Re: pi seems not to be a constant

 > PI is required to be the best long float approximation to pi. If it
 > wasn't then it would be wrong.

But that is already long unless long float digits is at its maximal
value.

 > Also, PI is required to be a constant variable. It isn't and so it's
 > wrong.  But i  think this "wrong" is a very small price to pay in
 > exchange for having adjustable precision long floats.

I'm not proposing to keep LONG-FLOAT-DIGITS at its maximal value,
so I'm satisfied allowing PI not to be the best available approximation.

 > In this case you are using a Clisp extension and you are getting what
 > Clisp promises to deliver. So it is right.

Setting LONG-FLOAT-DIGITS is also using a clisp extension.
By using that you accept whatever non-conformance it causes.

 > The problem then is the value of CL:PI.  What do you propose it should be?

I propose it should be the default value before changing
LONG-FLOAT-DIGITS. 

 > If you use EXT:LONG-FLOAT-DIGITS then you are outside of portable CL,
 > and you should take into account your uses of this function in your
 > coding.
Exactly.  So PI should be the constant value that it would be without
using that.

 > If you don't use EXT:LONG-FLOAT-DIGITS then the only non-confomance is
 > that some things that should be constant variables are variables
 > instead (but they won't in fact vary).

In my solution, if you don't use long-float-digits one might
reasonably argue that everything is compliant - there are no better
approximations of pi available without using long-float-digits.

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