TIP #343: A BINARY SPECIFIER FOR [FORMAT/SCAN] 
================================================
 Version:      $Revision: 1.3 $
 Author:       Alexandre Ferrieux <alexandre.ferrieux_at_gmail.com>
 State:        Final
 Type:         Project
 Tcl-Version:  8.6
 Vote:         Done
 Created:      Wednesday, 03 December 2008
 URL:          https://tip.tcl-lang.org343.html
 Post-History: 

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 ABSTRACT 
==========

 This TIP proposes to add a %b specifier to the *format* and *scan* 
 commands for working with integers in base-2 representation. 

 BACKGROUND 
============

 The *format* and *scan* commands already have decimal, hexadecimal, and 
 octal support, but people wanting binary today resort to a hack, namely 
 going hexadecimal first and then *string map*ping the hex digits to 
 their four-bits binary representations. We also already have the "0b" 
 notation as input for *expr*. This lack is inelegant. 

 PROPOSED CHANGE 
=================

 This TIP proposes to reuse the existing binary representation machinery 
 to expose a new *%b* specifier: 

           format %b 5
           => 101
           scan 000101 %b x;set x
           => 5

 The good properties of the existing code make the addition really 
 painless, in that it automagically combines with the size (l,ll), width 
 (digits), and prefix (#) modifiers: 

           format %#06b 5
           => 0b0101
           format %llb [expr {(2**72-1)/7}]
           1001001001001001001001001001001001001001001001001001001001001001001001

 RATIONALE 
===========

 That is really low-hanging fruit. All the pieces are in place, it's 
 just a matter of exposition. The binary representation is a nice 
 pedagogic tool, and having it handy (rather than with a hack) is a 
 bonus. 

 REFERENCE IMPLEMENTATION 
==========================

 See Patch 2368084 
 [<URL:https://sourceforge.net/support/tracker.php?aid=2368084>]. 

 COPYRIGHT 
===========

 This document has been placed in the public domain. 

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