Why I chose Common Lisp over Python, Ruby, and Clojure

Re:Why I chose Common Lisp over Python, Ruby, and Clojure by riobard on Wednesday December 02, 2009 @01:16PM (#972541)

Python's lambda sucks, but that does not necessarily mean map/filter sucks with it too. Of course there are cases where list comprehensions are more convenient and more powerful (esp. if they are more like their "real" counterparts in Haskell and friends). But in cases when map/filter are more convenient, I like the option of using them.

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Re:Why I chose Common Lisp over Python, Ruby, and Clojure by frig on Wednesday December 02, 2009 @01:47PM (#972589)

I'm partially defending list comprehensions here and partially challenging you to consider the possibility that there are higher levels of abstraction out there than those employed by functional programming primitives like map and filter.

Level 0: for-loops with an explicit accumulator

Level 1: map + filter (!)

Level 2: ??? arguably an atemporal set-theoretic approach

In practice in python list comprehensions are a superior syntax for computing with multiple source collections.

(!) Really all you need is reduce

    map = lambda f,l: reduce(lambda h,t: h + f(t), l, [])
    filter = lambda f,l: reduce(lambda h,t: h + t if f(t) else h, l, [])

You'd be silly to implement them that way of course but know your tools.

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Re:Why I chose Common Lisp over Python, Ruby, and Clojure by riobard on Wednesday December 02, 2009 @04:08PM (#972967)

[NOTE: copied from another branch for easy reading for others]

A saner map/filter/product version:

    map(lambda (w,s,l): {'widget': w, 'sprocket': s, 'location': l}
        filter(lambda (w,s,l): l.hasInStock(w) and l.hasInStock(s) and w.isUsableWith(s), 
            product(widgets, sprockets, locations)))

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