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| Related articles |
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| [5 earlier articles] |
| Re: syntax complexity costello@mitre.org (Roger L Costello) (2023-02-20) |
| Re: syntax complexity gah4@u.washington.edu (gah4) (2023-02-20) |
| Re: syntax complexity gneuner2@comcast.net (George Neuner) (2023-02-20) |
| Re: syntax complexity anton@mips.complang.tuwien.ac.at (2023-02-21) |
| syntax complexity christopher.f.clark@compiler-resources.com (Christopher F Clark) (2023-02-21) |
| Re: syntax complexity nmh@t3x.org (Nils M Holm) (2023-02-21) |
| Re: syntax complexity anton@mips.complang.tuwien.ac.at (2023-02-21) |
| Re: ireegular expressions, syntax complexity anton@mips.complang.tuwien.ac.at (2023-02-22) |
| From: | anton@mips.complang.tuwien.ac.at (Anton Ertl) |
| Newsgroups: | comp.compilers |
| Date: | Tue, 21 Feb 2023 18:39:55 GMT |
| Organization: | Institut fuer Computersprachen, Technische Universitaet Wien |
| References: | <AQHZRT1Nf7Ln0mpyG0extuZP9rnVPQ==> 23-02-045 23-02-047 23-02-050 <29156_1676600565_63EEE4F4_29156_1009_1_23-02-051@comp.compilers> 23-02-052 23-02-053 23-02-055 |
| Injection-Info: | gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="31324"; mail-complaints-to="abuse@iecc.com" |
| Keywords: | syntax, lex |
| Posted-Date: | 22 Feb 2023 02:13:28 EST |
anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>Regular expression syntax is missing an operator that signifies the
>intersection of the sets recognized by the operand regexps. Let's
>call this operator "&". Then this requirement for an FP number can be
>expressed as:
>
>([0-9.]*&.*[0-9].*)(E[0-9]+)?&.*[.E].*
...
>[Wouldn't that pattern allow 1.2.3 ? -John]
Good point. The & operator makes it easy to fix this bug (once you
have found it):
([0-9.]*&.*[0-9].*)(E[0-9]+)?&.*[.E].*&[^.]*[.]?[^.]*
But it suggests that I tried to put too many requirements into the
first part, so let's try again:
At most one "." in front of at most one "E": [0-9]*[.]?[0-9]*E?[0-9]*
At least one of "." or "E": .*[.E].*
At least one digit in front of and after "E": .*[0-9].*E[0-9]+
In total:
[0-9]*[.]?[0-9]*E?[0-9]*&.*[.E].*&.*[0-9].*E[0-9]+
- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/
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