Created
September 18, 2014 09:08
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Строковый калькулятор С++
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#include "stdafx.h" | |
#include <iostream> | |
#include <iomanip> | |
double number(); | |
double factor(); | |
double expr(); | |
double brackets(); | |
int main() | |
{ | |
double n; | |
setlocale(LC_ALL, "Rus"); | |
std::cout << "Введите выражение: "; | |
n = expr(); | |
std::cout << "Результат вычисления: " << std::setprecision(8) << n << std::endl; | |
std::cin.get(); | |
return 0; | |
} | |
double number() | |
{ | |
double result = 0.0; | |
double k = 10.0; | |
int sign = 1; | |
char c; | |
c = std::cin.get(); | |
while (c == ' ') | |
c = std::cin.get(); | |
if (c == '-') | |
sign = -1; | |
else | |
std::cin.putback(c); | |
while (true) | |
{ | |
c = std::cin.get(); | |
while (c == ' ') | |
c = std::cin.get(); | |
if (c >= '0' && c <= '9') | |
result = result * 10.0 + (c - '0'); | |
else | |
{ | |
std::cin.putback(c); | |
break; | |
} | |
} | |
c = std::cin.get(); | |
if (c == '.') | |
{ | |
while (true) | |
{ | |
c = std::cin.get(); | |
if (c >= '0' && c <= '9') | |
{ | |
result += (c - '0') / k; | |
k *= 10.0; | |
} | |
else | |
{ | |
std::cin.putback(c); | |
break; | |
} | |
} | |
} | |
else | |
std::cin.putback(c); | |
return sign * result; | |
} | |
double factor() | |
{ | |
double result = brackets(); | |
double temp; | |
char c; | |
while (true) | |
{ | |
c = std::cin.get(); | |
while (c == ' ') | |
c = std::cin.get(); | |
switch (c) | |
{ | |
case '*': | |
result *= brackets(); | |
break; | |
case '/': | |
temp = brackets(); | |
if (temp == 0.0) | |
{ | |
std::cout << "Деление на нуль!" << std::endl; | |
exit(-1); | |
} | |
result /= temp; | |
break; | |
default: | |
std::cin.putback(c); | |
return result; | |
} | |
} | |
} | |
double expr() | |
{ | |
double result = factor(); | |
char c; | |
while (true) | |
{ | |
c = std::cin.get(); | |
while (c == ' ') | |
c = std::cin.get(); | |
switch (c) | |
{ | |
case '+': | |
result += factor(); | |
break; | |
case '-': | |
result -= factor(); | |
break; | |
default: | |
std::cin.putback(c); | |
return result; | |
} | |
} | |
} | |
double brackets() | |
{ | |
double result; | |
int sign = 1; | |
char c; | |
c = std::cin.get(); | |
while (c == ' ') | |
c = std::cin.get(); | |
if (c == '-') | |
{ | |
sign = -1; | |
c = std::cin.get(); | |
} | |
while (c == ' ') | |
c = std::cin.get(); | |
if (c == '(') | |
{ | |
result = sign * expr(); | |
c = std::cin.get(); | |
if (c != ')') | |
{ | |
std::cout << "Неверная расстановка скобок!" << std::endl; | |
exit(-1); | |
} | |
return result; | |
} | |
else | |
{ | |
std::cin.putback(c); | |
return sign * number(); | |
} | |
} |
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