William James schrieb:
I suppose that is Ruby code.
So my statement was correct when I said:
"In some languages it would look a bit cleaner, for example Ruby."
This is because it has a minimal syntax for "lambda".
> def p
> puts "very positive"
> "positive"
> end
> def z
> puts "no no"
> "zero"
> end
> def n
> puts "very negative"
> "negative"
> end
> def nif num, pos, zero, neg
> send( num>0 ? pos : (num==0 ? zero : neg) )
> end
This code would work
> [0, 2.5, -8].map{|x| nif x, :p, :z, :n}
See how you move away from the idea of an if.
Here you need to say :p, :z, :n.
That is not much better as Lisps #'
> ### Another way #####
>
> p = proc {
> puts "very positive"
> "positive" }
> z = proc {
> puts "no no"
> "zero" }
> n = proc {
> puts "very negative"
> "negative" }
> def nif num, pos, zero, neg
> ( num>0 ? pos : (num==0 ? zero : neg) ).call
> end
>
> [0, 2.5, -8].map{|x| nif x, p, z, n}
But will this version also work this way:
[0, 2.5, -8].map{|x| nif x, "p", "z", "n"}
You can't express it like an "if" in Ruby.
In Lisp it is like an IF and represents exactly what
we think.
IF in Lisp:
(if expr
(then-part)
(else-part))
nif in Lisp:
(nif expr
(positive-part)
(zero-part)
(negative-part))
It looks as if it were a construct directly built into Lisp.
If one wants one could even add some additional syntax, so
that it looks like:
(nif expr
positive:
(foo1)
(foo2)
zero:
(foo3)
negative:
(foo4))
If you regard that idea nonsense then I suggest you to not
use Rubys if-statement anymore. But instead program your
own version "RubyIF" so that in future you have to pass all code
inside blocks to your RubyIF function. If you *really* think
that the Lisp savings are not worth it, then you would begin
with my suggestion today.
André
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