Replacing Morse to English

**Temphost** · 09-16-2019

Hi, working on a college project (only very new to C) and i'm trying to write a code that i input a bunch of morse into the program, but when it runs the morse is translated into english, i know i assume i have to have every morse equal to a letter or number with a space after, two spaces for a word break, then the program will check the sentence and replace each it reads with the correct given translation. I have no idea how to do this properly. The best i've done is a weird concoction that only reads the first character e.g the - or the . Any ideas?
Thanks.
-Teepee

**Temphost** · 09-16-2019

To add, sorry if i didn't use correct tags or post icons, just signed up and first post.

**Salem** · 09-16-2019

It's hard to give you more ideas, if you don't show your current idea.

Plus, it's hard to show you how without just giving you the code.

**Temphost** · 09-16-2019

This is what i did originally to try, but i don't think that breaks and cases are the right way to go with it, maybe strings or arrays?

Code:

#include <stdio.h>
    


main (){




char enterMorse = '--'; 


switch(enterMorse) {
    case '.-':
        printf("A");
    break;
    case '-...':
        printf("B");
    break;
    case '-.-.':
        printf("C");
    break;
    case '-..':
        printf("D");
    break;
    case '.':
        printf("E");
    break;
    case '..-.':
        printf("F");
    break;
    case '--.':
        printf("G");
    break;
    case '....':
        printf("H");
    break;
    case '..':
        printf("I");
    break;
    case '.---':
        printf("J");
    break;
    case '-.-':
        printf("K");
    break;
    case '.-..':
        printf("L");
    break;
    case '--':
        printf("M");
    break;
    case '-.':
        printf("N");
    break;
    case '---':
        printf("O");
    break;
    case '.--.':
        printf("P");
    break;
    case '--.-':
        printf("Q");
    break;
    case '.-.':
        printf("R");
    break;
    case '...':
        printf("S");
    break;
    case '-':
        printf("T");
    break;
    case ',,-':
        printf("U");
    break;
    case '...-':
        printf("V");
    break;
    case '.--':
        printf("W");
    break;
    case '-..-':
        printf("X");
    break;
    case '-.--':
        printf("Y");
    break;
    case '--..':
        printf("Z");
    break;
    case '-----':
        printf("0");
    break;
    case '.----':
        printf("1");
    break;
    case '..---':
        printf("2");
    break;
    case '...--':
        printf("3");
    break;
    case '....-':
        printf("4");
    break;
    case ',,,,,':
        printf("5");
    break;
    case '-....':
        printf ("6");
    break;
    case '--...':
        printf ("7");
    break;
    case '---..':
        printf ("8");
    break;
    case '----.':
        printf ("9");
    break;
    default:
        printf ("invaliddddddd");
    break;
}
 printf ("%c\n", enterMorse);




    
    system("pause");

it was just reading the first - in char entermorse

**Salem** · 09-16-2019

OK, a few things to sort out.

1. 'c' != "c"
In single quotes, you have a character constant, and it can only be a single character.
In double quotes, it's a string, and you can have as many characters as you like.
Whilst you can do switch('c'), you can't do switch("c"), so you have to resort to using strcmp.

2. Split the problem into functions.

Code:

void morse ( const char *morse ) {
    // Now you can focus on just one letter.
}

int main ( ) {
  char morse[] = ".-";
  decodeMorse(morse);
}

3. Do you know about arrays? Do you know about structures?

**laserlight** · 09-16-2019

I'm not familiar with multi-character literals, but as you discovered they don't work for you in this instance.

Rather, input the morse code as a string which you can then break up into substrings, each corresponding to a single morse code "letter". Then you have a few possible approaches, e.g., computing a unique number from the morse code.

**Temphost** · 09-16-2019

Originally Posted by Salem

3. Do you know about arrays? Do you know about structures?

I kind of know arrays, not about structures, currently doing strings and arrays in lectures and classes. Not clicking yet though

**Salem** · 09-16-2019

You save a lot of copy/paste if you can do this.

Code:

char morseTable[][6] = {
    ".-",
    // etc
};
char letterTable[][2] = {
    "A",
    // etc
};

A for loop through one of them will give you an index into the other one - when a match is found.

**Temphost** · 09-16-2019

Would the way you just showed be like this? and is the [6] and [2] how many i can have?

Code:

 char morseTable[][26] = {

Code:

    ".-", "..", "--",
    // etc
};
char letterTable[][26] = {
    "A","B", "c", "d",
    // etc
};

**Salem** · 09-16-2019

> Would the way you just showed be like this? and is the [6] and [2] how many i can have?
That's the length of each string.

char morseTable[numberOfMorseSymbols][maxLengthOfMorseCode]

But the compiler will count the left-most dimension for you, based on how many initialisers you provide.

**Structure** · 09-16-2019

only reads the first character

The problem:

'a' is for characters.
"abc" is for string.

Double quotes is for string and single quotes for character.

therefore: '--.' is invalid

**Structure** · 09-16-2019

any ideas?

Comparing strings can be difficult...

Code:

#include <stdio.h>
#include <string.h>

#define morse_A ".-"
#define morse_B "-..."
#define morse_C "-.-."
#define morse_D "-.."
#define morse_E "."
#define morse_F "..-."
#define morse_G "--."
#define morse_H "...."
#define morse_I ".."
#define morse_J ".---"
#define morse_K "-.-"
#define morse_L ".-.."
#define morse_M "--"
#define morse_N "-."
#define morse_O "---"
#define morse_P ".--."
#define morse_Q "--.-"
#define morse_R ".-."
#define morse_S "..."
#define morse_T "-"
#define morse_U "..-"
#define morse_V "...-"
#define morse_W ".--"
#define morse_X "-..-"
#define morse_Y "-.--"
#define morse_Z "--.."

char morseEntered[10];
int compare(char *string1,char *string2) {
  int response = 1;
  for (int i=0;i<=strlen(string1);i++) {
    if ( string1[i] != string2[i] ) response = 0;
  };
  return response;
};

int main(int argc, char *argv[]) {
  sprintf(morseEntered,".-");
  if ( compare(morseEntered,morse_A) ) printf("A");
  if ( compare(morseEntered,morse_B) ) printf("B");
  if ( compare(morseEntered,morse_C) ) printf("C");
  if ( compare(morseEntered,morse_D) ) printf("D");
  if ( compare(morseEntered,morse_E) ) printf("E");
  if ( compare(morseEntered,morse_F) ) printf("F");
  if ( compare(morseEntered,morse_G) ) printf("G");
  if ( compare(morseEntered,morse_H) ) printf("H");
  if ( compare(morseEntered,morse_I) ) printf("I");
  if ( compare(morseEntered,morse_J) ) printf("J");
  if ( compare(morseEntered,morse_K) ) printf("K");
  if ( compare(morseEntered,morse_L) ) printf("L");
  if ( compare(morseEntered,morse_M) ) printf("M");
  if ( compare(morseEntered,morse_N) ) printf("N");
  if ( compare(morseEntered,morse_O) ) printf("O");
  if ( compare(morseEntered,morse_P) ) printf("P");
  if ( compare(morseEntered,morse_Q) ) printf("Q");
  if ( compare(morseEntered,morse_R) ) printf("R");
  if ( compare(morseEntered,morse_S) ) printf("S");
  if ( compare(morseEntered,morse_T) ) printf("T");
  if ( compare(morseEntered,morse_U) ) printf("U");
  if ( compare(morseEntered,morse_V) ) printf("V");
  if ( compare(morseEntered,morse_W) ) printf("W");
  if ( compare(morseEntered,morse_X) ) printf("X");
  if ( compare(morseEntered,morse_Y) ) printf("Y");
  if ( compare(morseEntered,morse_Z) ) printf("Z");
  return 0;
};

**laserlight** · 09-16-2019

Originally Posted by Structure

Comparing strings can be difficult...

Code:

#include <stdio.h>
#include <string.h>

#define morse_A ".-"
#define morse_B "-..."
#define morse_C "-.-."
#define morse_D "-.."
#define morse_E "."
#define morse_F "..-."
#define morse_G "--."
#define morse_H "...."
#define morse_I ".."
#define morse_J ".---"
#define morse_K "-.-"
#define morse_L ".-.."
#define morse_M "--"
#define morse_N "-."
#define morse_O "---"
#define morse_P ".--."
#define morse_Q "--.-"
#define morse_R ".-."
#define morse_S "..."
#define morse_T "-"
#define morse_U "..-"
#define morse_V "...-"
#define morse_W ".--"
#define morse_X "-..-"
#define morse_Y "-.--"
#define morse_Z "--.."

char morseEntered[10];
int compare(char *string1,char *string2) {
  int response = 1;
  for (int i=0;i<=strlen(string1);i++) {
    if ( string1[i] != string2[i] ) response = 0;
  };
  return response;
};

int main(int argc, char *argv[]) {
  sprintf(morseEntered,".-");
  if ( compare(morseEntered,morse_A) ) printf("A");
  if ( compare(morseEntered,morse_B) ) printf("B");
  if ( compare(morseEntered,morse_C) ) printf("C");
  if ( compare(morseEntered,morse_D) ) printf("D");
  if ( compare(morseEntered,morse_E) ) printf("E");
  if ( compare(morseEntered,morse_F) ) printf("F");
  if ( compare(morseEntered,morse_G) ) printf("G");
  if ( compare(morseEntered,morse_H) ) printf("H");
  if ( compare(morseEntered,morse_I) ) printf("I");
  if ( compare(morseEntered,morse_J) ) printf("J");
  if ( compare(morseEntered,morse_K) ) printf("K");
  if ( compare(morseEntered,morse_L) ) printf("L");
  if ( compare(morseEntered,morse_M) ) printf("M");
  if ( compare(morseEntered,morse_N) ) printf("N");
  if ( compare(morseEntered,morse_O) ) printf("O");
  if ( compare(morseEntered,morse_P) ) printf("P");
  if ( compare(morseEntered,morse_Q) ) printf("Q");
  if ( compare(morseEntered,morse_R) ) printf("R");
  if ( compare(morseEntered,morse_S) ) printf("S");
  if ( compare(morseEntered,morse_T) ) printf("T");
  if ( compare(morseEntered,morse_U) ) printf("U");
  if ( compare(morseEntered,morse_V) ) printf("V");
  if ( compare(morseEntered,morse_W) ) printf("W");
  if ( compare(morseEntered,morse_X) ) printf("X");
  if ( compare(morseEntered,morse_Y) ) printf("Y");
  if ( compare(morseEntered,morse_Z) ) printf("Z");
  return 0;
};

Assuming the compiler manages to identify that the strlen call in the loop condition is effectively a loop constant, this code has a similiar time complexity to what Salem suggested in post #8, except that it is inferior because of all that need to repeat the if statements instead of just using a loop.

Note that you should use the standard strcmp (and family) instead of writing your own string comparison function(s) unless you have special reasons to do so.

**Structure** · 09-16-2019

you should use the standard strcmp (and family) instead of writing your own string comparison function(s) unless you have special reasons to do so.

because i like to party.

**Hodor** · 09-17-2019

Originally Posted by Structure

Comparing strings can be difficult...

Code:

#include <stdio.h>
#include <string.h>

#define morse_A ".-"
#define morse_B "-..."
#define morse_C "-.-."
#define morse_D "-.."
#define morse_E "."
#define morse_F "..-."
#define morse_G "--."
#define morse_H "...."
#define morse_I ".."
#define morse_J ".---"
#define morse_K "-.-"
#define morse_L ".-.."
#define morse_M "--"
#define morse_N "-."
#define morse_O "---"
#define morse_P ".--."
#define morse_Q "--.-"
#define morse_R ".-."
#define morse_S "..."
#define morse_T "-"
#define morse_U "..-"
#define morse_V "...-"
#define morse_W ".--"
#define morse_X "-..-"
#define morse_Y "-.--"
#define morse_Z "--.."

char morseEntered[10];
int compare(char *string1,char *string2) {
  int response = 1;
  for (int i=0;i<=strlen(string1);i++) {
    if ( string1[i] != string2[i] ) response = 0;
  };
  return response;
};

int main(int argc, char *argv[]) {
  sprintf(morseEntered,".-");
  if ( compare(morseEntered,morse_A) ) printf("A");
  if ( compare(morseEntered,morse_B) ) printf("B");
  if ( compare(morseEntered,morse_C) ) printf("C");
  if ( compare(morseEntered,morse_D) ) printf("D");
  if ( compare(morseEntered,morse_E) ) printf("E");
  if ( compare(morseEntered,morse_F) ) printf("F");
  if ( compare(morseEntered,morse_G) ) printf("G");
  if ( compare(morseEntered,morse_H) ) printf("H");
  if ( compare(morseEntered,morse_I) ) printf("I");
  if ( compare(morseEntered,morse_J) ) printf("J");
  if ( compare(morseEntered,morse_K) ) printf("K");
  if ( compare(morseEntered,morse_L) ) printf("L");
  if ( compare(morseEntered,morse_M) ) printf("M");
  if ( compare(morseEntered,morse_N) ) printf("N");
  if ( compare(morseEntered,morse_O) ) printf("O");
  if ( compare(morseEntered,morse_P) ) printf("P");
  if ( compare(morseEntered,morse_Q) ) printf("Q");
  if ( compare(morseEntered,morse_R) ) printf("R");
  if ( compare(morseEntered,morse_S) ) printf("S");
  if ( compare(morseEntered,morse_T) ) printf("T");
  if ( compare(morseEntered,morse_U) ) printf("U");
  if ( compare(morseEntered,morse_V) ) printf("V");
  if ( compare(morseEntered,morse_W) ) printf("W");
  if ( compare(morseEntered,morse_X) ) printf("X");
  if ( compare(morseEntered,morse_Y) ) printf("Y");
  if ( compare(morseEntered,morse_Z) ) printf("Z");
  return 0;
};

Your compare function still has undefined behaviour if the length of string1 is longer than string2's length (because would be reading/comparing beyond the end of string2). Try adding a break.

For example:

Code:

int compare(char *string1,char *string2) {
  int response = 1;
  for (int i=0;i<=strlen(string1);i++) {
    if ( string1[i] != string2[i] ) {
         response = 0;
         break;
    }
  };
  return response;
};

At least it will work now even though you're relying on the compiler to make the assumption that the strlen() call is invariant for the loop. Assuming it does it's not really the most obvious way to write a function that compares strings.
The is at least one other problem: string1 and string2 not const qualified (i.e. the function prototype should really be int compare(const char *string1, const char *string2)). Another potential problem is the return value which is, for example, different to what the standard function strcmp() would return. If you really want or need the return value to be either 0 or 1 and nothing else why not write !!strcmp(morseEntered,morse_A). I can't see the point of this compare() function

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