If == any item in an array

ruby-talk
1

I'd like to write something like

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]
case ext # determined from the photo file name
when PhotoEndings
<do something whenever ext is the same as any of the photo endings. >
when MovieEndings
<do something else>
else
end

I don't have to use case, any conditional will do.

Thanks. I hope I have explained this. I have no idea what to search for.
I did try some, but I'm a newbie and don't understand the more advanced
syntax.

I tried
when PhotoEndings.any
and
when PhotoEndings.or

Wild guesses, but they don't work.

···

--
Posted via http://www.ruby-forum.com/.

2

I think you're looking for Array#include?

$ ri Array#include?
--------------------------------------------------------- Array#include?
     array.include?(obj) -> true or false

···

On 6/20/07, 12 34 <rubyforum@web.knobby.ws> wrote:

I'd like to write something like

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]
case ext # determined from the photo file name
when PhotoEndings
<do something whenever ext is the same as any of the photo endings. >
when MovieEndings
<do something else>
else
end

I don't have to use case, any conditional will do.

------------------------------------------------------------------------
     Returns +true+ if the given object is present in _self_ (that is,
     if any object +==+ _anObject_), +false+ otherwise.

        a = [ "a", "b", "c" ]
        a.include?("b") #=> true
        a.include?("z") #=> false

Hope that helps,
-Harold

3

case
when PhotoEndings.include?(ext)
....
when MovieEndings.include?(ext)
...
end

The form
  case x
  when y
    #do something
  when z
     #do something else
  end
...

is actually equivalent to:

   if y === x
   then
      #do something
   elsif z === x
      # do something else
   end

and

   case #no value
   when y
       # do something
   when z
       # do something else
    end

   if y
   then
      #do something
   elsif z
      # do something else
   end

···

On 6/20/07, 12 34 <rubyforum@web.knobby.ws> wrote:

I'd like to write something like

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]
case ext # determined from the photo file name
when PhotoEndings
<do something whenever ext is the same as any of the photo endings. >
when MovieEndings
<do something else>
else
end

I don't have to use case, any conditional will do.

Thanks. I hope I have explained this. I have no idea what to search for.
I did try some, but I'm a newbie and don't understand the more advanced
syntax.

I tried
when PhotoEndings.any
and
when PhotoEndings.or

--
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

4

You could use regular expressions:

PhotoEndings = /JPG|MRW|JPE/i
MovieEndings = /AVI/i

case ext
when PhotoEndings
  <do something>
when MovieEndings
  <do something else>
else
  <do something else>
end

Regards,
Raf

···

2007/6/20, 12 34 <rubyforum@web.knobby.ws>:

I'd like to write something like

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]
case ext # determined from the photo file name
when PhotoEndings
<do something whenever ext is the same as any of the photo endings. >
when MovieEndings
<do something else>
else
end

I don't have to use case, any conditional will do.

Thanks. I hope I have explained this. I have no idea what to search for.
I did try some, but I'm a newbie and don't understand the more advanced
syntax.

I tried
when PhotoEndings.any
and
when PhotoEndings.or

Wild guesses, but they don't work.

--
Posted via http://www.ruby-forum.com/\.

5

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]

case ext # determined from the photo file name
when *PhotoEndings
   <do something whenever ext is the same as any of the photo endings. >
when *MovieEndings
   <do something else>
end

Cheers-

-- Ezra Zygmuntowicz -- Lead Rails Evangelist
-- ez@engineyard.com
-- Engine Yard, Serious Rails Hosting
-- (866) 518-YARD (9273)

···

On Jun 20, 2007, at 12:07 PM, 12 34 wrote:

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]
case ext # determined from the photo file name
when PhotoEndings
<do something whenever ext is the same as any of the photo endings. >
when MovieEndings
<do something else>
else
end

6

PhotoEndings = %w(JPG MRW JPE)
MovieEndings = %w(AVI)

case ext.upcase
when *PhotoEndings
  puts "I'm a photo!"
when *MovieEndings
  puts "I'm a movie!"
else
  puts "I'm unknown '#{ext}'"
end

When you were declaring your endings with the %w notation, you had put
commas between the file extensions. Therefore, your arrays only
contained one element.

Give this code a shot. You almost had it -- the syntax you were
looking for was the leading splat "*" in front of the PhotoEndings and
MovieEndings in the branches of the case statement.

Blessings,
TwP

···

On 6/20/07, 12 34 <rubyforum@web.knobby.ws> wrote:

I'd like to write something like

PhotoEndings = %w[JPG,MRW,JPE]
MovieEndings = %w[AVI]
case ext # determined from the photo file name
when PhotoEndings
<do something whenever ext is the same as any of the photo endings. >
when MovieEndings
<do something else>
else
end

I don't have to use case, any conditional will do.

Thanks. I hope I have explained this. I have no idea what to search for.
I did try some, but I'm a newbie and don't understand the more advanced
syntax.

7

Or take a completely different approach to the issue, use the mime/types
gem.

    require 'rubygems'
    require 'mime/types'

    # add in a non-standard mime type for MRW files
    mrw_mime_type = MIME::Type.from_array(['image/x-raw', %w[ mrw ]])
    MIME::Types.add(mrw_mime_type)

    test_files = %w[ jpeg_file.jpg jpeg_file.jpe mrw_file.mrw avi_file.avi mov_file.mov jkl_file.jkl ]

    test_files.each do |t|
        mime_types_for_t = MIME::Types.of(t)
       
        if mime_types_for_t.size > 0 then
            case mime_types_for_t.first.raw_media_type
            when "image"
                puts "#{t} is an image!"
            when "video"
                puts "#{t} is a video!"
            else
                puts "#{t} is a #{mt.raw_media_type}"
            end
        else
            puts "No mime types found for #{t}"
        end
    end

output:

    % ruby mrw-example.rb
    jpeg_file.jpg is an image!
    jpeg_file.jpe is an image!
    mrw_file.mrw is an image!
    avi_file.avi is a video!
    mov_file.mov is a video!
    No mime types found for jkl_file.jkl

enjoy,

-jeremy

···

On Thu, Jun 21, 2007 at 04:40:34AM +0900, Tim Pease wrote:

On 6/20/07, 12 34 <rubyforum@web.knobby.ws> wrote:
>I'd like to write something like
>
>PhotoEndings = %w[JPG,MRW,JPE]
>MovieEndings = %w[AVI]
>case ext # determined from the photo file name
>when PhotoEndings
><do something whenever ext is the same as any of the photo endings. >
>when MovieEndings
><do something else>
>else
>end
>
>I don't have to use case, any conditional will do.
>
>Thanks. I hope I have explained this. I have no idea what to search for.
>I did try some, but I'm a newbie and don't understand the more advanced
>syntax.
>

PhotoEndings = %w(JPG MRW JPE)
MovieEndings = %w(AVI)

case ext.upcase
when *PhotoEndings
puts "I'm a photo!"
when *MovieEndings
puts "I'm a movie!"
else
puts "I'm unknown '#{ext}'"
end

--

Jeremy Hinegardner jeremy@hinegardner.org

8

Tim Pease wrote:

PhotoEndings = %w(JPG MRW JPE)
MovieEndings = %w(AVI)

case ext.upcase
when *PhotoEndings
  puts "I'm a photo!"
when *MovieEndings
  puts "I'm a movie!"
else
  puts "I'm unknown '#{ext}'"
end

When you were declaring your endings with the %w notation, you had put
commas between the file extensions. Therefore, your arrays only
contained one element.

Give this code a shot. You almost had it -- the syntax you were
looking for was the leading splat "*" in front of the PhotoEndings and
MovieEndings in the branches of the case statement.

Blessings,
TwP

Thank you and all the others that answered. The array.include was what I
was thinking too. But removing a couple of commas and adding a couple of
astericks (splats) is nice. Ruby is great.

I don't understand the meaning of the *. I imagine it comes from the
wildcard usage. What do I look up in my books to understand this.

Again thanks to the great community. All the answers help me learn.

···

--
Posted via http://www.ruby-forum.com/\.

9

12 34 wrote:

Tim Pease wrote:

> PhotoEndings = %w(JPG MRW JPE)
> MovieEndings = %w(AVI)
>
> case ext.upcase
> when *PhotoEndings
> puts "I'm a photo!"
> when *MovieEndings
> puts "I'm a movie!"
> else
> puts "I'm unknown '#{ext}'"
> end

I don't understand the meaning of the *. I imagine it comes from the
wildcard usage. What do I look up in my books to understand this.

It has nothing to do with wildcards. The * takes an array and turns it into
a list of arguments. So args=[a,b,c]; f(*args) is the same as f(a,b,c) and
when *PhotoEndings is the same as when JPG, MRW, JPE

···

--
Ist so, weil ist so
Bleibt so, weil war so

10

When the splat-solution appeared here an alarm bell rung in my head:
If the array is small, like in this problem, everything is OK. But what
if the array is huge?

I was wondering whether stack overflows could occur. I havent found
them, but the benchmark shows that .include?() is faster.

require 'benchmark'
LIMIT = 10_000_000
STEP = LIMIT / 10 + 1
BIG_ARRAY = (1..LIMIT).to_a; nil

def look_by_splash(item)
  case item
  when *BIG_ARRAY
    'found by splash'
  else
    'not found by splash'
  end
end

def look_by_include(item)
  case
  when BIG_ARRAY.include?(item)
    'found by include'
  else
    'not found by include'
  end
end

Benchmark.bmbm do |x|
  x.report('by_splash') do
    1.step(LIMIT + STEP, STEP) { |i| look_by_splash(i) }
  end
  x.report('by_include') do
    1.step(LIMIT + STEP, STEP) { |i| look_by_include(i) }
  end
end

Rehearsal ---------------------------------------------
by_splash 13.080000 0.000000 13.080000 ( 13.212631)
by_include 6.750000 0.000000 6.750000 ( 6.817161)
----------------------------------- total: 19.830000sec

                user system total real
by_splash 12.930000 0.000000 12.930000 ( 13.060550)
by_include 6.750000 0.000000 6.750000 ( 6.809274)

I tested with LIMIT = 100_000_000, and the proportions are the same.

···

On 2007-06-21 09:17:24 +0900 (Thu, Jun), 12 34 wrote:

> Give this code a shot. You almost had it -- the syntax you were
> looking for was the leading splat "*" in front of the PhotoEndings and
> MovieEndings in the branches of the case statement.
>
Thank you and all the others that answered. The array.include was what I
was thinking too. But removing a couple of commas and adding a couple of
astericks (splats) is nice. Ruby is great.

I don't understand the meaning of the *. I imagine it comes from the
wildcard usage. What do I look up in my books to understand this.

--
Ceterum censeo Internet Explorer esse delendam.

11

If there are *many* choices you would probably choose another solution - namely creating a hash with file extensions as keys and lambdas as values that perform some operation.

Kind regards

  robert

···

On 21.06.2007 11:54, Mariusz Pękala wrote:

On 2007-06-21 09:17:24 +0900 (Thu, Jun), 12 34 wrote:

Give this code a shot. You almost had it -- the syntax you were
looking for was the leading splat "*" in front of the PhotoEndings and
MovieEndings in the branches of the case statement.

Thank you and all the others that answered. The array.include was what I was thinking too. But removing a couple of commas and adding a couple of astericks (splats) is nice. Ruby is great.

I don't understand the meaning of the *. I imagine it comes from the wildcard usage. What do I look up in my books to understand this.

When the splat-solution appeared here an alarm bell rung in my head:
If the array is small, like in this problem, everything is OK. But what
if the array is huge?

I was wondering whether stack overflows could occur. I havent found
them, but the benchmark shows that .include?() is faster.