rfc:logicalshiftoperator

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rfc:logicalshiftoperator [2011/07/18 00:24] – Add note about <<< being used by heredoc ircmaxellrfc:logicalshiftoperator [2014/04/08 22:47] – Inactive levim
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 ====== Request for Comments: Add a Logical Shift Operator For Strings ====== ====== Request for Comments: Add a Logical Shift Operator For Strings ======
   * Version: 1.0   * Version: 1.0
-  * Date: 2008-03-06+  * Date: 2011-17-07
   * Author: Anthony Ferrara <ircmaxell@php.net>   * Author: Anthony Ferrara <ircmaxell@php.net>
-  * Status: Under Discussion+  * Status: Inactive
   * First Published at: http://wiki.php.net/rfc/logicalshiftoperator   * First Published at: http://wiki.php.net/rfc/logicalshiftoperator
  
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 The currently implemented left and right shift operators (''<<'' and ''>>'' respectively) perform [[http://en.wikipedia.org/wiki/Bitwise_operation#Arithmetic_shift|arithmetic shifts]].  I am proposing the introduction of a pair of [[http://en.wikipedia.org/wiki/Logical_shift|logical shift]] operators which perform their operations on arbitrary length strings. The currently implemented left and right shift operators (''<<'' and ''>>'' respectively) perform [[http://en.wikipedia.org/wiki/Bitwise_operation#Arithmetic_shift|arithmetic shifts]].  I am proposing the introduction of a pair of [[http://en.wikipedia.org/wiki/Logical_shift|logical shift]] operators which perform their operations on arbitrary length strings.
  
-The problem can be seen by trying to shift ''-1'' (''0xFFFFFFFF'' on 32 bit, ''0xFFFFFFFFFFFFFFFF'' on 64 bit).  If we try ''-1 >> 1'', we get back ''-1'' again.  This is due to the shift being arithmetic.  If we try ''-1 >> 2'', we will still get ''-1''.  +The problem can be seen by trying to shift ''-1'' (''0xFFFFFFFF'' on 32 bit, ''0xFFFFFFFFFFFFFFFF'' on 64 bit).  If we try ''-1 %%>>%% 1'', we get back ''-1'' again.  This is due to the shift being arithmetic.  If we try ''-1 %%>>%% 2'', we will still get ''-1''.  
  
-Additionally, the current shifts only work on strings when the string is parsable as a number.  So ''"2" >> 1'' yields ''1'' instead of the expected logical value of ''0x19''.+Additionally, the current shifts only work on strings when the string is parsable as a number.  So ''"2" %%>>%% 1'' yields ''1'' instead of the expected logical value of ''0x19''.
  
 At present, if you want to do a logical shift on a string, you need to iterate over the string and apply the shift to each part of it (where the part is less than 4 bytes long, to prevent issues on 32 bit systems).  For example: At present, if you want to do a logical shift on a string, you need to iterate over the string and apply the shift to each part of it (where the part is less than 4 bytes long, to prevent issues on 32 bit systems).  For example:
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 ===== Proposal ===== ===== Proposal =====
  
-I propose the addition of two new operators which will perform a logical shift.  The selection of the operators is a little bit more difficult as ''<<<'' is already taken by heredoc.  Perhaps something like ''b<<''...+I propose the addition of two new operators which will perform a logical shift.  The selection of the operators is a little bit more difficult as ''%%<<<%%'' is already taken by heredoc.  Perhaps something like ''b%%<<%%''...
  
 Example: Example:
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 ===== Changelog ===== ===== Changelog =====
  
- - Added note about <<< being used by heredoc already.+ - Added note about %%<<<%% being used by heredoc already.
  
rfc/logicalshiftoperator.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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