English to Morse code converter

Question

I need to convert English letters and Arabic numbers to Morse code until enter is pressed. I used a do while loop to read letters until enter is pressed.

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
using namespace std;

int j = 0;
char a[100];
const char *latin = "**ETIANMSURWDKGOHVF?L?PJBHCYZQ??54?3??2?????6????7??890";

void dash(){cout<<"-";}
void dot(){cout<<".";}

void conv(int decimal)
{
   if(decimal){
    conv(decimal/2);
    if(decimal!=1) decimal%2 ? dash() : dot();
   }
}

void morse(char a[], int lenght)
{
    for(int i = 0; i <= lenght; i++)
    {
        if(a[i] >= 'a' && a[i] <= 'z') a[i] -= 32;
        if(a[i] < 'A' && a[i] > 'Z') return;
        while(latin[++j] != a[i]);
            conv(j);

    }
}

int main()
{
    int lenght = 0;

    cout<<"letter=";

   do{
        cin>>a[lenght];
        lenght++;
    } while(0);


    morse(a, lenght);

    return 0;
}

When I return the length it is always one, so the function makes only one loop. Also, there are some extra symbols that appear when the code is compiled.

Answer 1

There are a few things going on here, but the reason that lenght is always 1 is because you only run through your while loop once:

do {
    cin>>a[lenght];
    lenght++;
} while (0); // this will always evaluate to false

The do block above only executes once because while (0) evaluates to false. This means that lenght is only incremented once, which would explain why its value is 1.

Here's a (potentially) better way:

while (cin.peek() != '\n') {
  cin >> a[lenght++];
}

And you can get the output you're looking for by modifying main():

int main()
{
    int length = 0;

    cout << "letter = ";

    while (cin.peek() != '\n') {
      cin >> a[length++];
    }

    int i = 0;
    while (i < length) {
      morse(a[i]);
      i++;
    }
    cout << endl;

    return 0;
}

Code

Here it is all assembled (along with a few minor changes to conv() and morse()):

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
using namespace std;

int j = 0;
char a[100];
const char *latin = "**ETIANMSURWDKGOHVF?L?PJBHCYZQ??54?3??2?????6????7??890";

void dash(){cout<<"-";}
void dot(){cout<<".";}

void conv(int decimal) {
    if (decimal) {
        conv(decimal/2);
        if (decimal != 1) decimal%2 ? dash() : dot();   
    } 
}

void morse(char c) {
    if (c >= 'a' && c <= 'z') c -= 32;
    if (c < 'A' || c > 'Z') return;
    int i = 0;
    while (latin[++i] != c);
    conv(i);
}

int main()
{
    int length = 0;

    cout << "letter = ";

    while (cin.peek() != '\n') {
      cin >> a[length++];
    }

    int i = 0;
    while (i < length) {
      morse(a[i]);
      i++;
    }
    cout << endl;

    return 0;
}

Input

$ letter = sos

Output

$ ...---...

Edit

As pointed out by user4581301 below, this can be simplified further by removing a[] and the second loop:

int main()
{
    int length = 0;
    char c;

    cout << "letter = ";

    while (cin.peek() != '\n') {
      char c;
      cin >> c;
      morse(c);
    }
    cout << endl;

    return 0;
}