Question

2. Research to write down the rule of a variable identifier in the following programming languages and write down the regular grammar for that rule. For example, as elaborated in the class, the rule of a variable identifier in C is "start either by or any alphabetic character, and then follow either by_, any alphabetic character, or number", and its regular grammar is: [_a-zA-2] [a-zA-ZO-9]* a. JavaScript i. (5 points) Rule: Solution: ii. (5 points) Regu grammar: Solution: b. PHP (5 points) Rule: i. Solution: (5 points) Regular grammar: i. Solution:

Answer 1

Answer:

a. JavaScript

Rule: Start either by_,$, or any alphabetic character, and then follow either by _,$ any alphabetic character or number

Regular grammer: [_$a-zA-Z] [_$a-zA-Z0-9]*

b. PHP

Rule: All php variables start with $. Their names start either by_, or any alphabetic character, and the follow either by _, any alphabetic character or number

Regular grammer: [$] [_a-zA-Z] [_a-zA-Z0-9]*

c. Scheme

Rule: Their names start with any of these characters ? ! * / < = > : $ % ^ & _ ~ or any alphabetic character, and the follow by any of ? ! . * / < = > : $ % ^ & _ ~ + - @, any alphabetic character or number

Regular grammer: [? ! * / < = > : $ % ^ & _ ~ a-zA-Z] [? ! . * / < = > : $ % ^ & _ ~ + - @a-zA-Z0-9]*

a. GoLang

Rule: Start either by_ or any alphabetic character, and then followed either by _, any alphabetic character or number

Regular grammer: [_a-zA-Z] [_a-zA-Z0-9]*