Exercise 6-1. Our version of getword does not properly handle underscores, string constants, comments, or preprocessor control lines. Write a better version. K&R’s getword from Section 6.3 reads the next identifier or non-alphabetic character from input, but has four gaps: Underscores: valid in C identifiers (_var, size_t) but the original checks only isalpha String constants: …
Exercise 5-20. Expand dcl to handle declarations with function argument types, qualifiers like const, and so on. The basic dcl treats () as “function returning” but ignores argument types. This exercise adds: parameter lists inside (), type qualifiers (const, volatile), storage classes (static, extern), and the void type. The approach: when ( is encountered and …
Exercise 5-19. Modify undcl so that it does not add redundant parentheses to expressions. K&R’s undcl (Section 5.12) converts English descriptions back into C declarations. The original adds parentheses around every pointer-to-function construct, even when they are not needed. A pointer to a function needs parentheses — int (*fp)(); a simple pointer does not — …
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 5-17. Add a field-handling capability, so sorting may be done on fields within lines, each field sorted according to an independent set of options. (The index for this book was sorted with -df for the index category and -n for the page numbers.) Fields are whitespace-delimited columns. The syntax -k<field>[flags] selects a 1-based field …
Exercise 5-15. Add the option -f to fold upper and lower case together, so that case distinctions are not made during sorting; for example, a and A compare equal. Add a fold flag. When set, the comparison function converts both characters to lowercase before comparing. The key: don’t modify the strings themselves — do the …