On Fri, 12 Dec 2003 15:32:09 -0800 (PST)
Robert Dodier <robert_dodier@yahoo.com> wrote
> , but I would suggest
> instead that we remove the implicit "IS" from "NOT".
I agree with this suggestion in a sence that the less implicit things are in a system the less a beginner hits them while learning how to use the system.
Also I have one more suggestion concerning "NOT".I failed to find the "NOT" definition in the maxima info. From school I know that NOT TRUE is FALSE and NOT FALSE is TRUE. This is semantics. From the maxima mailing list
I know that "NOT" calls "IS" implicitly when applied to statements. This
looks like a little bit of syntax, isn't it? Actually, it is not possible
to separate syntax from semantics perfectly. Semantics is final goal of any
syntax. If so, then "NOT" might be equipped with some syntactic skills.
If this does not conflict with the Maxima's internal machinery.
I mean the following, where x,y are algebraic expressions, either defined or
undefined:
NOT x>y evaluates to y>=x
NOT x>=y evaluates to y>x
NOT x=y evaluates to x#y
NOT x#y evaluates to x=y
Similar things may be added for statements about sets and their members.
Having this rools implemented, we exclude things like this
(C1) is((NOT 1>3)=(1<=3));
(D1) FALSE
>From Stavros Macrakis comment (Fri, 12 Dec 2003 11:35:21 -0500):
> "=" and "#" are *syntactic* comparison. Other relations (<, <=,
> etc.) are *semantic* comparison. So Not(x#y) should be False for
> undefined x and y.,
I understant that it is OK with the (C1),(D1), above, but it looks so much
confusing.
In my work, when I need to change a supposition like ASF:3>t to its
opposite, I do the following
ASF:substpart("<=",ASF,0)
Looks clumsy, if compare with ASF:NOT ASF. Additionally, I must remember
that initial OP was ">", not "<".
And things become worse if I need to change between ASF and its negation
several times in a program.
Initially, logical connectors AND, NOT, OR were designated for making
statements from given statements. Is it possible to have this behavior
in Maxima ?
With best regards,
--
Alexander