Problem with function!

Hello to all, newbie here.

I need help with my function. Here is the code for the function:

Code:

---

char content_scan( char sequence)
    {
        int x ;
       
        for(x=0 ; x < (strlen(sequence)) ; x++)
            {
                while( sequence[x] )
                    {
                        if( sequence[x] == 'U' )
                            {
                                return "RNA" ;
                                break ;
                            }
                        else if (sequence[x] == 'A' || x == 'C' || x == 'G' || x == 'T')
                            {
                                return "DNA" ;
                                break ;
                            }
                        else
                            {
                                return "PROTEIN" ;
                                continue ;
                            }
                    }
            }
    }

---

I am trying to return the output to the variable "loadedSequences[nSequences].type" which is a character array with the following statement:

Code:

---

loadedSequences[nSequences].type = content_scan(loadedSequences[nSequences].data) ;

---

The argument for the function will be a long string of letters.

Any help would be great.

First off, your function definition says it returns a single character:

Code:

---

char content_scan( char sequence)

---

After you fix that, I'm not sure if there will be a scope issue with your returned strings or not once the function has exited (since you'll be passing back a pointer to the string and not the string itself). Try it out.

Todd

Code:

---

char content_scan( char sequence)

---

Quote:

---

The argument for the function will be a long string of letters.

---

Not the way you've coded it, it won't!!

Surely you are getting compile errors. And since you are, please post them so we don't have to play hide-and-seek or peek-a-boo analyzing your code.

Todd

Still receiving errors. Here are the errors:

beta_seqTool.c: In function ‘content_scan’:
beta_seqTool.c:14: warning: passing argument 1 of ‘strlen’ makes pointer from integer without a cast
beta_seqTool.c:16: error: subscripted value is neither array nor pointer
beta_seqTool.c:18: error: subscripted value is neither array nor pointer
beta_seqTool.c:23: error: subscripted value is neither array nor pointer
beta_seqTool.c: In function ‘main’:
beta_seqTool.c:128: warning: passing argument 1 of ‘content_scan’ makes integer from pointer without a cast

Code:

---

int content_scan( char sequence)
    {
        int x ;
       
14        for(x = 0 ; x < strlen(sequence) ; x++)
            {
16                while( sequence[x] )
                    {
18                        if( sequence[x] == 'U' )
                            {
                                return 1 ; // RNA
                                break ;
                            }
23                        else if (sequence[x] == 'A' || x == 'C' || x == 'G' || x == 'T')
                            {
                                return 2 ; // DNA
                                break ;
                            }
                        else
                            {
                                return 3 ; // PROTEIN
                                continue ;
                            }
                    }
            }
    }

---

Code:

---

128    loadedSequences[nSequences].type = content_scan(loadedSequences[nSequences].data) ;

---

Also, is there a way I can return a string (i.e DNA, RNA, or PROTEIN as my value for loadedSequences[nSequences].type?

Code:

---

strlen(sequence)

---

You can't do a strlen() on a single character.

Code:

---

sequence[x]

---

You can't subscript a single character.

Todd

Quote:

---

Also, is there a way I can return a string (i.e DNA, RNA, or PROTEIN as my value for loadedSequences[nSequences].type?

---

You could pass the address of loadedSequences[nSequences].type, and set the string in it quite easily.

Todd

Sorry, didn't see your post. So if i use the address as my argument things should work fine?

You'll still need the char array of sequence. But yes.

heres the code:

Code:

---

10    char content_scan( (char &)sequence)
    {
        int x ;
       
        for(x = 0 ; x < strlen(sequence) ; x++)
            {
                while( sequence[x] )
                    {
                        if( sequence[x] == 'U' )
                            {
                                return "RNA" ;
                                break ;
                            }
                        else if (sequence[x] == 'A' || x == 'C' || x == 'G' || x == 'T')
                            {
                                return "DNA" ;
                                break ;
                            }
                        else
                            {
                                return "PROTEIN" ;
                                continue ;
                            }
                    }
            }
    }               

char *address4content_scan = &loadedSequences[nSequences].data[0] ;
                                 
133    loadedSequences[nSequences].type = content_scan(address4content_scan) ;

---

Still receiving some errors:

beta_seqTool.c:10: error: syntax error before ‘(’ token
beta_seqTool.c: In function ‘main’:
beta_seqTool.c:133: error: incompatible types in assignment


Any suggestions?

Yes.

Code:

---

void content_scan( char * sequence, char * out_field )

---

Code:

---

if( sequence[x] == 'U' )
                            {
                                strcpy(out_field, "RNA" ) ;
                                return ;
                            }
                        else if (sequence[x] == 'A' || x == 'C' || x == 'G' || x == 'T')
                            {
                                strcpy(out_field, "DNA")  ;
                                return ;
                            }
                        else
                            {
                                strcpy(out_field, "PROTEIN")  ;
                                return ;
                            }

---

Code:

---

content_scan( loadedSequences[nSequences].data,  loadedSequences[nSequences].type )

---

You really should learn C before you start messing around with the building blocks of life as we know it...

Code:

---

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

typedef enum { RNA, DNA, Protein, Unknown } SequenceType;

static const char *const NucleotideCodes = "ACGTU";

SequenceType content_scan(const char *sequence)
{
  // First we'll see if it's a protein.
  const char *p = sequence;

  // Go through each code.
  while (p && *p != 0)
  {
      // If the current code is not a nucleotide, obviously it's an amino
      // acid chain and therefore a protein.
      if (strchr(NucleotideCodes, *p) == NULL)
        return Protein;
      ++p;
  }

  // Not a protein, but a nucleotide sequence; only differentiator is
  // uracil vs. thymine.
  // Reset convenience pointer
  p = sequence;
  while (p && *p != 0)
  {
      if (*p == 'U') return RNA;

      if (*p == 'T') return DNA;

      ++p;
  }
  return Unknown;
}

int main()
{
  const char *sequences[] = {
      "AGCGAACUGCCCG", "AGCGAACTGCCCG", "AGMLAHA" } ;

  int i = 0;
  for (; i < (sizeof(sequences) / sizeof(sequences[0])); ++i)
  {
      printf("Result for %s: ", sequences[i]);

      switch(content_scan(sequences[i]))
      {
      case RNA:
        printf("RNA\n");
        break;
      case DNA:
        printf("DNA\n");
        break;
      case Protein:
        printf("Protein\n");
        break;
      case Unknown:
      default:
        printf("Unknown\n");
        break;
      }

  }

  return 0;
}

---

Thanks for the help.

Question: Why couldn't I return the string "DNA" etc directly? Why use "void"?

Can anyone see why this is returning "PROTEIN" when the first is DNA (all ACGT) ?

Code:

---

void content_scan( char * sequence, char * out_field )
    {
        int x ;
       
        for(x = 0 ; x < strlen(sequence) ; x++)
            {
                while( sequence[x] )
                    {
                        if( sequence[x] == 'U' )
                            {
                                strcpy(out_field, "RNA") ;
                                return ;
                            }
                        else if (sequence[x] != 'A' || sequence[x] != 'C' || sequence[x] != 'G' || sequence[x] != 'T' || sequence[x] != EOF || sequence[x] != '\n' )
                            {
                                strcpy(out_field, "PROTEIN") ; 
                                return ;
                            }
                        else
                            {
                                strcpy(out_field, "DNA" ) ;
                                return ;
                            }
                    }
            }
    }

---

Because this:

Code:

---

sequence[x] != 'C'

---

is true.

Perhaps you meant to code

Code:

---

sequence[x+1] != 'C'

---

Why is it evaluating to true? Shouldn't ACGT be skipped?

Quote:

---

Code:

---

for(x = 0 ; x < strlen(sequence) ; x++)
            {
                while( sequence[x] )
                    {
                        if( sequence[x] == 'U' )
                            {
                                strcpy(out_field, "RNA") ;
                                return ;
                            }
                        else if (sequence[x] != 'A' || sequence[x] != 'C' || sequence[x] != 'G' || sequence[x] != 'T' || sequence[x] != EOF || sequence[x] != '\n' )
                            {
                                strcpy(out_field, "PROTEIN") ; 
                                return ;
                            }
                        else
                            {
                                strcpy(out_field, "DNA" ) ;
                                return ;
                            }
                    }
            }

---

---

When sequence[0] is 'A' on the first time through the loop, this fails:

Code:

---

if( sequence[x] == 'U' )

---

So then this multi-condition is evaluated:

Code:

---

else if (sequence[x] != 'A' || sequence[x] != 'C' || sequence[x] != 'G' || sequence[x] != 'T' || sequence[x] != EOF || sequence[x] != '\n' )

---

Is sequence[0] != 'A'? No, (is it equal to 'A'), so this first condition is false, therefore the next condtion is evaluated...

Code:

---

if (sequence[x] != 'C' ) ...

---

Since sequence[0] is not equal to 'C' (it IS equal to 'A'), then this condition is now true (since you said "OR"), thus, "PROTEIN" is returned.

Todd

Quote:

---

Originally Posted by rags_to_riches

You really should learn C before you start messing around with the building blocks of life as we know it...

---

You might want to re-evaulate where the fine line between helping someone and doing their homework for them lies.
Posting a totally rewritten solution doesn't help as much as walking someone through it.

Quote:

---

Originally Posted by gkoenig

Question: Why couldn't I return the string "DNA" etc directly? Why use "void"?

---

You can do that if you make the return type const char*. However, that also means you can't modify your "DNA" string. Otherwise, you would be returning a pointer to a variable that is local to the function. According to scope rules, the local variable would be destroyed when the function returns, thus the function receiving the data would get a pointer to invalid data (garbage).
So to provide a modifiable string, you need to copy it into a proper buffer. And that's why you pass in an argument. But in doing so, there's no need for any return value, thus it's set to void.

Quote:

---

Originally Posted by iMalc

You might want to re-evaulate where the fine line between helping someone and doing their homework for them lies.
Posting a totally rewritten solution doesn't help as much as walking someone through it.

---

Hmmmm...do you think this is homework? If it is, I totally agree with you. A bioinformatics course maybe? If so, shouldn't the OP have had *some* background in programming before being accepted into such a course?

In any event my totally rewritten solution has been even more totally ignored, so I'm not overly concerned. I could argue that it at least shows the correct logic, which seems to be somewhat of a sticking point here.