rbnf-rts

Runtime support for generated parsers of RBNF.hs

P.S:

rbnf-rts is the new fastest Python parser generator by 2020, according to a benchmark given by benchmark-json.

This package has come to the end of its lifetime.

frontend-for-free is now the state of the art, and also inherits all features of RBNF with simpler and more expressive BNF notations.

frontend-for-free uses the same underlying compiler as RBNF, but provided with better user interface.

Features

• Syntax-driven
• Left recursion with LL parsing(yes, left recur in LL, it's right)
• Grammar inline optimizations
• Smarter lookahead via ID3 algorithm
• Statically generated(no need to create the parser again and again when starting your application)
• Good error reports(including the position and nested rule names of parsing error)
• RBNF.hs is language independent
• [WIP]: context sensitive parsing as an extension to CFG

More Examples

Check the test directory:

• test
  • multiply : parser/lexer implementation for multiplications
  • arith : parser/lexer implementation for arithmetics
  • relax : parser/lexer implementation for a full-featured programming language
  • llvmir: parser/lexer implementation for LLVM IR, nearly full-featured
  • rbnfjson: a json parser implemented by RBNF.hs and rbnf-rts

In each sub-directory of test, you can run tests via directly invoking the test.sh., like cd test/llvmir && bash test.sh

Native Dependencies

• The Haskell Stack Toolchain

• The executable rbnf-pgen in PATH.

  If ~/.local/bin is already in PATH:

  git clone https://github.com/thautwarm/RBNF.hs
  cd RBNF.hs
  stack install .
  

Example: Multiplications

1. write a multiply.exrbnf file

# 'mul' is a python global which should be marked as 'required' in .rlex
Mul    : lhs=Mul "*" rhs=Atom { mul(lhs, rhs) }
       | a=Atom  {a}
       ;

# 'unwrap' should be marked as 'required', just as 'mul'
Atom   :  "(" !a=Mul ")"  {a} ;
       |  <number>        { unwrap($0) };
START ::= <BOF> Mul <EOF> { $1 };

or write a multiply.rbnf file:

# 'mul' is a python global which should be marked as 'required' in .rlex
Mul    : !lhs=Mul "*" !rhs=Atom            -> mul(lhs, rhs);
Mul    : !a=Atom                           -> a;
Atom   : "(" !a=Mul ")"                    -> a;

# 'unwrap' should be marked as 'required', just as 'mul'
Atom   : !a=<number>                       -> unwrap(a);
START ::= <BOF> !a=Mul <EOF>               -> a;

2. write a multiply.rlex file:

%require mul
%require unwrap
%ignore space
number [+-]?\d+
space \s+

3. codegen

sh> rbnf-pygen multiply.rbnf multiply.rlex multiply.py --k 1 --traceback

4. run statically-generated parsers and lexers and enjoy its efficiency

from rbnf_rts.rts import Tokens, State
from multiply import run_lexer, mk_parser
import operator

def unwrap(x: Token):
    return int(x.value)

scope = dict(mul=operator.mul, unwrap=unwrap)

parse = mk_parser(**scope)


tokens = list(run_lexer("<current file>", "-1 * 2 * (3 * 4)"))
got = parse(State(), Tokens(tokens))
print(got)

Got (True, -24), where True indicates the parsing succeeded.

If False, a list of errors will be given in the second element of the return tuple.

5. Menhir-like syntax sugars including list and separated_list.

A json parser more than 20% efficient than that of lark-parser(lol), written as a .exrbnf file.

START: <BOF> value <EOF> { $1 };

value: <ESCAPED_STRING> { DQString(*$0) }
     | <SIGNED_INT>     { int(*$0) }
     | <SIGNED_FLOAT>   { float(*$0) }
     | "true" { True }
     | "null" { None }
     | "false" { False }
     # array
     | '[' ']' {[]}
     | '[' separated_list(',', value) ']' { $1 }
     # object
     | '{' '}' { dict() }
     | '{' separated_list(',', pair) '}' { dict($1) }
     ;
pair   : <ESCAPED_STRING> ":" value { (DQString(*$0), $2) };

Check rbnfjson for more information.