C + + Implementation Simple Calculator (regular expression calculation)

Description: Simple and efficient C + + code to implement a simple calculator (regular expression calculation), allowing decimals, parentheses. But there is no right-and-wrong test function, so make sure you are correct before testing.

Data structure: Stack

Demonstration Input:

((1.5+2.5) *3-4) +5

42/7-(12+3) *0.5

Standard output:

The answer is 13

The answer is-1.5

Source:

#include <iostream>
#include<stack>using namespaceStd;stack<Double> numbers;//number of storage operationsstack<Char> Operations;//Storage Operators/*prioritize operators with ' # ' as the operations of the stack (for later operation)*/intPriorityCharoperate) {    Switch(operate) { Case '#': Case '\ n':return 0;  Case '(': Case ')':return 1;  Case '+': Case '-':return 2;  Case '*': Case '/':return 3; }}voidCalculateChar);intMain () {cout<<"WELCOME CALCULATOR"<< Endl <<Endl<<"input an Algebrais expression to calculate or input ' Q ' to quit"<< Endl <<Endl; CharCommand = cin.Get();  while(Command! ='Q') {Calculate (command); Command= cin.Get(); }    return 0;}voidCalculateCharcommand) {    Doublenum, Leftnum, rightnum, result; Switch(command) {/*if the input is a number, the data of the double type is stored in the stack*/     Case '0': Case'1': Case '2': Case'3': Case '4': Case'5': Case '6': Case'7': Case '8': Case'9': Cin.putback (command); CIN>>num;        Numbers.push (num);  Break;  Case '(': Case ')': Case '+': Case '-': Case '*': Case '/': Case '\ n':        /*initialize the stack bottom element as ' # '*/        if(Operations.empty ()) Operations.push ('#'); /*If you now enter an operator with a higher precedence or input ' (', you should store the current operator and do not perform the previous operator*/        if(Command > Priority (Operations.top ()) | | command = ='(') operations.push (command); /*if the previously entered operator precedence is higher, the previous operator should be executed*/        Else {             while(command) <=Priority (Operations.top ())) {                /*when the operator is fully implemented, expose the stack bottom element ' # ' and enter ' \ n ' to print the result*/                if(Operations.top () = ='#'&& Command = ='\ n') {result=Numbers.top (); cout<<"The answer is"<< result << Endl <<Endl;                    Numbers.pop ();                    Operations.pop ();  Break; }                /*when the parentheses inside the operator are fully implemented, the parentheses are removed, and the next character is read into*/                Else if(Operations.top () = ='('&&command = =')') {operations.pop (); CIN>>command; }                /*In either case, the previous operator, Operations.top () , is completed*/                Else{rightnum=Numbers.top ();                    Numbers.pop (); Leftnum=Numbers.top ();                    Numbers.pop (); Switch(Operations.top ()) { Case '+': Numbers.push (Leftnum+rightnum);                        Operations.pop ();  Break;  Case '-': Numbers.push (Leftnum-rightnum);                        Operations.pop ();  Break;  Case '*': Numbers.push (Leftnum*rightnum);                        Operations.pop ();  Break;  Case '/': Numbers.push (Leftnum/rightnum);                        Operations.pop ();  Break; }                }            }            /*once the previous high-priority operation is completed, the current operator (other than ' \ n ') becomes the highest priority, so it should be stored*/            if(command!='\ n') operations.push (command); }         Break; }}

C + + Implementation Simple Calculator (regular expression calculation)