     case '^':  ST[ist - 1] = pow(ST[ist - 1], ST[ist]); break;                     }                 } while (iop);                 op[iop++] = c;             }             else if (c == '*' || c == '/' || c == '%') {             operate:        cc = op[iop - 1];                 if (cc == '+' || cc == '-') {                     op[iop++] = c;                 }                 else {                     --ist;                     op[iop - 1] = c;                     switch (cc) {                     case '*':  ST[ist - 1] *= ST[ist]; break;                     case '/':  ST[ist - 1] /= ST[ist]; break;                     case '%':  ST[ist - 1] = fmod(ST[ist - 1], ST[ist]); break;                     case '^':  ST[ist - 1] = pow(ST[ist - 1], ST[ist]); break;                     }                 }             }             else {                 cc = op[iop - 1];                 if (cc == '^') {                     wcout <<    L"乘幂符连用" << endl; exit(6);                 }                 op[iop++] = c;             }             last = !DIGIT;         }         else {             if (last == DIGIT) {                 wcout <<    L"两数字粘连" << endl; exit(7);             }             if (pp[0] == '0' && (pp[1] == 'x' || pp[1] == 'X')) {                 sscanf(pp + 2, "%I64x%n", &i64, &n);                 rexp = pp + 2 + n;                 ST[ist++] = (double)i64;             }             else ST[ist++] = strtod(pp, &rexp);             ST[ist - 1] = fun(ST[ist - 1], op, &iop);             if (pp == rexp) {                 wcout <<    L"非法字符" << endl; exit(8);             }             pp = rexp;             last = DIGIT;             if (*pp == '(' || isalpha(*pp)) {                 op[iop++] = '*';                 last = !DIGIT;                 c = op[--iop];                 goto operate;             }         }     }     *addr = pp;     if (iop >= ist) {         wcout <<    L"表达式有误" << endl; exit(9);     }     while (iop) {         --ist;         switch (op[--iop]) {         case '+':  ST[ist - 1] += ST[ist]; break;         case '-':  ST[ist - 1] -= ST[ist]; break;         case '*':  ST[ist - 1] *= ST[ist]; break;         case '/':  ST[ist - 1] /= ST[ist]; break;         case '%':  ST[ist - 1] = fmod(ST[ist - 1], ST[ist]); break;         case '^':  ST[ist - 1] = pow(ST[ist - 1], ST[ist]); break;         }     }     return ST[0]; } int main(int argc, char **argv) {     int a;      wcout.imbue(locale("chs"));     if (argc<2) {         //if (GetConsoleOutputCP() != 936) system("chcp 936>NUL");//中文代码页         wcout <<    L"计算函数表达式的值。" << endl << L"支持(),+,-,*,/,%,^,Pi,sin,cos,tan,sqrt,arcsin,arccos,arctan,lg,ln,exp,ceil,floor,round,sign,abs" << endl;         while (1) {             wcout <<    L"请输入表达式：";             fgets(s,16384,stdin);             if ('\n' == s[strlen(s)-1]) s[strlen(s) - 1] = 0;             if (s[0] == 0) break;//             cout << s << "=";             cout << setprecision(15) << calc(s, &endss) << endl;         }     }     else if (argc == 2 && 0 == strcmp(argv[1], "/?")) {         //if (GetConsoleOutputCP() != 936) system("chcp 936>NUL");//中文代码页         wcout <<    L"计算由≥1个命令行参数给出的函数表达式的值。\n"             "最后一个参数是.0～.15表示将计算结果保留小数0～15位\n"             "最后一个参数是x表示将计算结果以16进制正整数格式输出\n"             "支持(),+,-,*,/,%,^^,Pi,sin,cos,tan,sqrt,arcsin,arccos,arctan,lg,ln,exp,ceil,floor,round,sign,abs\n"             "16进制整数以0x或0X开头\n";     }     else {         strncpy(s, argv[1], MAXLEN - 1); s[MAXLEN - 1] = 0;         if (argc>2) {             for (a = 2; a<argc - 1; a++) strncat(s, argv[a], MAXLEN - 1);//将空格间隔的各参数连接到s             if (1 == sscanf(argv[a], ".%d", &pcs) && 0 <= pcs && pcs <= 15) {//最后一个参数是.0～.15表示将计算结果保留小数0～15位                 printf("%.*lf\n", pcs, calc(s, &endss));             }             else if (argv[a][0] == 'x' || argv[a][0] == 'X') {//最后一个参数是x表示将计算结果以16进制正整数格式输出                 printf("0x%016I64x\n", (__int64)calc(s, &endss));             }             else {                 strncat(s, argv[a], MAXLEN - 1);                 printf("%.15lg\n", calc(s, &endss));             }         }         else {             printf("%.15lg\n", calc(s, &endss));         }     }     return 0; }