From: Emanuel Berg via help-gnu-emacs <help-gnu-emacs@gnu.org>
To: help-gnu-emacs@gnu.org
Cc: Ingemar Holmgren <dag.h@hotmail.se>
Subject: Re: Calculator: no exponent, full number ?
Date: Thu, 06 Jun 2019 01:47:37 +0200 [thread overview]
Message-ID: <86tvd3sig6.fsf@zoho.eu> (raw)
In-Reply-To: 20190605095317.499f2082@mistral
jonetsu wrote:
> Emmanuel Berg: "Or use Lisp, create a file
> and just type Lisp. With `format', you can
> get the result look anyway you want."
>
> I must say that I do not know anything about
> Lisp [...]
If you want to do math with Lisp, it is much
better to be good with math and bad at Lisp,
than the other way around.
Because it is very easy. Just understand the
"fully parenthesized prefix notation" [1] and
that will be it.
So, the operator comes first:
(+ 1 2 3 4) ; is 1 + 2 + 3 + 4 = 10
And, the priority of operators is never an
issue as _everything_ is parenthesized.
That's it!
For more advanced math, you'll probably need to
find a math library with additional operators
and constants, perhaps in on of the
[M]ELPA packs, but for the basic stuff, it is
as simple as it can be.
Here, have a look:
(defun hypotenuse (c1 c2)
(sqrt (+ (* c1 c1) (* c2 c2))) )
or, a little bit more advanced, involving
a list and a set function:
(defun mean-value (vs)
(let*((sum (apply #'+ vs))
(mean (/ sum (length vs) 1.0)) )
mean) ) ; [2]
Eval me: (mean-value '(1 2 3 4 5.5)) ; 3.1
One of the advantages with this Lisp-file
method is that you have every data item in the
file. Nothing gets lost in the history of the
calculator, and what you have you can change
and instantly have the whole thing
computed anew.
[1] https://en.wikipedia.org/wiki/Lisp_(programming_language)
[2] https://dataswamp.org/~incal/emacs-init/my-math.el
--
underground experts united
http://user.it.uu.se/~embe8573
https://dataswamp.org/~incal
next prev parent reply other threads:[~2019-06-05 23:47 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-04 19:43 Calculator: no exponent, full number ? jonetsu
2019-06-04 22:42 ` Emanuel Berg via help-gnu-emacs
2019-06-05 11:15 ` Emanuel Berg via help-gnu-emacs
2019-06-05 4:11 ` Marcin Borkowski
2019-06-05 4:26 ` Emanuel Berg via help-gnu-emacs
2019-06-05 13:53 ` jonetsu
2019-06-05 23:47 ` Emanuel Berg via help-gnu-emacs [this message]
2019-06-06 14:50 ` Nick Dokos
2019-06-26 4:09 ` Xavier Maillard
2019-06-06 15:47 ` Marcin Borkowski
2019-06-06 16:50 ` Emanuel Berg via help-gnu-emacs
2019-06-06 17:04 ` tomas
2019-06-06 17:11 ` Emanuel Berg via help-gnu-emacs
2019-06-06 17:25 ` tomas
2019-06-07 19:36 ` Marcin Borkowski
2019-06-14 12:20 ` Van L
2019-06-14 13:26 ` Robert Pluim
2019-06-14 19:57 ` Stefan Monnier
2019-06-15 9:29 ` Van L
2019-06-14 19:43 ` Emanuel Berg via help-gnu-emacs
2019-06-15 9:23 ` Van L
-- strict thread matches above, loose matches on Subject: below --
2019-06-06 17:28 Joe Trivers via help-gnu-emacs
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