pattern checking in a string question..

This function needs to check if the sting is a polynomial .
It check it for some sort pattern. If this string is not builded by this pattern then it return
0. else it returns 1

i translated this function from java

can you tell me what pattern it checks in this string??
(variable length is the length of the string)

Code:

---


int checkPoly(char[] str,int length)
        {
          int result;
          result=false;
          int index;
          int index2;
            int index3;


 

          for( index=0;((index<length)&& (((str[length-1]>'0')&&(str[length-1]<'9')))));index++)
          {
                  if((str[index]=='(')&&(str[index+1]!='('))
                  {
                       
                          for (index2=0;index2<length;index2++)
                          {
                                  if(str[index2]==')')
                                  {                                       
                                          if((str[index2+1]=='x')&&(str[index2+2]=='^')&&((str[index2+3]>'0')&&(str[index2+3]<'9'))))

                                          {
                                                  result=1;
                                                  index=length;
                                                  for (index3=index2+2;((index3<length)&&(((length)-(index3+2)!=0)));index3++)
                                                  {                                                       
                                                          if(str[index3]=='(')
                                                          {
                                                                  if(str[index3-1]=='+')
                                                                  {                                                                         
                                                                          index3=length;
                                                                          result=1;
                                                                  }
                                                                  else
                                                                  {
                                                                          index3=length;
                                                                          index2=length;                               
                                                                          result=0;
                                                                  }
                                                                 
                                                          }else{}
                                                  }
                                          }else
                                          {
                                                  result=0;
                                                  index2=length;
                                                  index=length;
                                                 
                                          }
                                  }else{}
                          }
                  }else {
                          result=0;
                          index=length;
                          }
               
      }
          return result;
        }

---

Quote:

---

Originally Posted by transgalactic2

This function needs to check if the sting is a polynomial .
It check it for some sort pattern. If this string is not builded by this pattern then it return
0. else it returns 1

i translated this function from java

can you tell me what pattern it checks in this string??
(variable length is the length of the string)

---

You did not quite finish your translation. There is some stuff in there that is not C code. And which string are you referring to here?

Quote:

---

Originally Posted by transgalactic2

i translated this function from java

---

You need to be aware of differences in syntax, e.g., the syntax for array declaration.

Quote:

---

Originally Posted by transgalactic2

can you tell me what pattern it checks in this string??
(variable length is the length of the string)

---

You need to make some effort on your part first, e.g., tell us what you think the function does and the reasoning behind your answer.

One way to help you test your answer is to actually run the program with sample input, and to do that your program must at least be syntactically correct (or you compile and run the Java version of the program). It would also help if you indented your code properly and reduced the number of superfluous parentheses, e.g.,

Code:

---

int checkPoly(char str[], int length)
{
    int result = 0;
    int index;
    int index2;
    int index3;

    for (index = 0;
        (index < length) && (str[length - 1] > '0') && (str[length - 1] < '9');
        index++)
    {
        if ((str[index] == '(') && (str[index + 1] != '('))
        {
            for (index2 = 0; index2 < length; index2++)
            {
                if (str[index2] == ')')
                {
                    if ((str[index2 + 1] == 'x') && (str[index2 + 2] == '^')
                        && (str[index2 + 3] > '0') && (str[index2 + 3] < '9'))
                    {
                        result = 1;
                        index = length;
                        for (index3 = index2 + 2;
                            (index3 < length) && ((length - (index3 + 2)) != 0);
                            index3++)
                        {
                            if (str[index3] == '(')
                            {
                                if (str[index3 - 1] == '+')
                                {
                                    index3 = length;
                                    result = 1;
                                }
                                else
                                {
                                    index3 = length;
                                    index2 = length;
                                    result = 0;
                                }
                            }
                        }
                    }
                    else
                    {
                        result = 0;
                        index2 = length;
                        index = length;
                    }
                }
            }
        }
        else
        {
            result = 0;
            index = length;
        }
    }
    return result;
}

---

(Note that I removed the empty else blocks, but left some superfluous parentheses in even though I would normally remove them.)

where did leave java syntax?

Quote:

---

Originally Posted by transgalactic2

where did leave java syntax?

---

I have already given you a hint: array declaration syntax. You should have tried to compile and run your code before posting it on a forum.

Code:

---

int checkPoly(char[] str,int length)
        {
          int result;
          result=false;

---

so i need to change char str[] >> char[] str

i can see its something like:
(num*x^num + ..) +

but i am not sure
i cant check this thing on a compiler
because its a pattern
it doesnt give a hint like "you are close but you should fix the col"
it gives true or false

In C99 with <stdbool.h> included the use of false and mixing declarations and code is allowed.

I meant 0 and 1.
my point is i could test ten inputs and i coudnt see i one input is closer to the pattern then the
other ones.

I can see its something like:
(numx^num + ..) +

But i am not sure.

Quote:

---

Originally Posted by laserlight

In C99 with <stdbool.h> included the use of false and mixing declarations and code is allowed.

---

That is true, however I was assuming (perhaps incorrectly) that the OP had not made a conscious decision to leave that in, but rather was an oversight.

Quote:

---

Originally Posted by transgalactic2

i cant check this thing on a compiler
because its a pattern
it doesnt give a hint like "you are close but you should fix the col"
it gives true or false

---

Well, you already know that the function is supposed to return 1 if the string matches some polynomial expression syntax and 0 otherwise. From what I understand, what you want to do is to precisely determine what is this pattern that the function checks for. This means carefully looking over the function's implementation.

When you have come to a conclusion, you can then test if you are wrong by running the program with carefully selected input and checking if the output is what you expect. If the output is unexpected then you know that your conclusion must be wrong, otherwise you have more evidence that your conclusion is correct (but unless you exhaustively test all possible input you cannot be absolutely certain that your conclusion is correct merely by testing).

i am trying to run this function

and on this line i was told that
|12|warning: char format, different type arg (arg 2)|

Code:

---

scanf("%c",&str[index]);

---

and another warning says
|16|warning: implicit declaration of function `checkPoly'|

whats what do i need to change?

Quote:

---

Originally Posted by transgalactic2

i am trying to run this function

and on this line i was told that
|12|warning: char format, different type arg (arg 2)|

Code:

---

scanf("%c",&str[index]);

---

and another warning says
|16|warning: implicit declaration of function `checkPoly'|

whats what do i need to change?

---

For the first warning, you are asking scanf to get a char, but obstensibly passing it an address to an int array.

For the second warning, you are trying to call the function from main without a function prototype.

Code:

---

int checkPoly(char str[], int length);
...
int main(void)
{
....
}

---

You could also just make sure the function code comes after the main function in the same source file.

in the end i need it to be a "string" (char array)

what is the problem??

Quote:

---

Originally Posted by transgalactic2

in the end i need it to be a "string" (char array)

---

Use fgets() instead. I have an example in the thread printing from output...

in my previous problem i did exactly the same thing for inputting numbers into a 2d array .
why its not letting me input chars in a row?

Code:

---


int main() {
    int index;
    int str[40];
    int i;
    int length;

 printf("enter length\n");
 scanf("%d",&length);
 printf("enter string\n");
 for(index;index<length;index++){
  scanf("%c",&str[index]);
 }
 i=getchar();

---

Quote:

---

Originally Posted by transgalactic2

in my previous problem i did exactly the same thing for inputting numbers into a 2d array .
why its not letting me input chars in a row?

---

Note that your array is an array of ints, not chars. If you really want to read char by char in a loop, then it probably makes more sense to just call getchar() instead of using scanf().

i want to enter my string
from a row of chars which i enter myself

in every way possible

i tried

Code:

---

int main() {
    int index;
    int str[40];
    int i;
    int length;

 printf("enter length\n");
 scanf("%d",&length);
 printf("enter string\n");

  scanf("%c",&str); //13



 printf("%d",checkPoly(str,length));
 return 0;
}

---

For starters, change this:

Code:

---

int str[40];

---

to:

Code:

---

char str[40];

---

After that your earlier code would probably work, just that it is a little weird to use scanf() in a loop to read character by character.

i did that.
it doesnt let me enter the string in a row
it doesnt even let me type anthing
i dont mind changing the method

i want it to let me enter the string by a row

Code:

---

#include <stdio.h>
int checkPoly(char str[], int length);

int main() {
    int index;
    char str[40];
    int i;
    int length;

 printf("enter length\n");
 scanf("%d",&length);
 printf("enter string\n");
 for(index;index<length;index++){
  scanf("%c",&str[index]);
 }
 i=getchar();

---

You never initialise 'index' to any value before you actually use it.

There is another potential problem in that the user would have to input enough characters to fill the entire string, and you do not account for the null terminator.

ok i looked up in the javadoc of the file and it should
recognize "(1.0+1.0i)x^1 +(1.0+1.0i)x^0"

but i cant see that in the code
there is no mention for "i' char in the code

??

and it doesnt work it doesnt say 1 on that example

i cant understand how its being built.

what each part is suppossed to do in order to check for a pattern

this program is an example to a pattern checking program

i want to check other patterns in the string

how to pattern checking proccess works?

Quote:

---

Originally Posted by transgalactic2

and it doesnt work it doesnt say 1 on that example

---

Cross reference with the Java version: does the Java program return the correct answer? If it does, then perhaps you converted the program wrongly. If not, then clearly there is a bug in the program (or maybe the documentation, or both).

in general is this the way
i need to do pattern checking?

or there is an easier way

Quote:

---

Originally Posted by transgalactic2

in general is this the way
i need to do pattern checking?

---

That depends on what you mean by "the way". Certainly checking if input follows some format means parsing the input.

the way i meant "complex loop" system

Quote:

---

Originally Posted by transgalactic2

the way i meant "complex loop" system

---

Yes, though there would be the use of functions to hide the complexity, and with say, a recursive descent parser you would likely use recursion instead of iteration.

i got only this "working code"

is there other codes to rely on?

Quote:

---

Originally Posted by transgalactic2

i got only this "working code"

is there other codes to rely on?

---

You mean "can I copy some other code" - I'm sure you can. The example of a recursive descent parser should be searchable.

But I think, judging from your questions, that you need to study more of the basics of programming and (more importanly perhaps) troubleshooting - both compiler errors and logical errors. This is a HUGE part of programming to understand what the code does, and figure out why it doesn't work - and you can't go through the rest of your life asking on forums.

--
Mats