1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

How to capture wrong inputs using atoi??

Discussion in 'C' started by askmewhy25, Mar 1, 2010.

  1. askmewhy25

    askmewhy25 New Member

    Joined:
    Jan 24, 2010
    Messages:
    49
    Likes Received:
    0
    Trophy Points:
    0
    My program can already capture strings or characters but the problem is that in some parts of the program it does not prompt that his/her input is already invalid..how can i solve this help please..

    Example of problem
    Code:
    ......
    ......
    do{
          system("cls");
          printf("Polynomial Evaluation\n\n");
          printf("Enter the Order of Polynomial (max. 10): ");
          scanf("%s",&error);
          n=atoi(error);
                                               
        double poly[n+1];
        //Enter values of the constants
        for(m=n;m>=0;m--){
          printf("Please enter the constant for X raised to the %dth: ", m);
          scanf("%s",&error);
          poly[m]=atof(error);
          }
        printf("Enter the value of X: ");
        scanf("%s",&error);
        x=atof(error);
        
        if(n>10||n<1){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
        if(m>10000||m<-10000){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
        if(x>10000||x<-10000){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
          }while(n>10||n<1||m>10000||m<-10000||x>10000||x<-10000);
    ......
    ......
    

    This is my full program
    Code:
    //This program can evaluate a 10th order linear polynomial equation. This 
    //program can also solve for statistical algorithms such as mean, summation and
    //standard deviation of up to 10 maximum data and solve for matrix operations
    //of 3 by 3 matrices such as addition, multiplication and transpose of matrix.
    
    #include <stdio.h>
    #include <conio.h>
    #include <math.h>
    #include <stdlib.h>
    #include <string.h>
    
    //Prototypes for Polynomial Evaluation
    double Polynomial();
    
    //Prototypes for Statistical Algorithms
    double Mean();
    double Standard();
    double Summation();
    
    //Prototypes for Matrix Operations
    double Add();
    double Multi();
    double Trans();
    
    //Start Program
    main(){
           int selection;
           char error[128];
           //Variables for Polynomial Evaluation
           double polysum=0, x;
           int n, QA, m;
           //Variables for Statistical Algorithms
           int SA,a,b,sum=0,data[10];
           float mean;
           double calc,sd;       
           //Variables for Matrix Operation
           int MO,i,k,j,c1,c2,r1,r2;
           int m1[3][3],m2[3][3],m3[3][3];
           //Menu Selection Screen    
           do{
             system("cls");
             printf("Menu Selection Screen\n\n");
             printf("1 - Polynomial Evaluation\n");
             printf("2 - Statistical Algorithms\n");
             printf("3 - Matrix Operation\n");
             printf("4 - Exit\n");
             
             scanf("%s",&error);
             selection=atoi(error);
             switch(selection){
               case 1://This evaluates the polynomial
                 Polynomial();
                 break;
               case 2:
                 do{
                   sum=0;
                   mean=0;
                   calc=0;
                   sd=0;
                   system("cls");
                   printf("Statistical Algorithms\n\n");
                   printf("1 - Mean\n");
                   printf("2 - Standard Deviation\n");
                   printf("3 - Summation of data\n");
                   printf("4 - Go Back to Menu Selection Screen\n");
                                                                       
                   scanf("%s",&error);
                   SA=atoi(error);
                   switch(SA){
                     case 1:
                       Mean();
                       break;
                     case 2:
                       Standard();
                       break;
                     case 3:
                       Summation();
                       break;
                     case 4://Return to the selection screen
                       main();
                       break;
                     default://The program redirects invalid inputs to this part
                       system("cls");
                       printf("Invalid Input. Please try again!!!\n");
                       printf("Please press the spacebar to continue!!");
                       getche();
                       break;
                     }
                   }while(SA!=4); 
                 break;
               case 3:
                 do{
                   system("cls");
                   printf("Matrix Operation\n\n");
                   printf("1 - Matrix Addition\n");
                   printf("2 - Matrix Multiplication\n");
                   printf("3 - Transpose of Matrix\n");
                   printf("4 - Go Back to Menu Selection Screen\n");
                   
                   scanf("%s",&error);
                   MO=atoi(error);
                   switch(MO){
                     case 1:
                       Add();
                       break;
                     case 2:
                       Multi();
                       break;
                     case 3:
                       Trans();
                       break;
                     case 4:
                       main();
                       break;
                     default://The program redirects invalid inputs to this part
                       system("cls");
                       printf("Invalid Input. Please try again!!!\n");
                       printf("Please press the spacebar to continue!!");
                       getche();
                       break;
                     }
                    getche();
                    }while(MO!=4);                
                 break;
               case 4://Exit
                 return 0;
                 break;
               default://The program redirects invalid inputs to this part
                 system("cls");
                 printf("Invalid input. Please try again!!!\n");
                 printf("Please press the spacebar to continue!!");
                 getche();
                 break;
               }
             }while(selection>4 || selection<=0);
    }
    
    //Polynomial Function
    double Polynomial(){
      //Variables for Polynomial Evaluation
      double polysum=0, x;
      int n, QA, m;
      char error[128];
      
      do{
        do{
          system("cls");
          printf("Polynomial Evaluation\n\n");
          printf("Enter the Order of Polynomial (max. 10): ");
          scanf("%s",&error);
          n=atoi(error);
                                               
        double poly[n+1];
        //Enter values of the constants
        for(m=n;m>=0;m--){
          printf("Please enter the constant for X raised to the %dth: ", m);
          scanf("%s",&error);
          poly[m]=atof(error);
          }
        printf("Enter the value of X: ");
        scanf("%s",&error);
        x=atof(error);
        
        if(n>10||n<1){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
        if(m>10000||m<-10000){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
        if(x>10000||x<-10000){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
          }while(n>10||n<1||m>10000||m<-10000||x>10000||x<-10000);
        
        double poly[n+1];
        for(m=n;m>=0;m--)
          polysum+=poly[m]*pow(x,m);
        printf("The evaluated value of the %dth Order Polynomial  %.2lf\n", n, polysum);//Print answer
        printf("Please press the spacebar to continue!!\n");
        getche();
        do{//This used to ask the user if s/he wants to repeat the evaluation
          system("cls");
          printf("Do you want to repeat the computation?\n\n");
          printf("1 - Yes\n");
          printf("2 - No\n");
          scanf("%s",&error);
          QA=atoi(error);
          switch(QA){
            case 1:
              break;
            case 2://Return to the selection screen
              main();
              break;
            default://The program redirects invalid inputs to this part
              system("cls");
              printf("Invalid input. Please try again!!!\n");
              printf("Please press the spacebar to continue!!");
              getche();
              break;   
              }
          }while(QA>2||QA<1);
          polysum=0;
        }while(QA==1);     
    }
    
    //Mean Function
    double Mean(){
      int SA,a,b,sum=0,data[10];
      float mean;
      double calc,sd;
      char error[128];
      
      do{//This solves for the Mean
        system("cls");
        printf("Mean\n\n");
        printf("Enter the Number of Data (max. 10): ");
        scanf("%s",&error);
        b=atoi(error);
        if(b>10||b<1){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
        }while(b>10||b<1);
      for(a=0;a<b;a++){//Enter values of the data
        printf("Enter the Actual Values of Data %d: ", a+1);
        scanf("%s",&error);
        data[a]=atoi(error);
        }
      for(a=0;a<b;a++){
        sum=sum+data[a];
        }
      mean=(float)sum/a;
      printf("The Mean of the Data is %f\n",mean);//Print answer
      printf("Please press the spacebar to continue!!");
      getche();
    }
    
    //Standard Deviation Function
    double Standard(){
      int SA,a,b,sum=0,data[10];
      float mean;
      double calc,sd;
      char error[128];
      
      do{
        system("cls");
        printf("Standard Deviation\n\n");
        printf("Enter the Number of Data (max. 10): ");
        scanf("%s",&error);
        b=atoi(error);
        if(b>10||b==0){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!\n");
          getche();
          }
        }while(b>10||b==0);
      for(a=0;a<b;a++){
        printf("Enter the Actual Values of Data %d: ", a+1);
        scanf("%s",&error);
        data[a]=atoi(error);
        }
      if(b==1){
        printf("The Standard Deviation the Data is 0\n");
        printf("Please press the spacebar to continue!!");
        getche();
        }
      else{
        for(a=0;a<b;a++){
          sum=sum+data[a];
          }
        mean=(float)sum/a;
        for(a=0;a<b;a++){
          calc+=pow((data[a]-mean),2);
          }
        sd=sqrt(calc/(b-1));
        printf("The Standard Deviation the Data is %lf\n",sd);
        printf("Please press the spacebar to continue!!");
        getche();
      }
    }
    
    //Summation Function
    double Summation(){
      int SA,a,b,sum=0,data[10];
      float mean;
      double calc,sd;
      char error[128];
      
      do{//This solves for the Summation
        system("cls");
        printf("Summation of Data\n\n");
        printf("Enter the Number of Data (max. 10): ");
        scanf("%s",&error);
        b=atoi(error);
        if(b>10||b<1){
          system("cls");
          printf("Invalid input. Please try again!!!\n");
          printf("Please press the spacebar to continue!!");
          getche();
          }
        }while(b>10||b<1);
      for(a=0;a<b;a++){//Enter values of the data
        printf("Enter the Actual Values of Data %d: ", a+1);
        scanf("%s",&error);
        data[a]=atoi(error);
        }
      for(a=0;a<b;a++){
        sum=sum+data[a];
        }
      mean=(float)sum/a;
      printf("The Summation of the Data is %d\n",sum);//Print answer
      printf("Please press the spacebar to continue!!");
      getche();  
    }
    
    //Matrix Operation Functions
    //Martices Addition Function
    double Add(){
      int MO,i,k,j,c1,c2,r1,r2;
      int m1[3][3],m2[3][3],m3[3][3];
      char error[128];
      
      system("cls");
      printf("Enter the number of rows of the first matrix (max 3): ");
      scanf("%s",&error);
      r1=atoi(error);
      printf("Enter the number of columns of the first matrix (max 3): ");
      scanf("%s",&error);
      c1=atoi(error);
      printf("Enter the number of rows of the second matrix (max 3): ");
      scanf("%s",&error);
      r2=atoi(error);
      printf("Enter the number of columns of the second matrix (max 3): ");
      scanf("%s",&error);
      c2=atoi(error);
      if((r1==r2)&&(c1==c2)){
        printf("Addition is possible:\n");
        printf("Input Matrix one:\n");
        for(i=0;i<r1;i++){
          for(j=0;j<c1;j++){
            printf("Enter an element (row:%d column: %d): ",i+1,j+1);
            scanf("%s",&error);
            m1[i][j]=atoi(error);
            }
          }
        printf("You have entered the First Matrix as follows:\n");
        for(i=0;i<r1;i++){
          for(j=0;j<c1;j++)
            printf("%d\t",m1[i][j]);
            printf("\n");
          }
        printf("Input Matrix two:\n");
        for(i=0;i<r2;i++){
          for(j=0;j<c2;j++){
            printf("Enter an element (row:%d column: %d): ",i+1,j+1);
            scanf("%s",&error);
            m2[i][j]=atoi(error);
            }
          }
        printf("You have entered the Second Matrix as follows:\n");
        for(i=0;i<r2;i++){
           for(j=0;j<c2;j++)
           printf("%d\t",m2[i][j]);
           printf("\n");
          }
        /* Addition of Matrix*/
        for(i=0;i<r1;i++){
          for(j=0;j<c1;j++)
            m3[i][j]=m1[i][j]+ m2[i][j];
          }
        printf("The sum is:\n");
        for(i=0;i<c1;i++){
          for(j=0;j<r1;j++)
            printf("%5d",m3[i][j]);
            printf("\n");
          }
      }
      else
        printf("\n Addition is not possible:-");
      }
    
    //Matrices Multiplication Function
    double Multi(){
      int MO,i,k,j,c1,c2,r1,r2;
      int m1[3][3],m2[3][3],m3[3][3];
      char error[128];
      
      system("cls");
      printf("Enter the number of rows of the first matrix (max 3): ");
      scanf("%s",&error);
      r1=atoi(error);
      printf("Enter the number of columns of the first matrix (max 3): ");
      scanf("%s",&error);
      c1=atoi(error);
      printf("Enter the number of rows of the second matrix (max 3): ");
      scanf("%s",&error);
      r2=atoi(error);
      printf("Enter the number of columns of the second matrix (max 3): ");
      scanf("%s",&error);
      c2=atoi(error);
      if(c1==r2){
        printf("Multiplication is possible:\n");
        printf("Input value of Matrix one:\n");
        for(i=0;i<r1;i++){
          for(j=0;j<c1;j++){
            printf("Enter an element (row:%d column: %d): ",i+1,j+1);
            scanf("%s",&error);
            m1[i][j]=atoi(error);
            }
          }
        printf("You have entered the First Matrix as follows:\n");
        for(i=0;i<r1;i++){
          for(j=0;j<c1;j++)
            printf("%d\t",m1[i][j]);
            printf("\n");
          }
        printf("Input value of Matrix two:\n");
        for(i=0;i<r2;i++){
          for(j=0;j<c2;j++){
            printf("Enter an element (row:%d column: %d): ",i+1,j+1);
            scanf("%s",&error);
            m2[i][j]=atoi(error);
            }
          }
        printf("You have entered the Second Matrix as follows:\n");
        for(i=0;i<r2;i++){
          for(j=0;j<c2;j++)
            printf("%d\t",m2[i][j]);
            printf("\n");
          }
        for(i=0;i<r1;i++)
          for(j=0;j<c2;j++){
            m3[i][j]=0;
            for(k=0;k<c1;k++)
              m3[i][j]=m3[i][j]+m1[i][k]*m2[k][j];
            }
        /*Displaying final matrix*/
        printf("Multiplication of Matrix:\n");
        for(i=0;i<r1;i++){
          for(j=0;j<c2;j++)
            printf("\t%d",m3[i][j]);
            printf("\n");
          }
        }
      else
        printf("Multiplication is not possible");
    }
    
    //Matrix Transpose Function
    double Trans(){
      int MO,i,k,j,c1,c2,r1,r2;
      int m1[3][3],m2[3][3],m3[3][3];
      char error[128];
      
      system("cls");
      printf("Enter the number of row: ");
      scanf("%s",&error);
      r1=atoi(error);
      printf("Enter the number of coloum: ");
      scanf("%s",&error);
      c1=atoi(error);
      printf("Enter the element\n\n");
      for(i=0;i<r1;i++){
        for(j=0;j<c1;j++){
          printf("Enter an element (row:%d column: %d): ",i+1,j+1);
          scanf("%s",&error);
          m1[i][j]=atoi(error);
          m2[j][i]=m1[i][j];
          }
        }
      /*Displaying transpose of matrix*/
      printf("Transpose of Matrix is:\n");
      for(i=0;i<r1;i++){
        for(j=0;j<c1;j++)
          printf("\t%d",m2[i][j]);
          printf("\n");
        }
    }
    
    
    
     
  2. Gene Poole

    Gene Poole New Member

    Joined:
    Nov 10, 2009
    Messages:
    93
    Likes Received:
    5
    Trophy Points:
    0
    instead of atoi()/atof() try strtol()/strtod(). They take an additional parameter that tells where the conversion stops. With that info, you can determine if the input is valid.

    Here's a demo:
    Code:
    #include <stdlib.h>
    #include <string.h>
    
    int main()
    {
      char test1[]="1.0225";
      char test2[]="1.0225 with junk";
      char test3[]="All junk";
      
      double d;
      char *p;
      int len;
    
      len=strlen(test1);
      d=strtod(test1,&p);
      if(p==test1){
        printf("No conversion tool place. Garbage: %s\n",p);
      }else if((p-test1)<len){
        printf("partial converions took place.  Value: %lf, garbage: %s\n",d,p);
      }else{
        printf("Complete conversion took place: %lf\n",d);
      }
    
      len=strlen(test2);
      d=strtod(test2,&p);
      if(p==test2){
        printf("No conversion tool place. Garbage: %s\n",p);
      }else if((p-test2)<len){
        printf("partial converions took place.  Value: %lf, garbage: %s\n",d,p);
      }else{
        printf("Complete conversion took place: %lf\n",d);
      }
    
      len=strlen(test3);
      d=strtod(test3,&p);
      if(p==test3){
        printf("No conversion tool place. Garbage: %s\n",p);
      }else if((p-test3)<len){
        printf("partial converions took place.  Value: %lf, garbage: %s\n",d,p);
      }else{
        printf("Complete conversion took place: %lf\n",d);
      }
    
    
      return 0;
    }
    
     
  3. askmewhy25

    askmewhy25 New Member

    Joined:
    Jan 24, 2010
    Messages:
    49
    Likes Received:
    0
    Trophy Points:
    0
    Sir I understand what your demo want to say but what should be the values of the tests array if there would be no range of values to be inputted and the only thing that the program should capture if the input is a character or a string
     
  4. Gene Poole

    Gene Poole New Member

    Joined:
    Nov 10, 2009
    Messages:
    93
    Likes Received:
    5
    Trophy Points:
    0
    strtol and strtod will take any amount of leading whitespace up to the number. It will then try to convert the number using a simple set of rules which allow leading zeros, +/-, and with wcstod, will accept ieee exponential notation (like "3.04e-12"). At the first sign of something NOT able to be converted (like the "1.0225 with junk" after the '5'), it stops converting and sets the second argument to the place where it stopped. This can then be used (as I show in the demo) to determine if the number completely converted, partially converted, or didn't convert at all. You can use the logic as above to re-prompt or warn the user, etc.
     

Share This Page