This is a rather bad article because it completely misses the real complexity of a spell checker. A spell checker is not simply a list of words, it's a way to

This is a rather bad article because it completely misses the real complexity of a spell checker. A spell checker is not simply a list of words, it's a way to check mistakes according to a standard and to point towards ways to fix these mistakes. This not reducible to a look-up in a hashtable. It requires taking into account some complicated things about the definition of a word and the context in which it is written. You might think that's grammar checking but the boundary is not clear and in any case, any language processing application starts with tokenizing and deciding what counts as words and on what basis. What is a word even ? Is "CIA" a word ? What about "C.I.A." ? What about C (as in the language) ? What about c (as in the speed of light) ? 2,4-Dinitrophenylhydrazine ? How does the spellchecker handle dashes and apostrophes ? What about proper nouns ? Really, the example is poorly chosen.