# Re: Solidus variations

From: Hans Aberg <haberg-1_at_telia.com>
Date: Fri, 7 Oct 2011 23:13:12 +0200

On 7 Oct 2011, at 22:29, Asmus Freytag wrote:

> Murray's work comes from the desire to represent mathematical equations faithfully, based nearly entirely on the semantics of the operators and having those operators be represented as Unicode characters.
>
> One solution that he uses is the use of "redundant" parens. Parens can be supplied to group operands, so that you get the correct precedence, but, where they are not necessary to the human reader, they will be dropped in the formatted equation.
>
> As input format, the linear format, therefore looks more like current source code, in that one does type parens.
>
> When fractions are built up, you don't need the parens, so they are dropped in layout. If you take the same fraction and display it inline (with a slash) some or all of the parens would be needed for the human reader as well, so those are displayed.
>
> How would you parse 5.5 if input as a fraction? 51/2? You do need some form of grouping to recognize that the 5 and the 1 are not part of the same numerator.

Apart from that I treat as 5.5 as an inexact number, distinct from the exact rational numbers, I use right now "5 1/2", requiring there to be exactly one space, where the "/" can also be a ⁄ U+2044 FRACTION SLASH.

Expressions like "f x" parse as function application "f(x)", which is popular now in functional languages such as Haskell. So in principle, "5 1/2" might parse as "5(1/2)", the constant function 5 applied to 1/2.

Hans
Received on Fri Oct 07 2011 - 16:17:09 CDT

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