Hiring guide for ANTLR2 Engineers

ANTLR2 Developer Hiring Guide

ANTLR2 is a powerful software programming language developed by Terence Parr at the University of San Francisco in 1992. It's an acronym for ANother Tool for Language Recognition, and it's primarily used to construct recognizers, interpreters, compilers and translators. ANTLR provides a framework for constructing recognizers, interpreters, compilers and translators from grammatical descriptions containing Java actions. The language has been widely adopted due to its flexibility in handling translation tasks with complex syntaxes. Its development was driven by the need for a tool that combines all aspects of compiler construction into one package (Parr & Quong 1995).

Ask the right questions secure the right ANTLR2 talent among an increasingly shrinking pool of talent.

First 20 minutes

General ANTLR2 app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in ANTLR2 application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you define ANTLR2?
ANTLR2 is a powerful parser generator for reading, processing, executing, or translating structured text or binary files. It's widely used to build languages, tools, and frameworks.
What are the key features of ANTLR2?
ANTLR2 has several key features such as support for tree construction, tree walking, translation, error recovery, and it also generates dependency graphs.
Describe the difference between ANTLR2 and ANTLR4.
ANTLR4 has several improvements over ANTLR2. It has better support for left-recursive grammars, a more powerful syntax, and improved error handling.
How would you use ANTLR2 to create a lexer and parser for a simple language?
First, you would define the grammar for the language. Then, you would use ANTLR2 to generate the lexer and parser. You would then write a driver program to use the lexer and parser to process input.
What are the steps to generate a parser using ANTLR2?
The steps to generate a parser using ANTLR2 are: define the grammar, run ANTLR2 on the grammar to generate the lexer and parser, compile the lexer and parser, and then use them in your program.
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What you’re looking for early on

Does the candidate have a solid understanding of ANTLR2?
Has the candidate worked on projects involving ANTLR2?
Can the candidate solve problems using ANTLR2?
Is the candidate able to explain complex ANTLR2 concepts in simple terms?

Next 20 minutes

Specific ANTLR2 development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between a lexer and a parser in ANTLR2.
A lexer in ANTLR2 is used to convert input text into tokens, while a parser is used to process those tokens according to the grammar rules.
How would you handle errors in ANTLR2?
ANTLR2 provides several mechanisms for error handling, such as generating default error messages, overriding the error reporting methods, and defining your own error handling routines.
What are the types of parsers that can be generated by ANTLR2?
ANTLR2 can generate LL(k) parsers, which are a type of recursive descent parser. It can also generate tree parsers.
Describe the difference between LL and LR parsing.
LL parsing is top-down, starting from the start symbol and trying to match the input, while LR parsing is bottom-up, starting from the input and trying to reach the start symbol.
How would you use ANTLR2 to generate a parser for a language with left-recursive grammar rules?
ANTLR2 does not natively support left-recursive grammar rules. You would need to rewrite the grammar to eliminate left recursion before using ANTLR2 to generate the parser.
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The ideal back-end app developer

What you’re looking to see on the ANTLR2 engineer at this point.

At this point, a skilled ANTLR2 engineer should demonstrate strong problem-solving abilities, proficiency in ANTLR2 programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with ANTLR2.

What does this simple ANTLR2 grammar do?
grammar Hello;

r  : 'hello' ID ;

ID : 'a'..'z'+ ;

WS : (' '|'
') {$channel=HIDDEN;} ;
This is a simple ANTLR2 grammar that matches the word 'hello' followed by an identifier. The identifier is defined as one or more lowercase letters. Whitespace characters are ignored.
What does this ANTLR2 grammar do?
grammar Expr;

prog:   stat+ ;

stat:   expr NEWLINE
    |   ID '=' expr NEWLINE
    |   NEWLINE ;

expr:   multExpr (('+'|'-') multExpr)*
    |   INT ;

multExpr : atom ('*' atom)* ;

atom:   INT
    |   ID
    |   '(' expr ')' ;

ID  :   'a'..'z'+ ;

INT :   '0'..'9'+ ;

NEWLINE:'\r'? '\n' ;

WS  :   (' '|'	')+ {$channel=HIDDEN;} ;
This ANTLR2 grammar defines a simple calculator that can evaluate expressions with addition, subtraction, and multiplication. It also supports variable assignment.
What does this ANTLR2 grammar do?
grammar Array;

prog:   stat+ ;

stat:   array NEWLINE
    |   NEWLINE ;

array:  '[' values ']' ;

values: INT (',' INT)* ;

INT :   '0'..'9'+ ;

NEWLINE:'\r'? '\n' ;

WS  :   (' '|'	')+ {$channel=HIDDEN;} ;
This ANTLR2 grammar defines a simple array syntax. It matches an array of integers, separated by commas and enclosed in square brackets.
What does this ANTLR2 grammar do?
grammar Threads;

prog:   stat+ ;

stat:   'thread' ID '{' (command ';')+ '}' NEWLINE
    |   NEWLINE ;

command: ID '=' expr
    |   'print' expr ;

expr:   INT
    |   ID ;

ID  :   'a'..'z'+ ;

INT :   '0'..'9'+ ;

NEWLINE:'\r'? '\n' ;

WS  :   (' '|'	')+ {$channel=HIDDEN;} ;
This ANTLR2 grammar defines a simple threading language. It supports thread creation, variable assignment, and print commands within threads.

Wrap-up questions

Final candidate for ANTLR2 Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle ANTLR2 application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the limitations of ANTLR2?
Some limitations of ANTLR2 are that it does not natively support left-recursive grammars, and it can be difficult to use for complex languages.
Describe the difference between a parse tree and an abstract syntax tree.
A parse tree represents the entire parse according to the grammar, including all tokens, while an abstract syntax tree represents the semantic structure of the code, abstracting away syntactic details.
How would you use ANTLR2 to generate a tree parser?
To generate a tree parser with ANTLR2, you would first generate a parser that builds a parse tree. Then, you would define a tree grammar and use ANTLR2 to generate the tree parser.

ANTLR2 application related

Product Perfect's ANTLR2 development capabilities

Beyond hiring for your ANTLR2 engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in ANTLR2 projects, and can engage in multiple capacities.