From: Robert Klemme <shortcutter@...>
Date: 2008-03-12T06:45:27+09:00
Subject: Re: duplicating characters in a string

On 11.03.2008 19:53, William James wrote:

Btw, is there any particular reason why you duplicated the mail content?

> On Mar 11, 9:26 am, Robert Klemme <shortcut...@googlemail.com> wrote:
>> 2008/3/11, William James <w_a_x_...@yahoo.com>:
>>
>>> On Mar 7, 11:45 pm, Joel VanderWerf <vj...@path.berkeley.edu> wrote:
>>>  > Rehearsal ---------------------------------------------------
>>>  > s.gsub(re){...}   6.220000   0.010000   6.230000 (  6.325230)
>>>  > s.gsub(re,...)    3.020000   0.060000   3.080000 (  3.115286)
>>>  > 7stud             4.110000   0.000000   4.110000 (  4.142912)
>>>  > 7stud             2.050000   0.000000   2.050000 (  2.072398)
>>>  > ----------------------------------------- total: 15.470000sec
>>>  >                        user     system      total        real
>>>  > s.gsub(re){...}   5.910000   0.020000   5.930000 (  5.993456)
>>>  > s.gsub(re,...)    3.000000   0.000000   3.000000 (  3.017119)
>>>  > 7stud             4.100000   0.020000   4.120000 (  4.300772)
>>>  > 7stud             2.030000   0.010000   2.040000 (  2.068190)
>>> Pascal (FreePascal):
>>>  uses sysutils;  // for timing
>>>  function dup_chars( s: ansistring ): ansistring;
>>>  var
>>>   out: ansistring;
>>>   i,j: longint;
>>>   c: char;
>>>  begin
>>>   setlength( out, length(s) * 2 );
>>>   for i := 1 to length(s) do
>>>   begin
>>>     c := s[i];   j := (i shl 1);
>>>     out[j-1] := c;
>>>     out[j] := c;
>>>   end;
>>>   exit( out )
>>>  end;
>>>  var
>>>   s : ansistring;
>>>   i : longint;
>>>   when : tDateTime;
>>>  begin
>>>   s := '';
>>>   for i:=1 to 1000000 do  s += 'abc';
>>>   when := Time;
>>>   dup_chars( s );
>>>   writeln( ((time - when) * secsPerDay):0:3, ' seconds' )
>>>  end.
>>>   --->0.031 seconds
>> Your point being?
>>
>> robert
>>
>> --
>> use.inject do |as, often| as.you_can - without end
> 
> On my computer:
> 
> s.gsub(re, ...)  --> 9.641000 seconds
> Lua              --> 1.078   seconds
> 
> Ruby's gsub is far too slow.  7stud even beat it with an each_byte
> loop!
> Disgraceful.  Disgusting.  Inexcusable.
> 
> The Lua code:
> 
> s = string.rep( 'abc', 1000000 )
> 
> time = os.clock()
> string.gsub( s, '(.)', "%1%1" )
> print( os.clock() - time, "seconds" )

I do not know Lua.  Does this return a copied string or does it do it 
inplace?

Kind regards

	robert