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Re: [Bug-apl] Make infinity and pi symbols into constants?

From: Elias Mårtenson
Subject: Re: [Bug-apl] Make infinity and pi symbols into constants?
Date: Thu, 16 Jan 2014 21:34:21 +0800

Point taken, and believe it or not, I actually mostly agree. :-)

That said, what is your opinion on making more characters legal as part of a symbol? This includes √ and ∞, but also the mathematical symbols things like 𝜓 (U+1D713) and ℝ (U+211D), just to name a couple.

Essentially, it'd be nice if the entire mathematical symbols pages was available.


On 16 January 2014 21:19, Juergen Sauermann <address@hidden> wrote:
Hi Elias,

I believe we should weight the advantages of such extensions against their disadvantages.

Obviously π is shorter than ○1 and √ is shorter than ⋆.5


- These symbols are on no APL keyboard,
- They are not in some APL fonts,
- They are rarely used.

Regarding ∞ right now GNU APL prints +∞ or -∞ if a number is larger than 1E307 or so. But you cannot enter
+∞ or -∞. They are output-only. It may make sense to use ¯∞ instead of -, but then  +∞ should become ∞
(otherwise +∞ and -∞ would use different formats. Not sure what looks better.

In the past, commercial APL vendors have used their extensions of APL in order to compete with other
commercial vendors. Which is fair enough. But it has also locked in the users of a particular interpreter
and then the "benefit" of a non-standard APL extension fires back. And, more importantly, the already
small community of APL users was divided into even smaller fractions that cannot easily exchange
their APL code.

Now, GNU APL is not commercial, so there is no need to compete by means of non-standard improvements of APL.

GNU APL also has its own extensions like ⎕INP and ⎕SI, but I would like to keep them at a minimum and stick to
the ISO standard as much as possible.

I have also seen things that have been implemented, which I consider simply awful and un-APL-ish.

Having all that said, I would like to hear more opinions about this topic. If there is a strong demand for the proposals
below, then I can implement them despite my concerns. My current plan with GNU APL is this:

GNU APL 1.3: Lambdas (aka. direct functions) and an open workspace interchange format
GNU APL 1.4: Parallel / multicore implementation of primitive functions and operators

/// Jürgen


I know some APL implementations (NARS2000 for example, if I remember correctly) allows you to use the symbol π as an alternative to ○1. Would it make sense to do the same for GNU APL?

Likewise, being able to type ∞ instead of ⌊/⍳0 would also be neat, mainly because it makes sense. Also, wouldn't it make sense to use ¯∞ as negative infinity, rather than -∞?

Oh, and one more extension would be to implement a function √ whose monadic form would return the square root, and dyadically returns the L root of R (this is something NARS does, I think).

If you don't think this makes sense, an alternative would be to simply allow these symbols as characters in names, and a program can define these functions and constants itself.


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