Asp Forum - case statement and ranges

Mini Skirt

8/13/2008 10:21:00 PM

Hey, I want to do something like that:

case amount
when 25..50: 42
when 51..66: 78
when 90..123: 99
end

which works of course.

Now what I would like to have some other cases like when amount is lower
that 25, but with no minimum, or when it is higher that 123 ...
I could write something like:

case
when amount === (25..50): 42
when amount === (51..66): 78
when amount === (90..123): 99
when amount < 25: 100
when amount > 123: 200
else 0 # this would happen only when amount is in 67...90
end

But it doesn't feel that well ... since I am repeating my amount
variable all the time and this is precisely what the 'case something'
construct is about.

I cold also use some extremely high and extremely low values in ranges,
like (123..100000000) or (-10000000..25) to handle the other cases since
I know that in my use, it would be fine. But it does look quite
inelegant ....

thx
--
Posted via http://www.ruby-....

9 Answers

ara.t.howard

8/13/2008 10:45:00 PM

On Aug 13, 2008, at 4:21 PM, Mini Skirt wrote:

> Hey, I want to do something like that:
>
> case amount
> when 25..50: 42
> when 51..66: 78
> when 90..123: 99
> end
>
> which works of course.
>
> Now what I would like to have some other cases like when amount is
> lower
> that 25, but with no minimum, or when it is higher that 123 ...
> I could write something like:

the basis of a solution:

cfp:~ > cat a.rb

case 42
when all(:a, :b, :c)
puts 'nope'

when any(42, 43, 44)
puts 'forty-two'
end

case 42
when any
puts 42
end

case 42.0
when any( 25 .. 50, any )
p 42.0
when 51 .. 66
when 90 .. 123
end

case 4.2
when any( 25 .. 50, any )
p 4.2
when 51 .. 66
when 90 .. 123
end

BEGIN {

class Pattern < ::Array
def initialize *elements
replace elements unless elements.empty?
end

def inspect
"#{ self.class.name }#{ super }"
end

class Any < Pattern
def === other
return true if empty?
any?{|element| element === other}
end
alias_method '==', '==='
end

class All < Pattern
def === other
return false if empty?
all?{|element| element === other}
end
alias_method '==', '==='
end
end

def all(*a, &b) Pattern::All.new(*a, &b) end
def any(*a, &b) Pattern::Any.new(*a, &b) end

}

cfp:~ > ruby a.rb
forty-two
42
42.0
4.2

a @ http://codeforp...
--
we can deny everything, except that we have the possibility of being
better. simply reflect on that.
h.h. the 14th dalai lama

Ryan Davis

8/14/2008

I agree that your second example doesn't feel right... I prefer
altering your original example:

case amount
when 25..50: 42
when 51..66: 78
when 90..123: 99
else amount < 25 ? 100 : 200
end

Todd Benson

8/14/2008 12:29:00 AM

On Wed, Aug 13, 2008 at 6:59 PM, Ryan Davis <ryand-ruby@zenspider.com> wrote:
> I agree that your second example doesn't feel right... I prefer altering
> your original example:
>
> case amount
> when 25..50: 42
> when 51..66: 78
> when 90..123: 99
> else amount < 25 ? 100 : 200
> end

Don't use this; it's just for fun...

my_number = 57
begin
[25, 51, 67, 90, 123].zip([100, 42, 78, 0, 99]).select {|a| a[1] if
my_number < a[0]}.first[1] rescue 200
end

Two things.

1. It's generally not good form to use a rescue for program logic

2. I'm surprised that no one saw the fundamental problem in using
ranges. We're looking at a line that has divisions, not pieces that
may or may not overlap. I suppose if you were clever, you could make
it work and have it behave almost the way you want it to.

I'd go with dividers instead of ranges. You could build your ranges
automagically with a list of the divisions, I suppose.

Even though at first glance it seems verbose, I do like Ara's
solution. And Ryan Davis' crack is really simple and succinct. Like
them both!

Todd

Joel VanderWerf

8/14/2008 2:26:00 AM

Mini Skirt wrote:
> Hey, I want to do something like that:
>
> case amount
> when 25..50: 42
> when 51..66: 78
> when 90..123: 99
> end
>
> which works of course.
>
> Now what I would like to have some other cases like when amount is lower
> that 25, but with no minimum, or when it is higher that 123 ...
> I could write something like:
>
> case
> when amount === (25..50): 42
> when amount === (51..66): 78
> when amount === (90..123): 99
> when amount < 25: 100
> when amount > 123: 200
> else 0 # this would happen only when amount is in 67...90
> end
>
> But it doesn't feel that well ... since I am repeating my amount
> variable all the time and this is precisely what the 'case something'
> construct is about.
>
> I cold also use some extremely high and extremely low values in ranges,
> like (123..100000000) or (-10000000..25) to handle the other cases since
> I know that in my use, it would be fine. But it does look quite
> inelegant ....
>
> thx

Big numbers are more elegant if they are big enough:

Infinity = 1/0.0
amount = 456
p case amount
when 25..50: 42
when 51..66: 78
when 90..123: 99
when -Infinity..25: 100
when 123..Infinity: 200
end

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

elliottcable

8/14/2008 2:31:00 AM

I always throw this in my core_ext:

> class Float
> Infinity = 1.0/0.0
> end

On Aug 13, 2008, at 6:26 PM, Joel VanderWerf wrote:

> Mini Skirt wrote:
>> Hey, I want to do something like that:
>> case amount
>> when 25..50: 42
>> when 51..66: 78
>> when 90..123: 99
>> end
>> which works of course.
>> Now what I would like to have some other cases like when amount is
>> lower
>> that 25, but with no minimum, or when it is higher that 123 ...
>> I could write something like:
>> case
>> when amount === (25..50): 42
>> when amount === (51..66): 78
>> when amount === (90..123): 99
>> when amount < 25: 100
>> when amount > 123: 200
>> else 0 # this would happen only when amount is in 67...90
>> end
>> But it doesn't feel that well ... since I am repeating my amount
>> variable all the time and this is precisely what the 'case something'
>> construct is about.
>> I cold also use some extremely high and extremely low values in
>> ranges,
>> like (123..100000000) or (-10000000..25) to handle the other cases
>> since
>> I know that in my use, it would be fine. But it does look quite
>> inelegant ....
>> thx
>
> Big numbers are more elegant if they are big enough:
>
> Infinity = 1/0.0
> amount = 456
> p case amount
> when 25..50: 42
> when 51..66: 78
> when 90..123: 99
> when -Infinity..25: 100
> when 123..Infinity: 200
> end
>
> --
> vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
>

Joel VanderWerf

8/14/2008 2:35:00 AM

elliottcable wrote:
> I always throw this in my core_ext:
>
>> class Float
>> Infinity = 1.0/0.0
>> end

If it goes in core it should really be

Infinity = 42/0.0

:)

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Todd Benson

8/14/2008 2:43:00 AM

On Wed, Aug 13, 2008 at 9:34 PM, Joel VanderWerf
<vjoel@path.berkeley.edu> wrote:
> elliottcable wrote:
>>
>> I always throw this in my core_ext:
>>
>>> class Float
>>> Infinity = 1.0/0.0
>>> end
>
> If it goes in core it should really be
>
> Infinity = 42/0.0
>
> :)

Infinity + Infinity
=> Infinity
Infinity - Infinity
=> NaN
Infinity + Infinity - Infinity
=> Nan

Todd

Todd

elliottcable

8/14/2008 2:44:00 AM

> Infinity =3D 42/0.0
> UniverseError: =E2=80=BD=E2=80=BD=E2=80=BD
> from (irb):2

On Aug 13, 2008, at 6:34 PM, Joel VanderWerf wrote:

> Infinity =3D 42/0.0

Joel VanderWerf

8/14/2008 3:53:00 AM

Todd Benson wrote:
> Infinity + Infinity
> => Infinity
> Infinity - Infinity
> => NaN
> Infinity + Infinity - Infinity
> => Nan

That seems right, or at least that's what I get counting on my fingers.

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

comp.lang.ruby

case statement and ranges

Mini Skirt

ara.t.howard

Ryan Davis

Todd Benson

Joel VanderWerf

elliottcable

Joel VanderWerf

Todd Benson

elliottcable

Joel VanderWerf

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