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# Re: \ell

• To: MJD@MATH.AMS.ORG
• Subject: Re: \ell
• From: alanje@cogs.susx.ac.uk (Alan Jeffrey)
• Date: Thu, 5 Aug 93 15:20 BST
• CC: math-font-discuss@cogs.susx.ac.uk, mjd@MATH.AMS.ORG

>I don't understand the purpose of the \ell glyph from a
>mathematician's point of view. My conjecture: In ancient times
>mathematicians had to use typewriters where lowercase Latin l was
>indistinguishable from the numeral 1.

I agree with this conjecture, but I would also add that it's a
blackboard' glyph.  In the same way that open letters started being
used to simulate bold on the blackboard, \ell was used to distinguish
l' from 1'.

Unfortunately, since DEK included it in CM, it's become accepted as a
glyph in its own right (it's used as label' in Milner's (1989,
Prentice Hall) Communication And Concurrency, for example).

It would be nice to junk the thing, or insist that it's really the
lower case script l', but this means we're no longer upwardly
compatible.  So I'm afraid I'd have to go for solution 2.

A classic case of I wouldn't start from here, mate.'
There's a similar problem with v' and w' in that some fonts (such as
MathTime) provide a curly v' that can be distinguished from \nu',
and a curly w' to match the curly v'.  Should these be given
separate slots?  (I'd say no, on the grounds that the math italic
glyph shapes are often different from the text italic shapes, c.f.
cmmi a' and cmti a'.)

Alan.



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