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Fix #27 and grammatical fixes

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* Addressing Hashtags and @mentions 

Added both cases in the bonus section

* Minor grammatical fixes

Fixes to issue #27
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Falak 2017-08-01 16:29:35 +05:30 committed by Zeeshan Ahmed
parent 021920c8f9
commit 46af8e3ea0
1 changed files with 4 additions and 3 deletions
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@ -225,7 +225,7 @@ the comma the regular expression `[0-9]{3}` means: Match exactly 3 digits.
## 2.5 Character Group ## 2.5 Character Group
Character group is a group of sub-patterns that is written inside Parentheses `(...)`. As we discussed before that in regular expression Character group is a group of sub-patterns that is written inside Parentheses `(...)`. As we discussed before that in regular expression
if we put a quantifier after a character than it will repeat the preceding character. But if we put quantifier after a character group then if we put a quantifier after a character then it will repeat the preceding character. But if we put quantifier after a character group then
it repeats the whole character group. For example, the regular expression `(ab)*` matches zero or more repetitions of the character "ab". it repeats the whole character group. For example, the regular expression `(ab)*` matches zero or more repetitions of the character "ab".
We can also use the alternation `|` meta character inside character group. For example, the regular expression `(c|g|p)ar` means: lowercase character `c`, We can also use the alternation `|` meta character inside character group. For example, the regular expression `(c|g|p)ar` means: lowercase character `c`,
`g` or `p`, followed by character `a`, followed by character `r`. `g` or `p`, followed by character `a`, followed by character `r`.
@ -328,7 +328,7 @@ regular expressions. The shorthand character sets are as follows:
Lookbehind and lookahead sometimes known as lookaround are specific type of ***non-capturing group*** (Use to match the pattern but not Lookbehind and lookahead sometimes known as lookaround are specific type of ***non-capturing group*** (Use to match the pattern but not
included in matching list). Lookaheads are used when we have the condition that this pattern is preceded or followed by another certain included in matching list). Lookaheads are used when we have the condition that this pattern is preceded or followed by another certain
pattern. For example, we want to get all numbers that are preceded by `$` character from the following input string `$4.44 and $10.88`. pattern. For example, we want to get all numbers that are preceded by `$` character from the following input string `$4.44 and $10.88`.
We will use following regular expression `(?<=\$)[0-9\.]*` which means: get all the numbers which contains `.` character and preceded We will use following regular expression `(?<=\$)[0-9\.]*` which means: get all the numbers which contain `.` character and are preceded
by `$` character. Following are the lookarounds that are used in regular expressions: by `$` character. Following are the lookarounds that are used in regular expressions:
|Symbol|Description| |Symbol|Description|
@ -482,7 +482,8 @@ line. And because of `m` flag now regular expression engine matches pattern at t
* *Date (MM/DD/YYYY)*: `^(0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])[- /.](19|20)?[0-9]{2}$` * *Date (MM/DD/YYYY)*: `^(0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])[- /.](19|20)?[0-9]{2}$`
* *Date (YYYY/MM/DD)*: `^(19|20)?[0-9]{2}[- /.](0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])$` * *Date (YYYY/MM/DD)*: `^(19|20)?[0-9]{2}[- /.](0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])$`
* *MasterCard credit card numbers*: `^(5[1-5][0-9]{14})*$` * *MasterCard credit card numbers*: `^(5[1-5][0-9]{14})*$`
* *Hashtags*: Including hashtags with preceding text (abc123#xyz456) or containing white spaces within square brackets (#[foo bar]) : `\S*#(?:\[[^\]]+\]|\S+)`
* *@mentions*: `\B@[a-z0-9_-]+`
## Contribution ## Contribution
* Report issues * Report issues