On 2013-09-30, Franck Ditter <nob...@nowhere.org> wrote: > In article <ba94102b-18b6-4850-ac85-032b0fe2f...@googlegroups.com>, > rusi <rustompm...@gmail.com> wrote: >> I touched upon these in two blog-posts: >> 1. http://blog.languager.org/2013/06/functional-programming-invades.html >> 2. http://blog.languager.org/2012/10/functional-programming-lost-booty.html >> >> Also most programmers without an FP background have a poor >> appreciation of the centrality of recursion in CS; see >> http://blog.languager.org/2012/05/recursion-pervasive-in-cs.html > > Good approach of FP in Python, but two points make me crazy : > 1. Tail recursion is not optimized. We are in 2013, why ? This > is known technology (since 1960). And don't answer with "good > programmers don't use recursion", this is bullshit.
If you've got a set of recursive functions with recursive calls in tail-call position it's pretty easy to convert to a solution that doesn't blow the stack. Converting to a while loop is usually straightforward, or you try trampolining. If the calls aren't in tail-call position then you wouldn't get tail-call optimization from a language like scheme, either. Getting calls in tail position is often the sticking point, and tail-call optimization doesn't help with that. I think the Python rationale also discusses how it would make tracebacks harder to understand if stackframes could clobber each other. Personally I think that's more a theoretical than a practical problem. Languages with tail-call optimization aren't impossible to debug. > 2. Lambda-expression body is limited to one expression. Why ? > Why the hell those limitations ? In this aspect, Javascript has > a cooler approach. It's in the Design and History FAQ. http://docs.python.org/3/faq/design.html Why cant lambda forms contain statements? Python lambda forms cannot contain statements because Pythons syntactic framework cant handle statements nested inside expressions. However, in Python, this is not a serious problem. Unlike lambda forms in other languages, where they add functionality, Python lambdas are only a shorthand notation if youre too lazy to define a function. Functions are already first class objects in Python, and can be declared in a local scope. Therefore the only advantage of using a lambda form instead of a locally-defined function is that you dont need to invent a name for the function but thats just a local variable to which the function object (which is exactly the same type of object that a lambda form yields) is assigned! What I usually end up with is a dictionary of callbacks, with the simple functions defined in-line and the more complex functions defined just before that and referenced instead. -- Neil Cerutti
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