84 lines
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84 lines
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<H2>Issue FORMAT-ATSIGN-COLON Writeup</H2>
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<PRE><B>Issue:</B> <A HREF="iss164.htm">FORMAT-ATSIGN-COLON</A><P>
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<B>References:</B> <A REL=DEFINITION HREF="../Body/f_format.htm#format"><B>FORMAT</B></A> description (p386)<P>
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<B>Category:</B> CLARIFICATION<P>
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<B>Edit history:</B> Version 1 by Pitman 02/27/87<P>
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Version 2 by cleanup committee 15-Mar-87<P>
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Version 3 by Masinter 15-Mar-87<P>
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Version 4 by Masinter 5-Jun-87<P>
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<P>
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<B>Problem Description:<P>
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</B><P>
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CLtL describes the format op syntax as:<P>
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<P>
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"a format directive consists of a tilde (~), optional prefix parameters<P>
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separated by commas, optional colon (:) and atsign (@) modifiers, and a<P>
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single character indicating what kind of directive this is."<P>
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<P>
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CLtL uses :@ fairly consistently throughout without saying whether @: is<P>
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legal. Is @: allowed?<P>
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<P>
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<B>Proposal (FORMAT-ATSIGN-COLON:OK):<P>
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</B><P>
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There is no required ordering between the @ and : modifier.<P>
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<P>
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<B>Rationale:<P>
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</B><P>
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This is currently underspecified, and this way of specifying it will<P>
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cause the least disruption to user code.<P>
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<P>
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<B>Current practice:<P>
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</B><P>
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Most implementations accept these in either order. Some implementations<P>
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have been known to expect only :@.<P>
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<P>
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<B>Adoption Cost:<P>
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</B><P>
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The change to accept either syntax is probably quite trivial.<P>
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<P>
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<B>Benefits:<P>
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</B><P>
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Having @: and :@ mean different things would be awkward. <P>
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<P>
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<B>Conversion Cost:<P>
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</B><P>
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Existing user code would be unaffected.<P>
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<P>
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<B>Aesthetics:<P>
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</B><P>
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Leaving these unordered is slightly simpler conceptually.<P>
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<P>
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<B>Discussion:<P>
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</B><P>
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The cleanup committee supports this clarification.<P>
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<P>
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</PRE>
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