Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
Desktop Calculator is a application coded in Standard C++. It is a application based on the example 6.1 in the book "The C++ Programming Language", Third Edition by Bjarne Stroustrup.
/*
* This file is part of Desktop Calculator.
*
* Desktop Calculator is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Desktop Calculator is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* Standard
* You should have received a copy of the GNU General Public License
* along with Desktop Calculator. If not, see < http://www.gnu.org/licenses/ >.
*
* Shishir Sharma < shishirsharma.in AT gmail DOT com >
*/
//////////////////////////////////////////////////////////
// //
// File name : dc //
// Comments : desk calculator //
// Versions : Saturday, September 23, 2006 //
// Coded by : Shishir Sharma 'C R I S S' //
// shishirsharma.in [at] gmail.com //
// //
//////////////////////////////////////////////////////////
/*
How to compile
$ gcc dc.cpp -o dc -lstdc++
*/
#include <iostream>
#include <string>
#include <map>
#include <cctype>
#include <cmath>
using namespace std;
enum Token_value {
FUNCTION, NAME, NUMBER, END,
PLUS = '+', MINUS = '-', MUL = '*', DIV = '/',
PRINT = ';', ASSIGIN = '=', LP = '(', RP = ')',
EXPO = '^', MLP = '[', MRP = ']', COMMA = ','
};
Token_value curr_tok = PRINT;
double number_value;
string string_value;
int no_of_errors;
map < string, double > table;
double error (const string & s);
double message (const string & s);
Token_value get_token ();
double prim (bool get);
double term (bool get);
double expr (bool get);
const char help[] = "DC: Desk Calculator\n\npress ctrl+Z to quit\n";
int
main (int argc, char *argv[])
{
// Standard variables
table["pi"] = 3.1415926535897932385;
table["e"] = 2.7182818284590452354;
// Default help message
message (help);
// Main loop
while (cin) {
get_token ();
if (curr_tok == END)
break;
if (curr_tok == PRINT)
continue;
cout << expr(false) << '\n';
}
return no_of_errors;
}
double
message (const string & s)
{
cout << s << '\n';
return 0;
}
double
error (const string & s)
{
no_of_errors++;
cerr << "Error:" << s << '\n';
return 1;
}
double
expr (bool get)
{
double left = term (get);
for (;;)
switch (curr_tok) {
case PLUS:
{
left += term (true);
break;
}
case MINUS:
{
left -= term (true);
break;
}
default:
return left;
}
}
double
term (bool get)
{
double left = prim (get);
for (;;)
switch (curr_tok) {
case MUL: {
left *= term (true);
break;
}
case DIV: {
if (double d = prim (true)) {
left /= d;
break;
}
return error ("divide by 0");
}
case EXPO: {
left = pow (left, prim (true));
break;
}
default:
return left;
}
}
double
prim (bool get)
{
if (get)
get_token ();
switch (curr_tok) {
case MINUS: {
return (-expr (true));
}
case NUMBER: {
double v = number_value;
get_token ();
return v;
}
case NAME: {
//help
if (string_value == "help" || string_value == "Help"
|| string_value == "HELP") {
return message (help);
}
else if (string_value == "clear" || string_value == "Clear"
|| string_value == "CLEAR") {
cout.flush ();
return message (help);
}
else
//trignometry functions
if (string_value == "sin") {
if (get_token () == LP)
return sin (expr (true));
}
else if (string_value == "cos") {
if (get_token () == LP)
return cos (expr (true));
}
else if (string_value == "tan") {
if (get_token () == LP)
return tan (expr (true));
}
else if (string_value == "asin") {
if (get_token () == LP)
return asin (expr (true));
}
else if (string_value == "acos") {
if (get_token () == LP)
return acos (expr (true));
}
else if (string_value == "atan") {
if (get_token () == LP)
return atan (expr (true));
}
// exponential functions
else if (string_value == "exp") {
if (get_token () == LP)
return exp (expr (true));
}
else if (string_value == "log") {
if (get_token () == LP)
return log (expr (true));
}
else if (string_value == "log10") {
if (get_token () == LP)
return log10 (expr (true));
}
else if (string_value == "sum") {
get_token ();
if (curr_tok == LP) {
double sum = 0;
sum += expr (true);
while (curr_tok != RP) {
if (curr_tok == COMMA)
sum += expr (true);
}
return sum;
}
}
// new variables
else {
double &v = table[string_value];
if (get_token () == ASSIGIN)
v = expr (true);
return v;
}
}
case LP: {
double e = expr (true);
if (curr_tok != RP)
return error ("')' expected");
get_token ();
return e;
}
default:
return error ("primary expected");
}
}
Token_value
get_token ()
{
char ch;
do {
if (!cin.get (ch))
return curr_tok = END;
} while (ch != '\n' && isspace (ch));
switch (ch) {
case '\n':
case ';':
return curr_tok = PRINT;
case '^':
case '*':
case '/':
case '+':
case '-':
case '(':
case ')':
case '[':
case ']':
case ',':
case '=':
return curr_tok = Token_value (ch);
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
case '.':
cin.putback (ch);
cin >> number_value;
return curr_tok = NUMBER;
default:
if (isalpha (ch)) {
string_value = ch;
while (cin.get (ch) && isalnum (ch))
string_value.push_back (ch);
cin.putback (ch);
return curr_tok = NAME;
}
error ("bad token");
return curr_tok = PRINT;
}
}
/* eof */
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment