Editing Recursion
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[[Category:Research]] | [[Category:Research]] | ||
Recursion is a fantastic and often ignored feature of programming languages. Most introductions show an example you'd never use in practice, so this article is my attempt at showing some better ones using Lua. | |||
==Loops== | ==Loops== | ||
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print("You are in a dark room.") | print("You are in a dark room.") | ||
print("Pick a door: fuzzy or metal") | print("Pick a door: fuzzy or metal") | ||
choice = get_choice({fuzzy=1, metal=2}) | choice = get_choice({fuzzy=1,metal=2}) | ||
if choice == 1 then return fuzzy_room() | if choice == 1 then return fuzzy_room() | ||
elseif choice == 2 then return metal_room() | elseif choice == 2 then return metal_room() | ||
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print("This room feels pretty fuzzy...") | print("This room feels pretty fuzzy...") | ||
print("Pick a door: dark, metal") | print("Pick a door: dark, metal") | ||
choice = get_choice({dark=1, metal=2}) | choice = get_choice({dark=1,metal=2}) | ||
if choice == 1 then return dark_room() | if choice == 1 then return dark_room() | ||
elseif choice == 2 then return metal_room() | elseif choice == 2 then return metal_room() | ||
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All the examples on this page use tail calls and run in Lua which implements tail call optimization. This means every program on this page is immune to stack overflows. | All the examples on this page use tail calls and run in Lua which implements tail call optimization. This means every program on this page is immune to stack overflows. | ||
The 1977 [https://en.wikisource.org/wiki/Index:AIM-443.djvu AI Lab Memo 443] talks more broadly about how tail calls are like goto statements that you can pass arguments to. Huge | The 1977 [https://en.wikisource.org/wiki/Index:AIM-443.djvu AI Lab Memo 443] talks more broadly about how tail calls are like goto statements that you can pass arguments to. Huge shoutout to the folks at Wikisource that transcribed this to an accessible text form. | ||
The significant downside of tail call optimization | The significant downside of tail call optimization is that it can make debugging more difficult as you lack a proper stack trace. | ||
==Mainstream support== | |||
Despite mainstream languages slowly adding features from functional languages developed 40 years ago, tail call optimization is still unpopular. I'm guessing that the reason is because not many people see the use of recursion. | |||
== | |||
Despite languages slowly adding features from functional languages developed 40 years ago, tail call optimization is still unpopular. I'm guessing that the reason is because not many people see the use of recursion. | |||
Here's an incomplete list of languages that support it automatically: | Here's an incomplete list of languages that support it automatically: | ||
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* Anything running on WebAssembly | * Anything running on WebAssembly | ||
* Anything JavaScript or transpiling to JavaScript (TypeScript, CoffeeScript) | * Anything JavaScript or transpiling to JavaScript (TypeScript, CoffeeScript) | ||
The situation looks a little bleak at this point. Maybe the future will be better? | |||