Calling an anonymous function

ruby-talk
1

Hi All,

In plain Pascal, I can do this:
  
type
   RealFunction = function(x: double): double;

function bisect(f: RealFunction; a, b: double): double;
begin
   if (abs(f(a)) < 0.001) then result := a
   else if (abs(f(b)) < 0.001) then result := b
   else begin
     // find the solution inside the interval
   end;
end;

So I can declare functions like these...

function f(x: double): double;
begin
   result := sin(x) - 0.5;
end;

function g(x: double): double;
begin
   result := x*x*x-10;
end;

... and call them this way:

var
   x1, x2: double;
begin
   x1 := bisect(f,0,pi/2);
   x2 := bisect(g,1,3);
   ...
end.

I have tried many ways to write this in Ruby but I failed to get it working as expected. Any hint?
Thank you.

2

My bad, answered to the wrong thread. Sorry for the inconvenience.

- - - - Original reply follows - - - - - -

Maybe you are looking for #lambda?

···

----------------------------------------
anon_method = lambda do |x|
  x + 2
end

anon_method.call(4) #=> 6
----------------------------------------

Vale,
Quintus

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3

This would be the way to go. One can also invoke the method via #:

irb(main):001:0> anon_method = lambda do |x|
irb(main):002:1* x + 2
irb(main):003:1> end
=> #<Proc:0x00000600418f60@(irb):1 (lambda)>
irb(main):004:0> anon_method[9]
=> 11

Basically with that approach anything that implements # or #call can be used:

irb(main):005:0> Pluser = Struct.new :add do
irb(main):006:1* def call(x) x + add end
irb(main):007:1> alias call
irb(main):008:1> end
=> Pluser
irb(main):009:0> f = Pluser.new 2
=> #<struct Pluser add=2>
irb(main):010:0> f[9]
=> 11
irb(main):011:0> f.call(9)
=> 11

Sorry for the bad class naming. :slight_smile:

Kind regards

robert

···

On Sun, May 4, 2014 at 5:51 PM, Quintus <quintus@quintilianus.eu> wrote:

My bad, answered to the wrong thread. Sorry for the inconvenience.

- - - - Original reply follows - - - - - -

Maybe you are looking for #lambda?

----------------------------------------
anon_method = lambda do |x|
  x + 2
end

anon_method.call(4) #=> 6
----------------------------------------

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