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Updated integer regexp to allow for negatives #40

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Updated integer regexp to allow for negatives #40

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3 changes: 1 addition & 2 deletions hangups/javascript.py
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Original file line number Diff line number Diff line change
Expand Up @@ -73,8 +73,7 @@ def _unescape_string(s):

class JavaScriptLexer(purplex.Lexer):
"""Lexer for a subset of JavaScript."""
# TODO: Negative integers
INTEGER = purplex.TokenDef(r'\d+')
INTEGER = purplex.TokenDef(r'[+-]?(?<!\.)\b[0-9]+\b(?!\.[0-9])')
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Can you explain what the regular expression is doing? Why not just [-+]?\d+?

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No, I can't explain it : ) I'm not the best with these. I was going off of the SO link I found + the unit test. I linked it in the PR. There is an explation there.

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[+-]?

one of +, -, or nothing

(?<!\.)

Negative lookbehind, makes sure that a literal dot will not be matched at this position

\b

“the boundary between a word char (\w) and something that is not a word char”

[0-9]+

One or more digit

\b

-''-

(?!\.[0-9])

Negative lookahead, will make sure a literal dot followed by a digit is not matched

All in all, it means that it will match things like 42, +42, and -42, but not floats like 42.6 or .42

FLOAT = purplex.TokenDef(r'[-+]?\d*[.]\d+')

NULL = purplex.TokenDef(r'null')
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1 change: 1 addition & 0 deletions hangups/test/test_javascript.py
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Expand Up @@ -8,6 +8,7 @@
@pytest.mark.parametrize('input_,expected', [
# simple types
('12', 12),
('-1', -1),
('null', None),
('true', True),
('false', False),
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