help with simple :)

[Mike Garber]

>>I am trying to make a menu for my programming class and i'm having trouble making it compile, can someone help me??<<

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

int main(void)
{
    int num_trains, max_train_length, track_length, train_length;
    int avail_track_for_trains, avail_small_cars, small_cars, num_people;
    int true_train_cars, true_train_length, amount_of_trains;
    int tl, max_track, win_people, n_cars, max_tl;
    int best_car, c_car_length;
    int n, repeat, i;
    char str1[50], str2[50];
    
    printf("Type in which choice you want: 1, 2, 3, or 4");
    scanf("%d" , &n);
    
    while(n!=4)
    {
               if(n==1)
               {
                       int main(void)
{
    int num_trains, max_train_length, track_length, train_length;
    int avail_track_for_trains, avail_small_cars, small_cars, num_people;
    int true_train_cars, true_train_length, max_track_length, amount_of_trains;
       
   //Ask for user input. Max track length and max train length
    printf("What is the total length of the track?\n");
    scanf("%d" , &track_length);
   
    printf("What is the maximum length you want the trains to be?\n");
    scanf("%d" , &max_train_length);
    
   //Calculations
    avail_track_for_trains = track_length*.25;
   
    small_cars = (max_train_length-10)/8;
   
    true_train_cars = small_cars+1;
   
    true_train_length = small_cars*8+10;
   
    amount_of_trains = avail_track_for_trains/true_train_length;
   
    num_people = true_train_cars*amount_of_trains*4;
    
   
   //Display results
    printf("You can fit %d people on your trains.\n" , num_people);
    getchar();
    while(getchar()!='\n');
    return 0;
}
               }
               
               else if(n==2)
               {
                    int main(void)
{
    int tl, num_people, max_track, win_people, n_cars, max_tl, num_trains;
    int best_car, c_car_length;
   
    float ratio_array[1000], ratio;
   
    n_cars=0;
    win_people=0;
    
    //Prompt user for maximum train length and maximum track length
    printf("What is the maximum track length?\n");
    scanf("%d" , &max_track);
   
    printf("What is the maximum train length?\n");
    scanf("%d" , &max_tl);
   
   //Run through all possible train combinations
    for(tl=10; tl<=max_tl; tl+=8)
    {
        n_cars++;
        num_trains=(.25*max_track)/tl;
        num_people=n_cars*num_trains*4;
       
        if(num_people>win_people)
        {
            win_people=num_people;
            best_car=n_cars;
        }
        c_car_length=tl*num_trains;
        ratio=(1.0*num_people)/c_car_length;
        ratio_array[n_cars-1]=ratio;
    }
   
   //Display Results
    printf("You can fit %d people on your trains with %d "
           "cars per train.\n" , win_people, best_car);
   
    printf("Your ratio is %f.\n" , ratio);
    
    getchar();
    while(getchar()!='\n')
    return 0;
}
               }
               
               else if(n==3)
               {
                    int main(void)
{
    int n, repeat, i;
    char str1[50], str2[50];
    
    //Prompt user for strings for repeat test
    printf("How many times do yoo want your program to run?\n");
    scanf("%d" , &n);
    
    printf("What are the %d last names you want to check for repeats?\n" , n);
    scanf("%s" , str1);
    
    //Set Flag
    repeat=0;
    
    //Compare string 1 with the rest of the strings
    for(i=1; i<=n-1; i++)
    {
             scanf("%s" , str2);
             
             if(strcmp(str1, str2)==0)
                             repeat=1;
    }
    
    //Display Output
    if(repeat==1)
    printf("Your first word repeats.\n");
     
    else
    printf("Your first word doesnt repeat.\n");
    
    while(getchar()!='n');
    getchar();
    return 0;
}

[MutantJohn]

One thing, calling int main(void) in your code is actually you trying to re-define your main program.

Instead, just use

main();

to recursively call your main function. Or if you want, because main returns an int, you can use something like

if (!main()) { /* Code goes here */ }

and that way you can have a form of error handling.

[hk_mp5kpdw]

You should not be recursively calling your main function at all.

You need to be using looping mechanisms to display the menu and process the user input.

[anduril462]

@Mike Garber
Your indentation needs work. It's hard for me to figure out which loops and if statements are inside what other loops and if statements. If it's hard to read your code, it's easy to make mistakes and hard to find or fix them. Good indentation/formatting is one of the easiest ways to make your life as a programmer (and ours helping you) much easier.

Don't use magic numbers. Instead, #define some constants.

You should be careful about redefining all those variables. Any variables you declared, e.g. on lines 24-26, "shadow" any variables by the same name that you declared on lines 7-13. To elaborate, when you read track_lenth on line 30, it changes the track_length you defined on line 24, but NOT the one you defined on line 7.

Can you narrow down the compilation problem? Maybe provide error messages and line numbers (copy-pasted so they're exact, please)? You should not have written 141 lines before you tried compiling. Come up with a plan (with paper and pencil) and test your plan. Once that's done, start coding. Write small bits (5-10 lines), compile, fix all errors and warnings (make sure your compiler is set to max warning level), and test that bit of code. That helps you localize and track down any compilation issues.

Approach this in a logical, compartmentalized fashion. Start with a function to get a menu choice. The first thing it does is just print the menu. Get that working. Then read the user input. Get that working. Then validate the user input: was it an integer? Was it between 1-4 inclusive? If not, inform the user and re-ask them for input. Hopefully you get the idea.

You should also try to break your code up into functions. When you have sections of repeated code, move it into a function. That will give you only one place to make/find/fix a mistake, plus it will shorten your code, turning several lines into a one-line function call. Along with sections of repeated code, you should break up long sections of code into functions that are smaller and more maintainable. I use a "one screenful" rule of thumb, so basically I try to keep functions to around 50-75 lines.

[Salem]

A development process
I'm wondering how much typing you did before spotting that the edifice you were creating didn't stand a cat in hells chance of compiling, never mind running.

You can't just write 100's of lines of code off the bat, then dump it on a forum for someone else to fix.

Start again, and take it SLOW. Write a few lines and compile. Do NOT add more code if what you just wrote fails to compile.
Every few iterations, make sure the code runs within the limits of what you expect to happen.

[SirPrattlepod]

Try breaking the code up into functions :/

[Mike Garber]

I have 3 programs in int main(void and they all work.. All I want to do now is print out a menu to choose program1, program2, program3, or 4quit by using if statements to run parts if my code.. I still need help I dont know why they will all work individually but not together in if statements..

This one works fine. (Choice 1):

#include<stdio.h>
#include<stdlib.h>

int main(void)
{
    int num_trains, max_train_length, track_length, train_length;
    int avail_track_for_trains, avail_small_cars, small_cars, num_people;
    int true_train_cars, true_train_length, max_track_length, amount_of_trains;
       
   //Ask for user input. Max track length and max train length
    printf("What is the total length of the track?\n");
    scanf("%d" , &track_length);
   
    printf("What is the maximum length you want the trains to be?\n");
    scanf("%d" , &max_train_length);
    
   //Calculations
    avail_track_for_trains = track_length*.25;
   
    small_cars = (max_train_length-10)/8;
   
    true_train_cars = small_cars+1;
   
    true_train_length = small_cars*8+10;
   
    amount_of_trains = avail_track_for_trains/true_train_length;
   
    num_people = true_train_cars*amount_of_trains*4;
    
   
   //Display results
    printf("You can fit %d people on your trains.\n" , num_people);
    getchar();
    while(getchar()!='\n');
    return 0;
}

This one works fine. (Choice 2):

#include<stdio.h>
#include<stdlib.h>

int main(void)
{
    int tl, num_people, max_track, win_people, n_cars, max_tl, num_trains;
    int best_car, c_car_length;
   
    float ratio_array[1000], ratio;
   
    n_cars=0;
    win_people=0;
    
    //Prompt user for maximum train length and maximum track length
    printf("What is the maximum track length?\n");
    scanf("%d" , &max_track);
   
    printf("What is the maximum train length?\n");
    scanf("%d" , &max_tl);
   
   //Run through all possible train combinations
    for(tl=10; tl<=max_tl; tl+=8)
    {
        n_cars++;
        num_trains=(.25*max_track)/tl;
        num_people=n_cars*num_trains*4;
       
        if(num_people>win_people)
        {
            win_people=num_people;
            best_car=n_cars;
        }
        c_car_length=tl*num_trains;
        ratio=(1.0*num_people)/c_car_length;
        ratio_array[n_cars-1]=ratio;
    }
   
   //Display Results
    printf("You can fit %d people on your trains with %d "
           "cars per train.\n" , win_people, best_car);
   
    printf("Your ratio is %f.\n" , ratio);
    
    getchar();
    while(getchar()!='\n')
    return 0;

And this one works fine (choice 3):

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

int main(void)
{
    int n, repeat, i;
    char str1[50], str2[50];
    
    //Prompt user for strings for repeat test
    printf("How many times do yoo want your program to run?\n");
    scanf("%d" , &n);
    
    printf("What are the %d last names you want to check for repeats?\n" , n);
    scanf("%s" , str1);
    
    //Set Flag
    repeat=0;
    
    //Compare string 1 with the rest of the strings
    for(i=1; i<=n-1; i++)
    {
             scanf("%s" , str2);
             
             if(strcmp(str1, str2)==0)
                             repeat=1;
    }
    
    //Display Output
     if(repeat==1)
     printf("Your first word repeats.\n");
     
     else
     printf("Your first word doesnt repeat.\n");
     
     while(getchar()!='n');
     getchar();
     return 0;
}

But together they fail inside if statements. How come?

[anduril462]

What's stopping you from renaming main in each of those programs to something else that actually describes what the function does, then putting them all in one file and calling them from that file's main function, which contains just your simple menu code and a switch/if-else if statement? Don't try to mash it all into some giant, ugly if statement. Break it up into sub-functions like I suggested.

[Mike Garber]

I figured it out guys, thanks