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C语言写的代码能计算加减乘除表达式，但是不能计算平方和三角函数
// EX6_08.CPP
// A program to implement a calculator
#include <stdio.h> // For input/output
#include <stdlib.h> // For the exit() function
#include <ctype.h> // For the isdigit() function
#include <string.h> // For the strcpy() function
void eatspaces(char * str); // Function to eliminate blanks
double expr(char * str); // Function evaluating an expression
double term(char * str, int * pindex); // Function analyzing a term
double number(char * str, int * pindex); // Function to recognize a number
char * extract(char * str, int * index); // Function to extract a substring
const int MAX = 80; // Maximum expression length including ""\0""
int main(void)
{
char buffer[MAX]; // Input area for expression to be evaluated
char c;
int i;
printf("Welcome to your friendly calculator.\n");
printf("Enter an expression, or an empty line to quit.\n");
for(;;)
{
i=0;
scanf("%c",&c); // Read an input line
while(c!=""\n"")
{
buffer[i++]=c;
scanf("%c",&c);
}
buffer[i]=""\0"";
eatspaces(buffer); // Remove blanks from input
if(!buffer[0]) // Empty line ends calculator
return 0;
printf( "\t= %f\n\n",expr(buffer)); // Output value of expression
}
}
// Function to eliminate blanks from a string
void eatspaces(char * str)
{
int i=0; // ""Copy to"" index to string
int j=0; // ""Copy from"" index to string
while((*(str+i) = *(str+j++)) != ""\0"") // Loop while character copied is not \0
if(*(str+i) != "" "") // Increment i as long as
i++; // character is not a blank
return;
}
// Function to evaluate an arithmetic expression
double expr(char * str)
{
double value = 0; // Store result here
int index = 0; // Keeps track of current character position
value = term(str, &index); // Get first term
for(;;) // Infinite loop, all exits inside
{
switch(*(str+index++)) // Choose action based on current character
{
case ""\0"": // We""re at the end of the string
return value; // so return what we have got
case ""+"": // + found so add in the
value += term(str, &index); // next term
break;
case ""-"": // - found so subtract
value -= term(str, &index); // the next term
break;
default: // If we reach here the string
printf("Arrrgh!*#!! There""s an error.\n");
exit(1);
}
}
}
// Function to get the value of a term
double term(char * str, int * pindex)
{
double value = 0; // Somewhere to accumulate the result
value = number(str, pindex); // Get the first number in the term
// Loop as long as we have a good operator
while((*(str+(*pindex))==""*"")||(*(str+(*pindex))==""/""))
{
if(*(str+(*pindex))==""*"") // If it""s multiply,
{
++(*pindex);
value *= number(str, pindex); // multiply by next number
}
if(*(str+(*pindex))==""/"") // If it""s divide,
{
++(*pindex);
value /= number(str, pindex); // divide by next number
}
}
return value; // We""ve finished, so return what we""ve got
}
// Function to recognize a number in a string
double number(char * str, int * pindex)
{
double value = 0.0; // Store the resulting value
char * psubstr; // Pointer for substring
if(*(str + (*pindex)) == ""("") // Start of parentheses
{
++(*pindex);
psubstr = extract(str, pindex); // Extract substring in brackets
value = expr(psubstr); // Get the value of the substring
return value; // Return substring value
}
while(isdigit(*(str+(*pindex)))) // Loop accumulating leading digits
value=10*value + (*(str+(*pindex)++) - 48);
// Not a digit when we get to here
if(*(str+(*pindex))!=""."") // so check for decimal point
return value; // and if not, return value
double factor = 1.0; // Factor for decimal places
while(isdigit(*(str+(++(*pindex))))) // Loop as long as we have digits
{
factor *= 0.1; // Decrease factor by factor of 10
value=value + (*(str+(*pindex))-48)*factor; // Add decimal place
}
return value; // On loop exit we are done
}
// Function to extract a substring between parentheses
// (requires string.h)
char * extract(char * str, int * pindex)
{
char buffer[MAX]; // Temporary space for substring
char * pstr = NULL; // Pointer to new string for return
int numL = 0; // Count of left parentheses found
int bufindex = *pindex; // Save starting value for index
do
{
buffer[(*pindex) - bufindex] = *(str + (*pindex));
switch(buffer[(*pindex) - bufindex])
{
case "")"":
if(numL == 0)
{
buffer[(*pindex) - bufindex] = ""\0""; // Replace "")"" with ""\0""
++(*pindex);
pstr = (char *) malloc((*pindex) - bufindex + 1);
if (!pstr)
{
printf("Memory allocation failed, program terminated.") ;
exit(1);
}
strcpy(pstr, buffer); // Copy substring to new memory
return pstr; // Return substring in new memory
}
else
numL--; // Reduce count of ""("" to be matched
break;
case ""("":
numL++; // Increase count of ""("" to be // matched
break;
}
} while(*(str + (*pindex)++) != ""\0""); // Loop - don""t overrun end of string
printf("Ran off the end of the expression, must be bad input.\n");
exit(1);
}
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平方return x*x;
三角函数：直接库函数，#include <math.c> sin() |
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這個計算器 的計算，是不是只能計算
類似於a*b+c*d这样格式的表逹式？ 對於三角函數，楼上已經說了。有對應的庫，google一下就有大把答案。 |
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再math中有好多库函数，可以利用
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原理的话
平方可以用二分法 三角函数貌似只能用级数 |
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50分 |
仅供参考：
/*---------------------------------------
函数型计算器(VC++6.0,Win32 Console)程序由 yu_hua 于2007-07-27设计完成
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∧
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。
----------------------------------------*/
#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 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;
}
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",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;
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) {
cout<< "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)) {
cout<< "两个π相连" <<endl;exit(2);
}
if (*pp==""("") {
cout<< "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 {
cout<< "陌生函数名" <<endl;exit(4);
}
}
} else if (c==""+""||c==""-""||c==""*""||c==""/""||c==""%""||c==""^"") {
char cc;
if (last != DIGIT) {
cout<< "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==""^"") {
cout<< "乘幂符连用" <<endl;exit(6);
}
op[iop++] = c;
}
last = !DIGIT;
} else {
if (last == DIGIT) {
cout<< "两数字粘连" <<endl;exit(7);
}
ST[ist++]=strtod(pp,&rexp);
ST[ist-1]=fun(ST[ist-1],op,&iop);
if (pp == rexp) {
cout<< "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) {
cout<< "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;
if (argc<2) {
if (GetConsoleOutputCP()!=936) system("chcp 936>NUL");//中文代码页
cout << "计算函数表达式的值。"<<endl<<"支持(),+,-,*,/,%,^,Pi,sin,cos,tan,sqrt,arcsin,arccos,arctan,lg,ln,exp"<<endl;
while (1) {
cout << "请输入表达式：";
gets(s);
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
cout << "计算由≥1个命令行参数给出的函数表达式的值。最后一个参数是.0～.15表示将计算结果保留小数0～15位"<<endl<<"支持(),+,-,*,/,%,^^,Pi,sin,cos,tan,sqrt,arcsin,arccos,arctan,lg,ln,exp"<<endl;
} 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 {
strncat(s,argv[a],MAXLEN-1);
printf("%.15lg\n",calc(s,&endss));
}
} else {
printf("%.15lg\n",calc(s,&endss));
}
}
return 0;
}
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前两天CSDN C/C++论坛离了zhao4zhong1这根胡萝卜还真开不了席了！
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楼主如果还想在这方面探究下去的话：
http://www.codeproject.com/Articles/286121/Compiler-Patterns 或 参考Tiny C Compiler源代码。 |
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