Thread: Functions and Character Arrays HELP!

  1. #1
    Registered User
    Join Date
    Jul 2012

    Functions and Character Arrays HELP!

    #include <stdio.h>
    #include <string.h>
    //char Rule1(int);
    int Rule2(char);
    void Display();
    char input_string[100];
    int main()
    	printf("Please Enter String: ");
    	scanf("%s", &input_string);
    	char input_string[100];
    int Rule2(char* input_string) // Rule 2 function
    	char AY[2]={'A','Y'};
    		if(input_string[0] == 'A' || input_string[0] == 'a' || input_string[0] == 'E' || input_string[0] == 'e' || input_string[0] == 'I' || input_string[0] == 'i' || input_string[0] == 'O' || input_string[0] == 'o' || input_string[0] == 'U' || input_string[0] == 'u') 
    				strcat(input_string, AY);
    				Display(); // Displays new word
    void Display()
    	printf("The word you enter is %s\n", input_string);
    	//PigLatin=fopen("piglatin.txt", "w");
    		//fprintf(PigLatin, "%s", input_string);
    i get an C2143 error at the Rule2 function call in main and its driving me crazy! Please help! thanks

  2. #2
    Frequently Quite Prolix dwks's Avatar
    Join Date
    Apr 2005
    That's because the prototype for Rule2 is Rule2(char), while its definition is Rule2(char*). Notice the extra '*'. These things have to match.

    A few other issues: You declare input_string as a global variable, and then you declare another variable with the same name inside main() which hides the global one. You'll definitely end up using one variable instead of the other by accident and wondering why there's no data in the array.

    You should be declaring input_string inside main() before you use it (i.e. before the scanf call). Then passing it to Rule2 is fine (although you need to change the prototype to be char* instead of char as I mentioned). There's a handy function called tolower() [and also toupper()] in <ctype.h> that will turn 'A' into 'a', which you may want to use.

    Also: your string AY is not null-terminated, so the strcat() will do a buffer overrun and may crash your program. Definitely declare it as
    char AY[3] = {'A','Y','\0'};
    char AY[3] = "AY";  // implicit \0
    char AY[] = "AY";  // implicit size plus implicit \0
    All those are equivalent, the last obviously being the simplest. However, you don't even need a variable if you're just strcat'ing, you can say
    strcat(input_string, "AY");
    Hmm... also, main should return 0. You should turn on compiler warnings, I'm sure they'll help you spot some mistakes before they get too buried. For g++/gcc just add "-Wall -Wextra" to your command line.

    Sorry if that was a bit harsh/rushed... wasn't intended to be. You've actually posted some code which is more than some people do. Please feel free to ask if you have questions.

    [edit] P.S. If you're feeling adventurous, switch statements or strchr() [a function in string.h] can be used to check if one character belongs to a set of characters you're interested in (e.g. vowels). Combine with tolower() for best effect. [/edit]
    Last edited by dwks; 07-17-2012 at 01:44 PM.

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  3. #3
    Registered User hk_mp5kpdw's Avatar
    Join Date
    Jan 2002
    Northern Virginia/Washington DC Metropolitan Area
    This too:
    printf("Please Enter String: ");
    scanf("%s", &input_string);
    In this context, the & is not needed. The array name by itself is sufficient and is treated as a char pointer so you don't need the address-of operator to turn it into one.
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
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  4. #4
    Registered User
    Join Date
    Jul 2012
    Thanks for the help guys! This bit of code was copy and pasted from my project which was open on another window of visual studio so things like the return 0 i miss :P

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