C++ Calculator Sample Program

// calcltr.cpp
//
// Calculator program that runs in console.
// Type M for menu.
//
// This is the original from PSW book Using C++
// I have used it as a basis to learn C++
//
// I have kept is at the following modifications will
// be easier to understand as the program becomes more sophisticated.
//
// Planned mods
// 01 Change command short cuts to alpha characters so that they are simple to
// key. Trivial change.
// 02 Add extra functions again trivial.
// 03 Add Memory functions
// MEM IN .. loads memory with current value
// MEM PLUS .. adds current value to memory
// Note: Mem Minus achieved by typing n (negative) to make current
// value negative and MEM PLUS. If required redo n to make current
// value positive.
// MEM SWITCH switches current value and memory.
// 04 Add cacpability to use mem value in function, e.g. to subtract value in
// in memory from current value, but keep memory value.
// This was a bit complicated and required writing function to replace CIN
// and use of STRING to DOUBLE function
// 05 Improve by checking that values entered are numbers and not garbage.
// 06 Capability to undo up to last 5 commands. Code with Vector?
// 07 Log comands to file so that they can be audited.
// Have default log KALKLOG.DAT in C:|MyDATA which is backed up to
// KALKLOG.BAK start of new program, overwriting previous version.
// 08 Allow user to change log file name and locaton.
// 09 Take data file in LOG format and run as batch program.
//
// Also plan to use as test for compiling in Linux and with other systems.
// May try to convert to Java and Ruby??
// When I have learned widows programming may try to convert to windows type.
//
// I know it is all old hat but it helps me to learn and may even help others.
//

#include
#include
#include
#include
using namespace std;

void display_menu();
int is_menu_choice(char choice);
void process_choice (char choice, // IN
double& curr_val); // IN-OUT
int main()
{
char choice; // menu choice
double curr_val; // current value of calculator

display_menu();
cout << setprecision(15);
curr_val = 0;
do {
cin >> choice;
choice = toupper(choice);
process_choice (choice, curr_val);
}
while (choice != 'Q');
return 0;
}

void display_menu()
{
cout << "Calculator functions:\n"
<< " +(add), *(mult), ^(expo),\n"
<< " (I)nvert, (S)et, (Q)uit,\n"
<< " show this (M)enu again.\n\n";
}

int is_menu_choice(char choice)
{
switch (choice)
{
case '+': case '*': case '^':
case 'I': case 'S': case 'Q':
case 'M':
return 1;
default:
return 0;
} // end switch
}

void process_choice (char choice, // IN
double& curr_val) // IN-OUT
{
double num;
switch (choice)
{
case '+': cin >> num;
curr_val += num;
break;
case '*': cin >> num;
curr_val *= num;
break;
case '^': cin >> num;
curr_val = pow(curr_val, num);
break;
case 'I': curr_val = 1/curr_val;
break;
case 'M': break;
case 'Q': break;
case 'S': cin >> curr_val;
break;
default: cout << "\tInvalid operation!\n";
} // end switch
if (choice=='M') display_menu();
if (choice != ('Q' || 'M' ))
cout << setw(16) << ' ' << curr_val
<< endl;
}

/* A typical run:
Calculator functions:
+(add), *(mult), ^(expo),
(I)nvert, (S)et, (Q)uit,
show this (M)enu again.

S 2.5
2.5
^ 3
15.625
I
0.064
* 100
6.4
q
*/