pickledish / spellcheck

A different™ kind of spell checker, written in Haskell

spellcheck

A different type of spellchecker, written in Haskell.

Inspired by Norvig's spelling corrector. I read this and thought it was cool, but was irritated by what I thought was a glaring omission in the spell checker's design: it didn't take into account key locations.

For example, according to Norvig's corrector, the misspelling vate could be either gate or late with about equal likelihood (since they're both just one edit away from vate). In fact, it would guess 'late', since that's a slightly more common word. However, looking down at our (U.S. layout) keyboard, we immediately see that of course the likelihood isn't equal! The letter v on the keyboard is just one key away from g, whereas it's six letters away from l, so we can clearly see that the person probably meant to type gate but missed the g key with their finger: but v is nowhere near l.

Part of the charm of the Norvig corrector is how short the program is, so I tried to write an equally small program which implemented the idea of key distance to rank the quality of the edits (instead of word frequency, as in the Norvig one).

NOTE, this spellchecker might perform equally terribly as the Norvig corrector, just in very different ways. For example, on input sfore, it ranks afore and score as equally likely corrections, but normal people don't use the word "afore" very much -- they probably wanted "score". I believe one could make a truly great spellchecker by taking both English-language word frequency and key distance into account when suggesting edits, and this is just a demonstration of the latter.

Example

Brandon:spellcheck brandon$ cd src/
Brandon:src brandon$ ghc -O2 main.hs 
[1 of 5] Compiling Keyboard         ( Keyboard.hs, Keyboard.o )
[2 of 5] Compiling Insert           ( Insert.hs, Insert.o )
[3 of 5] Compiling Delete           ( Delete.hs, Delete.o )
[4 of 5] Compiling Replace          ( Replace.hs, Replace.o )
[5 of 5] Compiling Main             ( main.hs, main.o )
Linking main ...
Brandon:src brandon$ ./main sfore
[("afore",1),("score",1),("adore",2),("afire",2),("scored",2)...("pore",16)]

Instructions

No libraries are used other than a modern ghc. Only good for US-layout keyboards!

Compile: Clone the repo and then ghc -O2 main.hs

Run: ./main speling, will return an ugly list of its best guesses for a correction of speling