A Mentoring Course in Smalltalk[0]. I was really surprised, after reading and really loving Design Patterns, that there was still so much to say about OO design. I did love Design Patterns a lot though. Purely Functional Data Structures by Chris Okasaki was also really useful for Haskell, as was Real World Haskell. Programming Prolog probably had a bigger influence on my Prolog than the other books, even though I read Art of Prolog and Prolog Programming in Depth first. Especially the latest edition, it's a really beautiful book. [0]: http://www.lulu.com/us/en/shop/andres-valloud/a-mentoring-co... (http://www.lulu.com/us/en/shop/andres-valloud/a-mentoring-course-on-smalltalk/paperback/product-3788890.html)
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