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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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