For loop

Ruby
1

Consider the following for loop in ‘C’ or ‘c++’ or ‘java’

      for (i=namespaceEnd - 1; i >= 0; i--)

Please help me with code to do the same functionality in ruby

2

Martin D. [email protected] writes:

Consider the following for loop in ‘C’ or ‘c++’ or ‘java’

      for (i=namespaceEnd - 1; i >= 0; i--)

Please help me with code to do the same functionality in ruby

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

How about this:

(namespace_end - 1).downto(0) { |x| puts x }

Hope that helps,
Carl.

3

Thank you carl, iam very new to this language

sorry carl could you help with this code fully

for( int i = namespaceEnd -1; i >= 0; i–) {
if( prefix.equals( namespacePrefix[ i ] ) ) {
return namespaceUri[ i ];
}

thank you in advance

4

Martin D. wrote:

Consider the following for loop in ‘C’ or ‘c++’ or ‘java’

      for (i=namespaceEnd - 1; i >= 0; i--)

Please help me with code to do the same functionality in ruby

ruby does not really have a for loop as such but there are various ways
to get the job done. You saw the upto approach. Here is another:

namespaceEnd.times do

your code in here

end

now, this works for 0…namespace - 1 automatically. If you need to run
in reverse, can use the downto or a calculation.

namespaceEnd.times do |my_var|
some_array[namespaceEnd - my_var] = some_val
end

but that is clunky. If you are iterating through an array you can use
the each loop:

my_arr = [“aaa”, “bbb”, “ccc”, “ddd”]
my_arr.each_with_index {|str, idx| puts “#{idx}. #{str}”}

=>
0. aaa

  1. bbb
  2. ccc
  3. ddd

If you want only the values, use my_arr.each
If you want only the index position, use my_arr.each_index

HTH

5

Martin D. wrote:

Thank you carl, iam very new to this language

sorry carl could you help with this code fully

for( int i = namespaceEnd -1; i >= 0; i–) {
if( prefix.equals( namespacePrefix[ i ] ) ) {
return namespaceUri[ i ];
}

thank you in advance

(namespace_end - 1).downto(0) { |x|
return namespaceUri[x] if prefix==namespacePrefix[x] }

Todd

6

Martin D. [email protected] writes:

thank you in advance

I suspect you’re looking for the element in the namespaceUri
array which is at the position determined by looking up the
position of ‘prefix’ in the namespacePrefix array (how very
unsettling). Assuming namespaceEnd is actually the count of
elements in the namespacePrefix array, would this work?

your_value = (i = namespace_prefix.index(prefix)) ?
namespace_uri[i] :
nil

Where ‘your_value’ will now contain the namespace_uri value,
or nil if it was not found in namespace_prefix

If i’ve misunderstood your question, post back with the values
of prefix, namespacePrefix, namespaceUri and namespaceEnd, and
what you expect to get out of it and I’ll see if I can’t help.

7

Todd B. [email protected] writes:

thank you in advance

(namespace_end - 1).downto(0) { |x|
return namespaceUri[x] if prefix==namespacePrefix[x] }

Todd

I’m getting a ‘LocalJumpError: unexpected return’ error when
I try to return from within a downto block, is this supported
in your version?

Carl.

8

On Wed, 21 Nov 2007 13:39:58 +0900, Martin D.
[email protected]
wrote:

thank you in advance

You might consider using an array of namespace objects instead of
parallel
arrays

class Namespace
attr_reader :prefix, :uri
def initialize(prefix, uri)
@prefix = prefix
@uri = uri
end
end

namespaces = [ Namespace.new(“prefix”, “uri”), …]

then your code becomes something like:

matching_namespace = namespaces.find {|namespace| namespace.prefix ==
prefix)
return matching_namespace ? matching_namespace.uri : nil

9

Paul McMahon [email protected] writes:

end

namespaces = [ Namespace.new(“prefix”, “uri”), …]

then your code becomes something like:

matching_namespace = namespaces.find {|namespace| namespace.prefix ==
prefix)
return matching_namespace ? matching_namespace.uri : nil

Good point.
I suspect in this case a plain old Hash might do wonders to simplify
the problem…

Carl.

10

On 21.11.2007 04:59, Martin D. wrote:

Consider the following for loop in ‘C’ or ‘c++’ or ‘java’

      for (i=namespaceEnd - 1; i >= 0; i--)

Please help me with code to do the same functionality in ruby

Did you actually read a tutorial or book about the language? If not,
it’s probably easier to do that vs. trying to cover all these basic
questions via newsgroup…

Cheers

robert

11

Sorry the code is running well in my system. I didnt got any error. I
have checked the code with my applications.

12

“Martin D.” [email protected] wrote in message
news:[email protected]…

Consider the following for loop in ‘C’ or ‘c++’ or ‘java’

     for (i=namespaceEnd - 1; i >= 0; i--)

Please help me with code to do the same functionality in ruby

I'm surprised no one's suggested the obvious:

namespace.reverse_each do |i|
# Do something with i
end

...this assumes you don't actually need an index, which is usually

the
case. It also assumes that namespaceEnd is the end of a container
called
“namespace,” or some such…

If you need the index, instead of the array, you'll have to do

something
wild and zany, like:

namespace.reverse.each_index do |i|
# Do something with i
end

...does this help?