CLHS: Issue FORMAT-ATSIGN-COLON Writeup

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## Issue FORMAT-ATSIGN-COLON Writeup

    Issue:        FORMAT-ATSIGN-COLON
    References:   FORMAT description (p386)
    Category:     CLARIFICATION
    Edit history: Version 1 by Pitman 02/27/87
                  Version 2 by cleanup committee 15-Mar-87
                  Version 3 by Masinter 15-Mar-87
    	      Version 4 by Masinter  5-Jun-87

    Problem Description:

    CLtL describes the format op syntax as:

    "a format directive consists of a tilde (~), optional prefix parameters
    separated by commas, optional colon (:) and atsign (@) modifiers, and a
    single character indicating what kind of directive this is."

    CLtL uses :@ fairly consistently throughout without saying whether @: is
    legal. Is @: allowed?

    Proposal (FORMAT-ATSIGN-COLON:OK):

    There is no required ordering between the @ and : modifier.

    Rationale:

    This is currently underspecified, and this way of specifying it will
    cause the least disruption to user code.

    Current practice:

    Most implementations accept these in either order. Some implementations
    have been known to expect only :@.

    Adoption Cost:

    The change to accept either syntax is probably quite trivial.

    Benefits:

    Having @: and :@ mean different things would be awkward.

    Conversion Cost:

    Existing user code would be unaffected.

    Aesthetics:

    Leaving these unordered is slightly simpler conceptually.

    Discussion:

    The cleanup committee supports this clarification.

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