patterncppMinor

Simple mathematical console application

Submitted by: @import:stackexchange-codereview·Mar 10, 2026·

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consolesimplemathematicalapplication

Problem

I am new to C++ and with my basic knowledge of the language, I have attempted to create a simple console application filled with lots of useful functions involving math related stuff.

The following is the only version of it that I have created thus far: (also available here).

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

string cmd;
bool moduleRun = true;

//Decorations
void finline(string appName){cout> n1 >> op >> n2;
switch(op){
//case '%' :
case '+' : cout' : (n1>n2)?cout> ";
cin>>arr[i];
total+=arr[i];
}
return total;
}

long double mean(int n){ return ( sum(n) / n ); }

long double prod(int n){
int arr[n];
long double product = 1;
for(int i = 0; i> ";
cin>>arr[i];
product*=arr[i];
}
cout> func >> param;
//Trigo
if(func == "sin") cout>n>>u1;
cout>u2;
if(u1 == u2){cout> ";
cin>>a;
cout> ";
cin>>b;
cout> ";
cin>>c;
double d = pow(b,2) - (4ac);
if( d >ans;
switch(sel){
case 0:
if( ans == (a + b) ){ cout100){
if(score>=50){cout> cmd;
if(cmd == "n" || cmd == "no"){cout>guess;
tries++;
if(guess>number){cout>cmd;
if( cmd =="n" || cmd =="no"){gameRun = false;} //ends game loop
else{ cout";
cin>>cmd;
if(cmd == "guessthenumber"){ guessthenumber(); }
else if(cmd == "solve"){ solve(); }
else if(cmd=="exit" || cmd =="quit"){ moduleRun = false; }
else{cout>";
cin >> cmd;
if( cmd == "cmdlist" || cmd=="commands" ){
cout << "\n\tcalc - Starts Arithmetic Calculator\n\tconv - Convert values to different units\n\tfunc - Scientific functions including sin, cos & tan\n\tquad - Finds the roots of a Quadratic Equation of the form ax^2 + bx + c = 0\n\tgames - Activates the games module\n\n";
}
else if( cmd == "calc" || cmd == "ca

Solution

The command pattern is your friend.

You can then use a std::map to convert a user input string to a command during execution.

#include 
#include 
#include 
#include 
#include 

int main(int argc, char* argv[])
{
    std::map>    commands;

    commands["sin"] = [](double d) {return std::sin(d);};
    commands["cos"] = [](double d) {return std::cos(d);};
    //... etc.

    std::string command = argv[1];
    double      value   = std::atof(argv[2]);
    std::cout << commands[command](value) << "\n";
}

Your conversions can be done by a matrix:

Unit
              m   c      d     h     k
   mili       0   1     2      3     4     5
   cente     -1   0     1      2     3     4
       -2  -1     0      1     2     3
   deca      -3  -2    -1      0     1     2
   hecto     -4  -3    -2     -1     0     1
   kilo      -5  -4    -3     -2    -1     0

So the table above defines the power conversion from one unit to another.

int conversion[6][6] = {{0,1,2,3,4,5}, {-1,0,1,2,3,4}, .... };
   std::map  data = {{ "m", 0 }, {"c", 1}, {"", 2}, {"d", 3}, {"h", 4}, {"k", 5}};

   std::string srcType  = "d";  // src deca
   std::string dstType  = "k";  // kilo
   int   src = data[srcType];
   int   dst = data[dstType];
   int result = n * pow(10, conversion[src][dst]);

Code Snippets

#include <map>
#include <string>
#include <functional>
#include <cmath>
#include <iostream>

int main(int argc, char* argv[])
{
    std::map<std::string, std::function<double(double)>>    commands;

    commands["sin"] = [](double d) {return std::sin(d);};
    commands["cos"] = [](double d) {return std::cos(d);};
    //... etc.

    std::string command = argv[1];
    double      value   = std::atof(argv[2]);
    std::cout << commands[command](value) << "\n";
}

Unit
              m   c   <none>   d     h     k
   mili       0   1     2      3     4     5
   cente     -1   0     1      2     3     4
   <none>    -2  -1     0      1     2     3
   deca      -3  -2    -1      0     1     2
   hecto     -4  -3    -2     -1     0     1
   kilo      -5  -4    -3     -2    -1     0

int conversion[6][6] = {{0,1,2,3,4,5}, {-1,0,1,2,3,4}, .... };
   std::map<std::string, int>  data = {{ "m", 0 }, {"c", 1}, {"", 2}, {"d", 3}, {"h", 4}, {"k", 5}};

   std::string srcType  = "d";  // src deca
   std::string dstType  = "k";  // kilo
   int   src = data[srcType];
   int   dst = data[dstType];
   int result = n * pow(10, conversion[src][dst]);

Context

StackExchange Code Review Q#31813, answer score: 7

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