gdritter repos documents / 5642886
A few new unfinished posts Getty Ritter 8 years ago
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1 ## Idiomatic and Non-Idiomatic Code
2
3 You'll come across a lot of discussions about some bit of code in
4 some language being "idiomatic" or "non-idiomatic". The meaning of
5 this is reasonably clear: it means existing code in that language
6 will do things in a similar way. As a trivial example: looping over
7 a range of numbers in Python is usually done with `for` loops and
8 the `range` function:
9
10 ~~~.python
11 for x in range(10):
12 foo(x)
13 ~~~
14
15 We could, of course, write an effectively identical loop using the
16 `while` function:
17
18 ~~~.python
19 x = 0
20 while x < 10:
21 foo(x)
22 x += 1
23 ~~~
24
25 But in this case, the code in question is much less idiomatic, and
26 for very good reasons: it's more complicated, longer, and easier
27 to screw up (e.g. by forgetting a line or getting a token wrong.)
28 On the other hand, the following is safer and clearer than a
29 while loop, and we'd _still_ consider it unidiomatic Python:
30
31 ~~~.python
32 IntRange(0, 10).each(foo)
33 ~~~
34
35 The above code (assuming we've implemented `IntRange`) is pretty
36 clear and doesn't suffer from the safety problems of the `while`-based
37 code, but it's still not idiomatic. We can conclude that being
38 "idiomatic" isn't just about clarity or convenience or safety: it
39 instead has to do with conforming to technical and social choices
40 within an existing system.
41
42 That raises the question: if we can write code that's safe and clear
43 and concise but still not idiomatic, then what does writing "idiomatic
44 code" buy us?
45
46 ## Why Be Idiomatic?
47
48 There's a strong social advantage to writing idiomatic code: other
49 people are used to reading idiomatic code, so your audience will find
50 your code clearer and easier to read and, above all, _less surprising_.
51
52 But there are strong technical advantages, too:
53
54 ## Idiomatic and Non-Idiomatic Systems
1 I invented a markup language, thus violating a fundamental rule of
2 computer usage:
3
4 *Never invent your own markup language.*
5
6 There are several very good reasons for this rule:
7
8 1. It produces a proliferation of difficult-to-remember standards.
9 What is the syntax for representing italics in MediaWiki markup?
10 In ReStructured Text? Do the rules for enumerated lists differ
11 between GitHub-flavored Markdown and Pandoc-flavored Markdown?
12 Why would you unleash on the world a _new_ standard with
13 subtly _different_ italic syntax?
14
15 2. Parsing is really difficult, and you probably will make a
16 mistake. This is _especially_ tedious for implementation-defined
17 standards: poor
18 [John MacFarlane](http://johnmacfarlane.net/)
19 has to figure out every single unexpected parsing behavior
20 that shows up in
21 [John Gruber's regexp-heavy Markdown script](https://daringfireball.net/projects/markdown/)
22 so he can attempt to
23 [replicate every single edge case](http://pandoc.org/README.html#pandocs-markdown).
24 And we're very lucky that McFarlane cares about this—plenty of formats
25 have weird edge cases in every parser that no other parser replicates
26 perfectly, leading to weird documents that no parser quite gets
27 right and no parser can agree on. (To say nothing of the fact that
28 poorly-written parsers can even be
29 [security risks]()!
30
31 3. Are you _really sure_ that your use-case isn't covered by any
32 of the myriad other markup formats? Are you _really sure_? There
33 are Markdown implementations for every language and they've been
34 tested a lot more thoroughly than whatever you're coming up with.
35
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