[Edu-sig] Re: rationals

[Dennis E. Hamilton]

I know this isn't the place for this, but the conversation is a lot of fun.

If I were creating a canonical form for input-output, it would be based
around

<simple-rational> ::= <simple-non-rational-numeral>R |
<simple-non-rational-numeral>r

<rational-numeral> ::= <simple-rational> | <simple-rational> /
<simple-non-rational-numeral>

where the "/..." part is optional and one might even relax the denominator
<simple-non-rational-numeral> constraint in an input stream.

Note that 1.5e-3r/17

would be a valid input, but the canonical output of its value is more likely
to be "3r/34000".

In expressions, the "/" would just be a "/" and everything works as expected
for "/".

-- orcmid

------------------
Dennis E. Hamilton
http://NuovoDoc.com/
mailto:dennis.hamilton@acm.org
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-----Original Message-----
From: edu-sig-admin@python.org [mailto:edu-sig-admin@python.org]On
Behalf Of Kirby Urner
Sent: Friday, October 11, 2002 11:24
To: Christopher A. Craig
Cc: edu-sig@python.org
Subject: Re: [Edu-sig] Re: rationals


[ ... ]

I like J's economy, but I can see 1/2r as a very viable alternative.
As you say, it has much in common with 1+2j, where you need both
+ and j (two symbols) to signify complex.

An argument for 1r2 is that 1e2 sets a precedent.  But 1j2 is not
legal in Python, as it is in J, so the consistency is shakier
(not as *much* precedent).

Another point:

With longs, I can use either upper or lower case l, which isn't
so readable in code, as lowercase l looks like 1.  But r and R
are clearly not numbers.  So I assume the following would likewise
be legal:

     >>> 1/2R
  (1/2)r

or maybe that's 1/2r -- not sure which.

Kirby




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