I am comfortable with Java Programming but C... I need help

This is a discussion on I am comfortable with Java Programming but C... I need help within the C Programming forums, part of the General Programming Boards category; Well I am stumped. Must be scanf but tried fgets and no dice. See what you can do with this. ...

  1. #1
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    I am comfortable with Java Programming but C... I need help

    Well I am stumped. Must be scanf but tried fgets and no dice.

    See what you can do with this.

    The program runs nicely through until ready to do it again and then the program loops forever.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    
    int
    main(void){
    	int decision = 121, guessedNum;
    	while(decision == 121){
    		srand( time(NULL));
    		int target = rand() % 100 + 1, count = 0;
    		while (guessedNum != target){
    			printf("Guess a number between 1 and 100: ");
    			scanf("%d", &guessedNum);
    			fflush(stdin);
    			if (guessedNum > target){
    				printf("The number is lower. Try again.\n");
    				count += 1;
    			}
    			else if(guessedNum < target){
    				printf("The number is higher. Try again.\n");
    				count += 1;
    			}
    			else
    			{
    				printf("You guessed correctly!\n");
    				printf("It took you %d tries.\n", count);
    			}
    		}
    		printf("Would you like to play again? y(es) or n(o) :");
    		scanf("%d", &decision);
    	}
    
    	return 0;
    }

  2. #2
    Registered User Swarvy's Avatar
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    What exactly are you typing when it asks you to play again? Are you typing a 'y' or 'Y', because, if so, that is your problem. Your code asks for a number and if that number is 121 then it will loop around again.

    So, when it gets to this line of code:
    Code:
    printf("Would you like to play again? y(es) or n(o) :");
    Try typing '121' and seeing what happens. Does it loop properly?

  3. #3
    C++ Witch laserlight's Avatar
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    You are trying to read decision as an int with scanf, but you expect 'y' or 'n' as input. That does not make sense. Use getchar() instead of scanf, and then compare with 'y', not the magic number 121.
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  4. #4
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    Well my frustration has come to an end. Oddly enough I never thought to use getchar and the endless looping has stooped. Thank you for the suggestions.

  5. #5
    and the hat of int overfl Salem's Avatar
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    > fflush(stdin);
    Ewww - unclean!

    There's a FAQ - time to read it.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  6. #6
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    Well I am still unsure as to how to get one character typed at the kb into my program for comparison to a simple while loop.

    Using getchar does not work or scanf or anything else.

  7. #7
    C++ Witch laserlight's Avatar
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    What is your current code?
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  8. #8
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    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    
    int
    main(void){
    	int decision = 'y', guessedNum;
    	while(decision == 'y'){
    		srand( time(NULL));
    		int target = rand() % 100 + 1, count = 0;
    		while (guessedNum != target){
    			printf("Guess a number between 1 and 100: ");
    			scanf("%d", &guessedNum);
    			fflush(stdin);
    			if (guessedNum > target){
    				printf("The number is lower. Try again.\n");
    				count += 1;
    			}
    			else if(guessedNum < target){
    				printf("The number is higher. Try again.\n");
    				count += 1;
    			}
    			else
    			{
    				printf("You guessed correctly!\n");
    				printf("It took you %d tries.\n", count);
    			}
    		}
    		printf("Would you like to play again? y(es) or n(o): ");
    		decision = fgetc(stdin);
    	}
    
    	return 0;
    }

  9. #9
    C++ Witch laserlight's Avatar
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    It works for me, though I would change:
    Code:
    fflush(stdin);
    to:
    Code:
    getchar();
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  10. #10
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    If I remove fflush(stdin) and use decision = getchar() no matter what I do the program ends after a successful guess.

    What give with this language. How is that getchar() doesn't even stop to actually get a char from stdin??

  11. #11
    Registered User Swarvy's Avatar
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    Not:
    Code:
    decision = getchar();
    Just:
    Code:
    getchar();
    Don't assign decision to the output of that function.

  12. #12
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    But whole point is to choose if you wish to run the program again or not. I tested getchar in another project independently and it performs as intended. Why it does not in Eclipse on a MacBook Pro is beyond my understanding. The program should stop and get input ad that it is not doing so makes no sense.

  13. #13
    Registered User Swarvy's Avatar
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    You only call the function 'fflush' once during your program and it isn't at the end of the while loop when you are testing to see if the user wants to replay.
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    
    int main(void){
    	int decision = 'y', guessedNum;
    	while(decision == 'y'){
    		srand( time(NULL));
    		int target = rand() % 100 + 1, count = 0;
    		while (guessedNum != target){
    			printf("Guess a number between 1 and 100: ");
    			scanf("%d", &guessedNum);
    			fflush(stdin);
    			if (guessedNum > target){
    				printf("The number is lower. Try again.\n");
    				count += 1;
    			}
    			else if(guessedNum < target){
    				printf("The number is higher. Try again.\n");
    				count += 1;
    			}
    			else
    			{
    				printf("You guessed correctly!\n");
    				printf("It took you %d tries.\n", count);
    			}
    		}
    		printf("Would you like to play again? y(es) or n(o): ");
    		decision = fgetc(stdin);
    	}
    	
    	return 0;
    }
    Change that fflush to:
    Code:
    getchar();
    Everything else is fine.

  14. #14
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    I fixed it and it works perfectly now.
    decision - getchar()
    decision = getchar()

    The first line eats a new line after the successful entry of the correct guess. The second line actually prompts for and gets the character from stdin.

    Library for stdio is crap in this crappy language and only thing worth anything is fgets but if the stupid buffer wont flush itself or reset or return to 0 and holds onto new lines and EOF then crap.

  15. #15
    Registered User Swarvy's Avatar
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    Trust me on this one, C isn't a crappy language it is just very unforgiving - you have to be very precise with your code. Java allows a little more flexibility because it is run through a virtual machine.

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