Questions about the Lark parser project
Use this tag when asking questions about the Lark parser project (https://github.com/lark-parser/lark)
Questions tagged [lark-parser]
97 questions
15
votes
1 answer
How do you add folding to QsciLexerCustom subclass?
Consider this snippet:
import sys
import textwrap
import re
from PyQt5.Qt import * # noqa
from PyQt5.Qsci import QsciScintilla
from PyQt5.Qsci import QsciLexerCustom
from lark import Lark, inline_args, Transformer
class…
BPL
- 9,632
- 9
- 59
- 117
9
votes
2 answers
How to setup a grammar that can handle ambiguity
I'm trying to create a grammar to parse some Excel-like formulas I have devised, where a special character in the beginning of a string signifies a different source. For example, $ can signify a string, so "$This is text" would be treated as a…
Dima1982
- 189
- 3
- 18
6
votes
1 answer
lark grammar: How does the escaped string regex work?
The lark parser predefines some common terminals, including a string. It is defined as follows:
_STRING_INNER: /.*?/
_STRING_ESC_INNER: _STRING_INNER /(?
flowit
- 1,382
- 1
- 10
- 36
5
votes
2 answers
lark-parser indented DSL and multiline documentation strings
I'm trying to implement a record definition DSL using lark. It is based on indentation, which makes things a bit more complex.
Lark is a great tool, but I'm facing some dificulteis.
Here is a snippet of the DSL I'm implementing:
record Order :
…
Branquif
- 53
- 6
5
votes
2 answers
Priority in grammar using Lark
I have a priority problem in my grammar, and I don't have any more idea to fix it.
I'm using Lark
Here is the thing (I have simplified the problem as much as I can):
from lark import Lark
parser = Lark(r"""
start: set | set_mul
set_mul:…
Kypaz
- 411
- 3
- 11
4
votes
1 answer
Lark how to describe a series of optional tokens
I am parsing a file with a format that can include:
INT32 price min 10 max 100 alertIfSold ;
The min, max and alertIfSold tokens are all optional and can appear in any order. That is
INT32 price max 100 alertIfSold ;
INT32 price …
Eli
- 6,353
- 9
- 30
- 25
4
votes
1 answer
How to balance rules and terminals in python lark parser?
I'm using lark, an excellent python parsing library.
It provides an Earley and LALR(1) parser and is defined through a custom EBNF format. (EBNF stands for Extended Backus–Naur form).
Lowercase definitions are rules, uppercase definitions are…
achedeuzot
- 4,164
- 4
- 41
- 56
3
votes
1 answer
Why do we need to specify the standard Lark lexer to be able to catch comment terminals?
I'm working on a Lark-based project where I need to be able to "catch" comments in the code being parsed.
However it doesn't work when using the standard lexer without explicitly specifying the standard lexer.
I have taken the second example from…
Some programmer dude
- 400,186
- 35
- 402
- 621
3
votes
1 answer
How to prevent lark from recognizing parts of an identifier as a keyword?
I've been experimenting with lark and I came across a little problem.
Suppose I have the following grammar.
parser = Lark('''
?start: value
| start "or" value -> or
?value: DIGIT -> digit
| ID -> id
DIGIT:…
Ushyme
- 140
- 1
- 8
3
votes
1 answer
Lark parsing based on tree location
I am trying to write a Lark grammar and parser to write a DSL on top of numpy. However the Transformer needs to output Python code, not eval that code. So, for example, I'd like to have:
my_parser("max(mat1/mat2, 20) / lag(mat1, 5)")
and this would…
Jonathan
- 1,287
- 14
- 17
2
votes
1 answer
How do I add operator precedence to a lark grammar for FOL with Equality?
How do I modify this grammar so it matches parenthesis that are further away?
?wff: compound_wff
?compound_wff: biconditional_wff
?biconditional_wff: conditional_wff (SPACE? BICONDITIONAL_SYMBOL SPACE? biconditional_wff)*
?conditional_wff:…
Vivek Joshy
- 974
- 14
- 37
2
votes
0 answers
Error in defining closing parenthesis in grammar for C
I am trying to define a simple grammar for C which I am using in Lark. The problem is, I defined the closing parenthesis ("}" or ")") as a terminal in the grammar but it is throwing an error as "No terminal matches ')' in the current parser…
ThunderLord
- 31
- 3
2
votes
1 answer
How can I make this grammar unambiguous?
I'm trying to write a parser for a simple language:
parser = Lark("""
?start: arithmetic_expr | boolean_expr
// relational operation
?rel_op : arithmetic_expr ("<" | ">" | "==" | "!=") arithmetic_expr
// boolean expression
…
Ushyme
- 140
- 1
- 8
2
votes
3 answers
How to parse C++ comments with lark?
How can I write a rule to parse C++ comments either on a line alone or after other code?
I've tried lots of combinations, the latest one being:
?comment: "//" /[^\n]*/ NEWLINE
João M. S. Silva
- 1,078
- 2
- 11
- 24
2
votes
2 answers
Boolean expression parser in lark fails to parse 'a OR b OR c'
This Lark parser is based on this question and this website, but it fails when parsing a OR b OR c.
The website…
rrauenza
- 6,285
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