Add anchors

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Zeeshan Ahmed 2017-07-24 11:24:48 +01:00
parent 63301d61ec
commit 6b1ff1f55a

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@ -31,11 +31,10 @@ contains uppercase letter and also it is too short.
- [Character Group]()
- [Alternation]()
- [Escaping special character]()
- [Quantifiers]()
- [OR operator]()
- [Character Sets]()
- [Anchors]()
- [Caret]()
- [Dolar]()
- [Shorthand Character Sets]()
- [Grouping]()
- [Lookaheads]()
- [Flags]()
@ -215,4 +214,40 @@ expression `[f|c|m]at\.?` means: lowercase letter `f`, `c` or `m`, followed by l
<pre>
"[f|c|m]at\.?" => The <a href="#learn-regex"><strong>fat</strong></a> <a href="#learn-regex"><strong>cat</strong></a> sat on the <a href="#learn-regex"><strong>mat.</strong></a>
</pre>
## 2.7 Anchors
In regular expression to check if the matching symbol is the starting symbol or endnig symbol of the input string for this purpose
we use anchors. Anchors are of two types: First type is Caret `^` that check if the matching character is the character of the input and the
second type is Dolar `$` that checks if matching character is the last character of the input string.
### 2.7.1 Caret
Caret `^` symbol is use to check if matching character is the first character of the input string. If we apply the following regular
expression `^a` (if a is the starting symbol) to input string `abc` it matches `a`. But if we apply regular expression `^b` on above
input string it does not match anything. Beacause in input string `abc` "b" is not the starting symbol. Lets take a look on another
regular expression `^[T|t]he` which means: uppercase character `T` or lowercase character `t` is the start symbol of the input string,
followed by lowercase character `h`, followed by lowercase character `e`.
<pre>
"[T|t]he" => <a href="#learn-regex"><strong>The</strong></a> car is parked in <a href="#learn-regex"><strong>the</strong></a> garage.
</pre>
<pre>
"^[T|t]he" => <a href="#learn-regex"><strong>The</strong></a> car is parked in the garage.
</pre>
### 2.7.2 Dolar
Dolar `$` symbol is use to check if matching character is the last character of the input string. For example regular expression
`(at.)$` means: lowercase character `a`, followed by lowercase character `t`, followed by anything except new line and the matcher
must be end of the string.
<pre>
"(at.)" => The f<a href="#learn-regex"><strong>at </strong></a>c<a href="#learn-regex"><strong>at </strong></a>s<a href="#learn-regex"><strong>at </strong></a>on the m<a href="#learn-regex"><strong>at.</strong></a>
</pre>
<pre>
"(at.)$" => The fat cat sat on the m<a href="#learn-regex"><strong>at.</strong></a>
</pre>