<!DOCTYPE html>
<html>
<head>
- <title>Title</title>
+ <title>Caesar cipher</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<style type="text/css">
/* Slideshow styles */
+ body {
+ font-size: 20px;
+ }
+ h1, h2, h3 {
+ font-weight: 400;
+ margin-bottom: 0;
+ }
+ h1 { font-size: 3em; }
+ h2 { font-size: 2em; }
+ h3 { font-size: 1.6em; }
+ a, a > code {
+ text-decoration: none;
+ }
+ code {
+ -moz-border-radius: 5px;
+ -web-border-radius: 5px;
+ background: #e7e8e2;
+ border-radius: 5px;
+ font-size: 16px;
+ }
+ .plaintext {
+ background: #272822;
+ color: #80ff80;
+ text-shadow: 0 0 20px #333;
+ padding: 2px 5px;
+ }
+ .ciphertext {
+ background: #272822;
+ color: #ff6666;
+ text-shadow: 0 0 20px #333;
+ padding: 2px 5px;
+ }
+ .indexlink {
+ position: absolute;
+ bottom: 1em;
+ left: 1em;
+ }
</style>
</head>
<body>
<textarea id="source">
-class: center, middle
-
# Caesar ciphers
-* Letter-by-letter enciphering
+
+
+Letter-by-letter enciphering
+
+---
+
+layout: true
+
+.indexlink[[Index](index.html)]
+
+---
+
+# Enciphering and deciphering
+
+## Arithmetic on letters
+
+Convert .plaintext[letter] → .plaintext[number] →
+.ciphertext[number] → .ciphertext[letter]
+
+Functions you will need
+
+```python
+ord()
+
+chr()
+
+%
+```
+
+* What are good test cases?
+
+---
+
+# Using the tools
+
+Before doing anything, create a new branch in Git
+
+* This will keep your changes isolated
+
+Experiment in IPython (ephemeral, for us)
+
+Once you've got something working, copy the code into a `.py` file (permanent and reusable)
+
+```python
+from imp import reload
+
+import test
+reload(test)
+from test import *
+```
+
+Re-evaluate the second cell to reload the file into the IPython notebook
+
+When you've made progress, make a Git commit
+
+* Commit early and often!
+
+When you've finished, change back to `master` branch and `merge` the development branch
---
```python
import string
+
string.ascii_letters
string.ascii_lowercase
string.ascii_uppercase
---
+# DRY and YAGNI
+
+Is your code DRY?
+
+---
+
# Doctest
* Why document?
* Why test?
+```python
+def caesar_encipher_letter(letter, shift):
+ """Encipher a letter, given a shift amount
+
+ >>> caesar_encipher_letter('a', 1)
+ 'b'
+ """
+ if letter in string.ascii_letters:
+ .
+ .
+ .
+```
+
---
# The magic doctest incantation
---
-# Doing all the letters
+# Doing the whole message
+
+## Test-first developement
+
+1. Write the tests.
+ * They will fail. There is no code.
+2. Write code until the tests pass.
+3. Refactor.
+
+---
+
+# Doing the whole message
## Abysmal
ciphertext += caesar_encipher_letter(plaintext[i], key)
```
+Try it in IPython
+
---
-# Doing all the letters
+# Doing the whole message
-## (Merely) Bad
+## Bad
```python
ciphertext = ''
ciphertext += caesar_encipher_letter(p, key)
```
+...but easily generalisable
+
---
-# Doing all the letters
+# Doing the whole message
## Good (but unPythonic)
---
-# Doing all the letters
+# Doing the whole message
## Best
```python
ciphertext = [caesar_encipher_letter(p, key) for p in plaintext]
```
+---
+# Not all iterables are equal
+
+```python
+''.join()
+```
</textarea>
<script src="http://gnab.github.io/remark/downloads/remark-0.6.0.min.js" type="text/javascript">
</script>
<script type="text/javascript">
- var slideshow = remark.create();
+ var slideshow = remark.create({ ratio: "16:9" });
</script>
</body>
</html>
\ No newline at end of file
projects / cipher-training.git / blobdiff