Question

Write out a regular expression for C comments in Lex notation.a.Refer to Sec 2.2.3 for further info; b.Show enough details to receive full credits.

Answer 1

comments in c means the lines that start with double slash. so regular expression can be easily written as follows.

(\/*)([^*]|\*+[^*\/])*\*+(\/)

The first bracket holds the pattern "/*"

[^*]\* this part explains that it matches a character except * with a *

+ explains that the patten before it should match one or more times

[^*\/])*\* matches a character except a * and / followed by a star with many number of times

(\/) delimited by a /

so the basic logic here is a sentence that starts with "/*" and ends with "*/" will be matched with any number of stars in between