From: Robert Klemme <shortcutter@...>
Date: 2012-12-28T08:27:41+09:00
Subject: Re: numeric?

On Thu, Dec 27, 2012 at 11:32 PM, Brandon Weaver
<keystonelemur@gmail.com> wrote:
> Sorry, I wasn't very clear. I was typing most of that from my Phone.
>
> I'm writing scripts for a wireless ISP, and we use several different types
> of antennas. They're monitored in several different ways,
> SSH/Telnet/SNMP/etc. Annoyingly they all return different values for null,
> but they're always string based, so a numeric evaluation will quickly yield
> whether the device is working or down. I could write a more correct solution
> in the sense that it's less of a hack with individual classes for every
> antenna, but the goal is that if we ever get a new type of equipment that it
> will take minimal coding to get a framework up and running for it.

What's wrong then to use Float() as suggested?

begin
  f = Float(from_device)
  printf "Read value %20.5f\n", f
rescue ArgumentError => e
  # not a float
end

An alternative would be to convert non numeric values to nil - if you
want safe null handling:

f = Float(from_device) rescue nil

> One such example is min, max, and avg for multiple fields such as Signal to
> Noise, Retransmit, and etc. I used instance_variable_get to dynamically
> evaluate fields. There are ways in which I could probably use more of
> Enumerator, and I still need to sort that out some more.

You could use Structs and then:

irb(main):001:0> S=Struct.new :a, :b, :c
=> S
irb(main):002:0> S.members
=> [:a, :b, :c]
irb(main):003:0> S.new.members
=> [:a, :b, :c]
irb(main):004:0> s = S.new 1,2,3
=> #<struct S a=1, b=2, c=3>
irb(main):005:0> s.members
=> [:a, :b, :c]
irb(main):006:0> s.each_pair {|k,v| printf "%p=%p\n", k, v}
:a=1
:b=2
:c=3
=> #<struct S a=1, b=2, c=3>

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/