Thread: undefined reference to `isDigit'

Code:

eugene@eugene-laptop:~/cfiles$ cc 12.12.c
/tmp/cc7U4qkP.o: In function `convertToPostfix':
12.12.c:(.text+0xd6): undefined reference to `isDigit'
collect2: ld returned 1 exit status

Isn't isDigit part of the ctype header?

Code:

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

struct stackNode {
	char data;
	struct stackNode *nextPtr;
};

typedef struct stackNode StackNode;
typedef StackNode *StackNodePtr;


void convertToPostfix( char infix[], char postfix[] );
//isOperator completed
int isOperator( char c );
//precedence completed
int precedence( char operator1, char operator2 );
//push completed
void push( StackNodePtr *topPtr, char value );
//pop completed
char pop( StackNodePtr *topPtr );
char stackTop( StackNodePtr topPtr );
int isEmpty( StackNodePtr topPtr );
void printStack( StackNodePtr topPtr );



int main()
{
	char iFix[ 10 ] = { 0 };
	char pFix[ 10 ] = { 0 };

	convertToPostfix( iFix, pFix );


	return 0;
}




void convertToPostfix( char infix[], char postfix[] )
{
	StackNode *stack = NULL;
	char temp[ 2 ] = ")";
	push( &stack, '(' );

/*   APPENDS ")\0" to the end of infix  */
	strcat( infix, temp );


	while( !isEmpty( stack ) ) {
		if( isOperator( *infix ) ) {

		}

		if ( isDigit( *infix ) ) {
			*postfix = *infix;
			postfix += 2;
		}
		
		if ( *infix == '(' )
			push( &stack, *infix );

		if ( isOperator( *infix ) ) {
			if ( precedence( stackTop( stack ), *infix ) == 0 || precedence( stackTop( stack ), *infix ) == 1 ) {
				*postfix = pop( &stack );
				postfix += 2;
				push( &stack, *infix );
			}
			else
				push( &stack, *infix );
		}

		if ( *infix == ')' ) {
			while ( stackTop( stack ) != '(' ) {
				*postfix = pop( &stack );
				postfix += 2;
			}
			pop( &stack );
		}

		++infix;
	}

}


void printStack( StackNode *topPtr )
{
	while ( topPtr != NULL ) {
		printf( "%c", topPtr->data );
		topPtr = topPtr->nextPtr;
	}

	printf( "\n" );
}


int isEmpty( StackNode *topPtr )
{
	if ( topPtr == NULL )
		return 1;
	else
		return 0;
}


char pop( StackNode **topPtr )
{
	char output;
	StackNode *tempPtr = NULL;

	output = ( *topPtr )->data;
	tempPtr = *topPtr;
	*topPtr = ( *topPtr )->nextPtr;
	free( *topPtr );

	return output;	

}


char stackTop( StackNode *topPtr )
{
	if ( topPtr != NULL )
		return topPtr->data;
	else
		return ' ';

}


void push( StackNode **topPtr, char value )
{
	
	StackNode *newPtr = NULL;
	newPtr = malloc( sizeof( StackNode ) );
	
	if ( newPtr != NULL ) {
		newPtr->nextPtr = *topPtr;
		newPtr->data = value;

		*topPtr = newPtr;
	}
}


int isOperator( char c )
{
	if ( c == '+' || c == '-' || c == '*' || c == '/' || c == '^' || c == '%' )
		return 1;

	else
		return 0;


}


//Determine if precedence of operator1 is greater(1), equal(0), or less then(-1) operator2
int precedence( char operator1, char operator2 )
{
	int opValue[ 2 ] = { 0 };
	char operator[ 2 ];
	operator[ 0 ] = operator1;
	operator[ 1 ] = operator2;
	int i = 0;

	for ( i = 0; i < 2; ++i ) {
		switch( operator[ i ] ) {
			case '+': case '-':
				opValue[ i ] = 1;
				break;
			case '*': case '/': case '%':
				opValue[ i ] = 2;
				break;
			case '^':
				opValue[ i ] = 3;
				break;
			case '(': case ')':
				opValue[ i ] = 4;
				break;
		}

	}



	if ( opValue[ 0 ] > opValue[ 1 ] )
		return 1;
	if ( opValue[ 0 ] == opValue[ 1 ] )
		return 0;
	else
		return -1;
}

ya,C is case sensitive,that's why isDigit and isdigit are two entirely different things.