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comp.lang.ruby

Array index of first bigger number...

Josselin

6/2/2007 7:31:00 AM

Is there a simple function (I solve it w a loop.. C-minded) to find the
index of the first bigger element in an array

limit mini is first_element , if item < last_element
item = -2.23
anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
0.0 index 0

item = 2.85
anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
5.0 index 2

item = 12.55
anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
15.0 index 4

limit maxi is last_element , if item > last_element
item = 36.59
anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
25.0 index 5

can it be writtent in just one line or a loop is unavoidable ?

thanks

joss
3 Answers

Stefano Crocco

6/2/2007 7:54:00 AM

0

Alle sabato 2 giugno 2007, Josselin ha scritto:
> Is there a simple function (I solve it w a loop.. C-minded) to find the
> index of the first bigger element in an array
>
> limit mini is first_element , if item < last_element
> item = -2.23
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 0.0 index 0
>
> item = 2.85
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 5.0 index 2
>
> item = 12.55
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 15.0 index 4
>
> limit maxi is last_element , if item > last_element
> item = 36.59
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 25.0 index 5
>
> can it be writtent in just one line or a loop is unavoidable ?
>
> thanks
>
> joss

You can do:

anArray.index(anArray.find{|i| i > item})

anArray.find will return the first element of the array for which the block
returns true, i.e the first element which is greater than item; then
anArray.index will return the index of the item. (This returns nil if no
element in the array is greater than item)

I hope this helps

Stefano

Robert Klemme

6/2/2007 8:59:00 AM

0

On 02.06.2007 09:30, Josselin wrote:
> Is there a simple function (I solve it w a loop.. C-minded) to find the
> index of the first bigger element in an array
>
> limit mini is first_element , if item < last_element
> item = -2.23
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 0.0 index 0
>
> item = 2.85
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 5.0 index 2
>
> item = 12.55
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 15.0 index 4
>
> limit maxi is last_element , if item > last_element
> item = 36.59
> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
> 25.0 index 5
>
> can it be writtent in just one line or a loop is unavoidable ?

Yes, it can. Just use Enumerator.

irb(main):001:0> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0]
=> [0.0, 2.0, 5.0, 10.0, 15.0, 25.0]

irb(main):007:0> anArray.to_enum(:each_with_index).find {|n,i| n > 30}
=> nil
irb(main):008:0> anArray.to_enum(:each_with_index).find {|n,i| n > 10}
=> [15.0, 4]
irb(main):009:0> anArray.to_enum(:each_with_index).find {|n,i| n > -2.23}
=> [0.0, 0]
irb(main):010:0> val, idx = anArray.to_enum(:each_with_index).find
{|n,i| n > -2.23}
=> [0.0, 0]
irb(main):011:0> val
=> 0.0
irb(main):012:0> idx
=> 0

This also has the advantage of having to traverse the array just once
vs. the solution Stefano presented.

Kind regards

robert

Josselin

6/2/2007 9:24:00 AM

0

On 2007-06-02 10:59:03 +0200, Robert Klemme <shortcutter@googlemail.com> said:

> On 02.06.2007 09:30, Josselin wrote:
>> Is there a simple function (I solve it w a loop.. C-minded) to find the
>> index of the first bigger element in an array
>>
>> limit mini is first_element , if item < last_element
>> item = -2.23
>> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
>> 0.0 index 0
>>
>> item = 2.85
>> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
>> 5.0 index 2
>>
>> item = 12.55
>> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
>> 15.0 index 4
>>
>> limit maxi is last_element , if item > last_element
>> item = 36.59
>> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0] first_bigger_element =
>> 25.0 index 5
>>
>> can it be writtent in just one line or a loop is unavoidable ?
>
> Yes, it can. Just use Enumerator.
>
> irb(main):001:0> anArray = [0.0, 2.0, 5.0, 10.0, 15.0, 25.0]
> => [0.0, 2.0, 5.0, 10.0, 15.0, 25.0]
>
> irb(main):007:0> anArray.to_enum(:each_with_index).find {|n,i| n > 30}
> => nil
> irb(main):008:0> anArray.to_enum(:each_with_index).find {|n,i| n > 10}
> => [15.0, 4]
> irb(main):009:0> anArray.to_enum(:each_with_index).find {|n,i| n > -2.23}
> => [0.0, 0]
> irb(main):010:0> val, idx = anArray.to_enum(:each_with_index).find
> {|n,i| n > -2.23}
> => [0.0, 0]
> irb(main):011:0> val
> => 0.0
> irb(main):012:0> idx
> => 0
>
> This also has the advantage of having to traverse the array just once
> vs. the solution Stefano presented.
>
> Kind regards
>
> robert

thanks, Robert
that's what I was trying to avoid... I was close to Stefano's solution