mirror of
https://github.com/dholerobin/Lecture_Notes.git
synced 2025-03-16 06:10:00 +00:00
215 lines
5.3 KiB
HTML
215 lines
5.3 KiB
HTML
<html>
|
|
<head>
|
|
<style type="text/css">
|
|
.container {
|
|
position: static;
|
|
width: 800px;
|
|
height: 350px;
|
|
overflow: hidden;
|
|
}
|
|
.embed {
|
|
height: 100%;
|
|
width: 100%;
|
|
min-width: 1000px;
|
|
margin-left: -360px;
|
|
margin-top: -57px;
|
|
overflow: hidden;
|
|
}
|
|
body {
|
|
width: 800px;
|
|
margin: auto;
|
|
padding: 1em;
|
|
font-family: "Open Sans", sans-serif;
|
|
line-height: 150%;
|
|
letter-spacing: 0.1pt;
|
|
}
|
|
img {
|
|
width: 90%;
|
|
text-align: center;
|
|
margin: auto;
|
|
box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
|
|
}
|
|
pre, code {
|
|
padding: 1em;
|
|
}
|
|
|
|
table {
|
|
border:1px solid black;
|
|
border-collapse: collapse;
|
|
min-width:60%;
|
|
}
|
|
|
|
th, td{
|
|
border:1px solid black;
|
|
border-collapse: collapse;
|
|
text-align: center;
|
|
}
|
|
|
|
tr:nth-child(even) {background-color: #f2f2f2;}
|
|
|
|
</style>
|
|
<script>
|
|
document.addEventListener('readystatechange', event => {
|
|
if (event.target.readyState === "complete")
|
|
document.activeElement.blur();
|
|
});
|
|
</script>
|
|
|
|
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.18.1/styles/default.min.css">
|
|
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.18.1/highlight.min.js"></script>
|
|
</head>
|
|
<body>
|
|
|
|
|
|
<h2 id="characterswithspecialmeaning">Characters with special meaning</h2>
|
|
|
|
<p>We have seen that, we are using <code>*</code>, <code>+</code>, <code>.</code>, <code>$</code>, etc for different purposes. Now, if we want to match them themselves, we have to escape them using escape character(backslash-\) .</p>
|
|
|
|
<p>Below is the table for these kind of characters and their escaped version, along with their usages.</p>
|
|
|
|
<table>
|
|
<tr>
|
|
<td>Character</td>
|
|
<td>Usage</td>
|
|
<td>Escaped version</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>\</td>
|
|
<td>escape character</td>
|
|
<td>\\</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>.</td>
|
|
<td>predefined character class</td>
|
|
<td>\.</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>|</td>
|
|
<td>OR operator</td>
|
|
<td>\\</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>*</td>
|
|
<td>as quantifier</td>
|
|
<td>\*</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>+</td>
|
|
<td>as quantifier</td>
|
|
<td>\+</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>?</td>
|
|
<td>as quantifier</td>
|
|
<td>\?</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>^</td>
|
|
<td>boundary matcher</td>
|
|
<td>\^</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>$</td>
|
|
<td>boundary matcher</td>
|
|
<td>\$</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>{</td>
|
|
<td>in quantifier notation</td>
|
|
<td>\{</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>}</td>
|
|
<td>in quantifier notation</td>
|
|
<td>\}</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>[</td>
|
|
<td>in character class notation</td>
|
|
<td>\[</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>]</td>
|
|
<td>in character class notation</td>
|
|
<td>\]</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>(</td>
|
|
<td>in group notation</td>
|
|
<td>\(</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>)</td>
|
|
<td>in group notation</td>
|
|
<td>\)</td>
|
|
|
|
</tr>
|
|
<tr>
|
|
<td>-</td>
|
|
<td>range operator</td>
|
|
<td>NA</td>
|
|
|
|
</tr>
|
|
</table>
|
|
|
|
<p>Sometimes, it is also preferred to use escaped forward slash(<code>/</code>).</p>
|
|
|
|
<h2 id="bonusproblems">Bonus Problems</h2>
|
|
|
|
<ol>
|
|
<li><p>Predict the output of the following regex:</p>
|
|
|
|
<p><strong>RegEx:</strong> <code>\b(0|(1(01*0)*1))*\b</code> <br>
|
|
<strong>Text:</strong> <code>This RegEx denotes the set of binary numbers divisible by 3:
|
|
0,11,1010, 1100, 1111, 1001</code></p>
|
|
|
|
<p>Answer: </p>
|
|
|
|
<div class="container">
|
|
<iframe scrolling="no" style="position: absolute; top: -9999em; visibility: hidden;" onload="this.style.position='static'; this.style.visibility='visible';" src="https://regexr.com/4vtqu" class="embed"></iframe>
|
|
</div></li>
|
|
|
|
<li><p>Find a regular expression to match whole lines in the text containing either Apple, Orange, Grape as a word.</p>
|
|
|
|
<p>Hint: Use <code>^</code> and <code>$</code> to match whole lines.</p>
|
|
|
|
<p>Answer: <code>^.*\b(apple|orange|grape)\b.*$</code></p>
|
|
|
|
<div class="container">
|
|
<iframe scrolling="no" style="position: absolute; top: -9999em; visibility: hidden;" onload="this.style.position='static'; this.style.visibility='visible';" src="https://regexr.com/4vtra" class="embed"></iframe>
|
|
</div></li>
|
|
|
|
<li><p>Find an expression which matches <code>cat.</code>, <code>896.</code>, <code>?=++</code> but not <code>abc1</code>.</p>
|
|
|
|
<p>Answer: <code>...\W</code></p>
|
|
|
|
<div class="container">
|
|
<iframe scrolling="no" style="position: absolute; top: -9999em; visibility: hidden;" onload="this.style.position='static'; this.style.visibility='visible';" src="https://regexr.com/4vu8e" class="embed"></iframe>
|
|
</div></li>
|
|
</ol>
|
|
|
|
|
|
<script type="text/javascript">
|
|
document.addEventListener('DOMContentLoaded', (event) => {
|
|
document.querySelectorAll('pre code').forEach((block) => {
|
|
hljs.highlightBlock(block);
|
|
});
|
|
});
|
|
</script>
|
|
</body>
|
|
</html>
|