[xkcd] Functional (27 Sep 2013) - eviltoast

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Functional programming combines the flexibility and power of abstract mathematics with the intuitive clarity of abstract mathematics.

Transcript (from explainxkcd)

[White Hat stands behind Cueball, who is sitting at a computer.] White Hat: Why do you like functional programming so much? What does it actually get you? Cueball: Tail recursion is its own reward.