Exercise 5-18. Make the basic dcl program recover from input errors. K&R’s dcl program (Section 5.12) parses C declarations into English. It calls error() which prints a message and then exits — making it useless for batch input. The fix: on error, skip to the next newline and try to continue. This requires turning dcl‘s …
Exercise 5-12. Extend entab and detab to accept the shorthand entab -m +n to mean tab stops every n columns, starting at column m. Choose convenient (for the user) default behavior. Two new argument forms extend the programs from Exercise 5-11: -m sets the starting column and +n sets the interval. So detab -4 +3 …
Exercise 5-11. Modify the programs entab and detab (written as exercises in Chapter 1) to accept a list of tab stops as arguments. Use the default tab settings if there are no arguments. The Chapter 1 versions of entab and detab used a fixed tab width of 8. This version reads tab stop positions from …
Exercise 5-7. Rewrite readlines to store lines in an array supplied by main, rather than calling alloc to maintain storage itself. How much faster is the program? The K&R readlines from Section 5.6 calls a custom alloc to carve space out of a static buffer. This exercise moves storage to a flat char linestore[] array …
Exercise 5-6. Rewrite appropriate programs from earlier chapters and exercises with pointers instead of array indexing. Good possibilities include getline (Chapters 1 and 4), atoi, itoa, and their variants (Chapters 2, 3, 4), reverse (Chapter 3), strindex and getop (Chapter 4). This exercise is about translation: every array subscript a[i] can be written as *(a+i), …
Exercise 5-4. Write the function strend(s,t), which returns 1 if the string t occurs at the end of the string s, and zero otherwise. Advance both pointers to their respective null terminators, then walk backwards together comparing characters. If t runs out first (pointer reaches the start of t), every character matched — t is …