I know it's HN folklore to claim "Trivial! Would do over a weekend!", but please...
Doing a half-decent production spell checker is STILL a major feat. Same as "just crawling the web" (further down the discussion). Both require problem understanding and engineering you can't see and appreciate at a glance.
And no, looking up individual words in some predefined dictionary doesn't qualify as half-decent spell checking, especially for non-English languages. Spelling correction is another step.
Doing a half-decent production spell checker is STILL a major feat. Same as "just crawling the web" (further down the discussion). Both require problem understanding and engineering you can't see and appreciate at a glance.
And no, looking up individual words in some predefined dictionary doesn't qualify as half-decent spell checking, especially for non-English languages. Spelling correction is another step.