Substring like in PHP's substr()?

ruby-talk
1

Hi all

I'm looking for the coolest way to get the substring

/Webwork/pgbookings

out of

/Users/Josh/Webwork/pgbookings

The part /Users/Josh is saved in the variable my_var.

In PHP I would do something like the following:

substr(/Users/Josh/Webwork/pgbookings, strlen(my_var)) # =>
/Webwork/pgbookings

What's the fastest way to do this in Ruby? :slight_smile:
Josh

···

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2

I'm not sure which way is faster, so let's ask Ruby to time some of my ideas:

#!/usr/bin/env ruby -w

require "benchmark"

data = "/Users/Josh/Webwork/pgbookings"
prefix = "/Webwork/pgbookings"

TESTS = 1_000_000
Benchmark.bmbm do |results|
   results.report("[i..-i]:") { TESTS.times { data[prefix.length..-1] } }
   results.report("[i, l]:") { TESTS.times { data[prefix.length, data.length] } }
   results.report("sub():") { TESTS.times { data.sub(/\A#{prefix}/, "") } }
   results.report("[re, c]:") { TESTS.times { data[/\A#{prefix}(.+)/, 1] } }
end
# >> Rehearsal --------------------------------------------
# >> [i..-i]: 2.500000 0.000000 2.500000 ( 2.511868)
# >> [i, l]: 0.630000 0.000000 0.630000 ( 0.634460)
# >> sub(): 6.800000 0.020000 6.820000 ( 6.850561)
# >> [re, c]: 7.180000 0.010000 7.190000 ( 7.204910)
# >> ---------------------------------- total: 17.140000sec
# >>
# >> user system total real
# >> [i..-i]: 2.500000 0.000000 2.500000 ( 2.500795)
# >> [i, l]: 0.630000 0.010000 0.640000 ( 0.633458)
# >> sub(): 6.840000 0.000000 6.840000 ( 6.853133)
# >> [re, c]: 7.110000 0.010000 7.120000 ( 7.130398)

__END__

Hope that helps.

James Edward Gray II

···

On Apr 9, 2007, at 6:52 AM, Joshua Muheim wrote:

Hi all

I'm looking for the coolest way to get the substring

/Webwork/pgbookings

out of

/Users/Josh/Webwork/pgbookings

The part /Users/Josh is saved in the variable my_var.

In PHP I would do something like the following:

substr(/Users/Josh/Webwork/pgbookings, strlen(my_var)) # =>
/Webwork/pgbookings

What's the fastest way to do this in Ruby? :slight_smile:

3

James Gray wrote:

···

On Apr 9, 2007, at 6:52 AM, Joshua Muheim wrote:

Looks COOL... :smiley:

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4

data = "/Users/Josh/Webwork/pgbookings"
prefix = "/Webwork/pgbookings"

I think you meant
   prefix = "/Users/Josh"

This doesn't affect the qualitative results of the benchmark but it
does change it to do what the OP was trying to do.

Note that "/Webwork/pgbookings" is NOT a prefix of
"/Users/Josh/Webwork/pgbookings"

And cosmetically there's a typo:

   results.report("[i..-i]:") { TESTS.times { data
[prefix.length..-1] } }

should be:

   results.report("[i..-1:") { TESTS.times { data[prefix.length..-1] } }

···

On 4/9/07, James Edward Gray II <james@grayproductions.net> wrote:

--
Rick DeNatale

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

5

data = "/Users/Josh/Webwork/pgbookings"
prefix = "/Webwork/pgbookings"

I think you meant
  prefix = "/Users/Josh"

This doesn't affect the qualitative results of the benchmark but it
does change it to do what the OP was trying to do.

Oops, I did. Thank you.

And cosmetically there's a typo:

   results.report("[i..-i]:") { TESTS.times { data
[prefix.length..-1] } }

should be:

  results.report("[i..-1:") { TESTS.times { data[prefix.length..-1] } }

Yeah, I blew that one, didn't I?

Thanks for the corrections.

James Edward Gray II

···

On Apr 9, 2007, at 8:33 AM, Rick DeNatale wrote:

On 4/9/07, James Edward Gray II <james@grayproductions.net> wrote:

6

Thank you guys. :slight_smile:

···

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