1. Pgm #1 Infix to Postfix Common Problems/Issues/Mistakes

2. #1 I don’t know how to use getToken getToken returns the next token via a string array as its second parameter. (You don’t have to pass an address since C already does that for arrays.) getToken is passed a pointer (as the first parameter) which represents the current position in the text line. getToken must have a mechanism to advance in the text line. It functionally returns the next position. That is a pointer to the position after the token. On a subsequent call, you must pass that new position as the first parameter in the next call. Look at the example on the bottom of the stacksArray.docx. One of the reasons for that example is to show how to use getToken.

3. #2 What do I pass to categorize? Categorize modifies an Element structure // Element typedef used for Element values placed in the stack or out array typedef struct { Token szToken; // Could be a variable, numeric constant, operator, // left parenthesis or right parenthesis int iCategory; // A value used to make it easier to handle // different cases for the types of tokens int iSubcategory; // If the category is CAT_OPERAND, this // specifies whether it is a VARIABLE or a CONSTANT. int iPrecedence; // An integer representing the operator // precedence. Higher values imply // higher precedence. } Element;

4. #2 What do I pass to categorize? (continued) It must be passed the address of an Element structure. A common mistake: Element element; … while (pszInfix != NULL) { categorize(element); The compiler will say something about the Element structure doesn’t match a pointer to an element structure. Next common mistake: Element *pElement; … while (pszInfix != NULL) { categorize(pElement);

5. #2 What do I pass to categorize? (continued) We really need to pass the address of the an Element structure: Element element; … while (pszInfix != NULL) { categorize(&element); Make certain element.szToken has the current token.

6. #3 Not understanding the algorithm before attempting to code it Make certain you understand how the algorithm works conceptually before you code. Follow an example on the board.

7. #4 My program doesn’t work, what do I do? A debugger (e.g., ddd) is one of the most important tools you can use. One student had code like the following with a subtle bug: pszText = getToken(pszText, szToken, MAX_TOKEN); while (pszText != NULL); { categorize(&element); switch(element.iCategory) { case CAT_OPERAND: addOut(out, element); break; case CAT_LPAREN: push(stack, element); break;

8. #5 The pain of carriage returns Linux places only a new line character (\n) after the end of each line. Microsoft Windows has both a new line character (\n) and a carriage return (\r) at the end of each line. If you copy/paste text lines from Windows to Linux, you might get carriage returns in your file. You must remove them. On my setup page: How can I remove carriage returns (\r) from Microsoft files on linux? To see if a file contains carriage returns: cat filename | od -c To remove carriage returns from a file: sed -i 's/\r//' filename

9. #5 The pain of carriage returns (continued) To remove carriage returns from a file: sed -i 's/\r//' filename

10. #6 Not asking for help I took this job to help students. That is what I enjoy doing! Since tutors and TAs might not be familiar with your assignment and course notes, before asking a TA or tutor: Read the assignment. Examine the.h file. Examine the provided input files Examine the driver. Look for relevant information in the course notes. Print out all of those files

11. #7 Starting late  less time to ask for help