Algorithm to determine how positive or negative a statement/text is

Question

I need an algorithm to determine if a sentence, paragraph or article is negative or positive in tone... or better yet, how negative or positive.

For instance:

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Answer 1

It's all about context, I think. If you're looking for the people who are best at sucking with SO. Sucking the best can be a positive thing. For determination what is bad or good and how much I could recommend looking into Fuzzy Logic.

It's a bit like being tall. Someone who's 1.95m can considered to be tall. If you place that person in a group with people all over 2.10m, he looks short.