Issue SYMBOL-PRINT-ESCAPE-BEHAVIOR Writeup

Issue:        SYMBOL-PRINT-ESCAPE-BEHAVIOR

Forum:        X3J13 Letter Ballot

References:   *PRINT-ESCAPE* (X3J13/92-102, p22-4)

	      Public review comment Moon-1

	      Public review comment Loosemore-17

	      Public review comment Pitman-9

Category:     CLARIFICATION

Edit history: 21-Jun-93, Version 1 by Steele (based on text by Loosemore)

Status:		Proposal CLARIFY passed 10-1 on letter ballot 93-304.


Problem Description:


  The description of how symbols are printed when *PRINT-ESCAPE* is

  true is too vague.  Three PR commentors remarked on this.


Proposal (SYMBOL-PRINT-ESCAPE-BEHAVIOR:CLARIFY):


  Replace the text:


    \term{Backslashes} and \term{vertical-bars} are included as required.  

    The \term{current output base} at the time of printing might be relevant.

    For example, if \thevalueof{*print-base*} were \f{16} 

    when printing the symbol \f{face}, it would have to be printed as

    \f{\\FACE} or \f{\\Face} or \f{|FACE|}, 

    because the token \f{face} would be read as a hexadecimal

    number (decimal value 64206) if \thevalueof{*read-base*} were \f{16}.


  with:


    When printing a \term{symbol}, the printer inserts enough 

    \term{single escape} and/or \term{multiple escape}

    characters (\term{backslashes} and/or \term{vertical-bars}) so that if

    \funref{read} were called with the same \varref{*readtable*} and

    with \varref{*read-base*} bound to the \term{current output base}, it

    would return the same \term{symbol} (if it is not 

    \term{apparently uninterned}) or an \term{uninterned} \term{symbol}

    with the same \term{print name} (otherwise).


    For example, if \thevalueof{*print-base*} were \f{16} 

    when printing the symbol \f{face}, it would have to be printed as

    \f{\\FACE} or \f{\\Face} or \f{|FACE|}, 

    because the token \f{face} would be read as a hexadecimal

    number (decimal value 64206) if \thevalueof{*read-base*} were \f{16}.


    See \varref{*print-readably*} for additional restrictions concerning

    characters with  nonstandard \term{syntax types} in the 

    \term{current readtable}.

  

Test Case:


  Not provided.


Rationale:


  Explain more fully what is meant by "as required".


Current Practice:


  Not provided.


Cost to Implementors:


  Probably relatively small.


Cost to Users:


  None.  This change doesn't affect anything already guaranteed to the user.


Cost of Non-Adoption:


  Vagueness in the language specification.


Benefits:


  Better program portability.


Editorial Impact:


  Small.  A small, localized edit.


Aesthetics:


  Mostly neutral.


Discussion:

  

  This addresses comments Moon #1, Loosemore #17, and Pitman #9.