Comments (3)
No, as in scopes delimited by indented sections of text (al a pug python haskell, etc.)
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significant whitespace
As in multiple contiguous whitespace characters?
OMS -> [\s]:* # optional multi-line whitespace
RMS -> [\s]:+ # required multi-line whitespace
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as in scopes delimited by indented sections of text (al a pug python haskell, etc.)
Ah, so indent / dedent... that will be a context-aware parsing solution.
Use local state
You could get away with creating and updating a local context in the grammar post-processing step, eg.
LINES
-> LINES RBS LINE {% d => {
// where d[0] is the state object
d => updateState(d)
} %}
| LINE {% d => createState(d) %}
RBS -> OWS LF OMS # required break space
OMS -> [\s]:* # optional multi-line space
OWS -> [ \t\r]:* # optional white space
LF -> "\n"
This technique, however, will pose a few challenges and limitations, but it's one way to go about this without creating your own lexer.
Use a custom lexer
This may perhaps be the more trivial way of parsing indent / dedent - as your sneaking suspicion was hinting to. (Haven't tried it myself yet.) I found the following on moo's issue tracker for context-aware indent / dedent parsing: no-context/moo#55 with the last link (moo-indentation-lexer) being the one you probably want.
Then according to the nearley docs:
@{%
const moo = require("moo")
const IndentationLexer = require('moo-indentation-lexer')
// Create a lexer from rules
const mooLexer = moo.compile({ ... })
// Create an indentation-aware lexer using the lexer
const lexer = new IndentationLexer({ lexer: mooLexer })
%}
# Pass your lexer object using the @lexer option:
@lexer lexer
BLOCK -> HEADING %indent STATEMENTS %dedent
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Related Issues (20)
- nearley-unparser binary: rules.map is not a function HOT 3
- Automatic conversion to textmate grammar HOT 1
- Can't undertsand indentifier token HOT 1
- Understanding ambiguity: possible bug with "-" character?
- How to match end of input? HOT 1
- Removing ambiquity by enforcing precedence order HOT 6
- State of discarding tokenizers is sometimes not saved
- Nearley's own grammar is ambiguous?
- The streaming implementation does not take in account that a token may be split across two chunks HOT 4
- Provide a way for users to format their own error messages
- Wrong input lines on error HOT 4
- Use nearley parser at front end, how to reset parser for new input HOT 1
- Parsing the text failed, and the error message said that an opening bracket is required, but I already have an opening bracket. HOT 1
- Docs improvement: what do the colons mean? ":" HOT 2
- Recursive macros does not work HOT 1
- Output is just a nested array of characters HOT 1
- facing an error while parsing in case of newline token HOT 1
- Feature - Support runtime grammar compilation for unit-testing.
- XSS vulnerability through dependency `railroad-diagrams` HOT 1
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