herbertkb / SimpleLang

A simple language grammar using embedded rule attributes with ANTLR4

SimpleLang

Keith Herbert

A language grammar based on a provided language description/examples with an interpreter implemented with ANTLR as a single grammar file.

Grammar

Syntax Rules

   program     ->  statement*
   statement   ->  declareInt
                   | declareString
                   | declareInferred
                   | assignment
                   | print
                   | NEWLINE

   declareInt      ->  'var' ID {, ID} 'int' ['=' expression] NEWLINE  
   declareString   ->  'var' ID {, ID} 'string' ['=' expression] NEWLINE
   declareInferred ->  ID ':=' (INT|STRING) NEWLINE

   assignment  ->  ID '=' expression NEWLINE
   
   print       ->  'print' expression NEWLINE
   
   expression  ->  '(' expression ')'
                   |   expression OPERATOR expression
                   |   ID
                   |   STRING
                   |   INT      

   

Lexical Rules

   ID -> [a-zA-Z][a-zA-Z0-9]*
   INT -> '-'?[1-9][0-9]*
   NEWLINE -> '\r'?'\n'
   OPERATOR -> ('*' | '/' | '+' | '-')
   TYPE -> 'int' | 'string'
   STRING -> '"'[ a-zA-Z0-9]*'"'

Interpreter

Simply run the provided shell scipt to begin. Finish input with CTRL+D.

$ ./run.sh
generating parser from SimpleLang.g4
compiling parser and lexer
SimpleLang is running. Enter statements. Finish with EOF or CTRL-D
a = 1
b = "hello"
c := b + 1
print c

ello