On Tue, 2003-10-28 at 22:24, Hiroshi Shinohara wrote:
> Louis, Steve,
> Thank you for your kind explanations.
>
> Steve >The problem is that gen_out() itself knows nothing about it's
> Steve >calling environment and so doesn't know that it's got a generator
> Steve >producing values for its first parameter ...
>
> I see! I must put "procedure" for the argument of gen_out.
>
> ####################
> # write output of generator
> # 1,2,..,10 -> "1 2 3 .. 10"
> # gentest3.icn
>
> procedure main()
> write(g2s(seq,,10))
> end
>
> procedure g2s(gproc,Larg,n_limit,s)
> /s := " " # delimiter
> /Larg := [] # argument of gproc
> s1 := ""
> every s2 := if /n_limit then gproc ! Larg
> else gproc ! Larg \n_limit
> do s1 ||:= (s2 || s)
> return s1[1:-*s]
> end
Hi Hiroshi,
While the above works, that's actually quite a bit of
work that using a co-expression as Louis suggested
avoids. In fact, your problem is a good fit for
a PDCO, (which can be thought of as fancy syntax
to avoid writing 'create'...):
For example, here's a slight varient of your
solution, using a PDCO.
procedure main(args)
gen_out{seq()\10}
end
procedure gen_out(L)
s := [EMAIL PROTECTED] | " "
while writes(@L[1],s)
write()
end
The above solution puts out an extra separator at the
end of the line, but I doubt that's a problem. If
it is, then writing gen_out() as below fixes that
problem:
procedure gen_out(L)
s := [EMAIL PROTECTED] | " "
t := ""
while writes(t, @L[1]) do t := s
write()
end
(there are other ways to fix it). One of the
advantages of using the co-expression is that
you can now use *any* expression to produce
the result sequence, not just a simple procedure
call:
procedure main()
gen_out{2*seq()\10}
end
to produce the first 10 even numbers, for example.
When you want to manipulate result sequences,
co-expressions are a natural way to encapsulate
that result sequence and then act on it.
> I have another question with generator.
> A few weeks ago I wrote a program to generate column numbers
> like MS Excel (A,B,..,Z,AA,AB,..IV).
More on this later, I'm a little pressed for time right now.
--
Steve Wampler <[EMAIL PROTECTED]>
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