[Tutor] Passing perimeters in dictionary values?

[spir]

Le Wed, 25 Feb 2009 00:01:49 -0000,
"Alan Gauld" <alan.gauld at btinternet.com> s'exprima ainsi:

> 
> "nathan virgil" <sdragon1984 at gmail.com> wrote 
> 
> > I'm not familiar with lambdas yet, and I don't think this book will
> > introduce me to them; they aren't listed in the index, anyway.
> 
> lambda is just a fancy mathematical name for a simple 
> concept - its a block of code, like the body of a function.
> In Python its even simpler, it is an expression. And we 
> store that expression and make it callable.
> 
> 
> def funcname(aParam):
>       return <expression using aParam>
> 
> is the same as
> 
> funcname = lambda aParam: <expression using aParam>
> 
> In some languages, including some Lisp dialects function 
> definitions are syntactic sugar for exactly that kind of lambda 
> assignment. Some even make it explicit as in:
> 
> (define func
>        ( lambda (aParam) 
>              (expression using aParam)))

In io (a wonderful prototype-based languages which syntax reflects the code structure (read: parse tree) like in Lisp), you would have:

method_name := method(aParam, <expression using aParam>)

for instance:

perimeter := method(radius, 2 * PI * radius)
average := method(values,
	sum := values sum
	sum / values count
	)

[Above: there is not '.' -- return value needs not be explicit]

> In Python its more like the other way around, functions are 
> defined using def and lambdas are really syntax wrapped 
> around that. 
> 
> lambdas are often offputting to beginners but they are useful 
> in avoiding lots of small oneliner type functions (and the resultant 
> namespace clutter) and they are very important in understanding
> the theory behind computing (ie. Lambda calculus).
> 
> HTH,
> 
> 


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