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Re: Expressions with ellipsis (...)
*To*: mathgroup at smc.vnet.net
*Subject*: [mg93345] Re: Expressions with ellipsis (...)
*From*: magma <maderri2 at gmail.com>
*Date*: Tue, 4 Nov 2008 06:19:35 -0500 (EST)
*References*: <gdmsbd$jv$1@smc.vnet.net> <200810240630.CAA23066@smc.vnet.net>
On Nov 2, 7:58 am, AES <sieg... at stanford.edu> wrote:
> In article <geh9sa$fb... at smc.vnet.net>, dch888 <dch... at googlemail.com>
> wrote:
>
> > > Another answer is that Mathematica *should* understand the syntax
> > > with ellipsis-- and indeed it can with the facilities of David Park's
> > > Presentations application package.
>
> One has to be careful about the use and interpretation of ellipses.
>
> For example the Mathematica documentation for Compound Expression says
> that
>
> expr_1 ; expr_2 ; =8A
> evaluates the expr_i in turn, giving the last one as t=
he result.
>
> Would this statement, interpreted very literally using a precise
> definition of the ellipsis symbol, cover both
>
> expr_1 ; expr_2 ; expr_3 ; expr_4 ;
>
> and
>
> expr_1 ; expr_2 ; expr_3 ; expr_4
>
> or just one of these? (Which one?)
>
> _Is there_ a precise definition of the ellipsis symbol? (in English, or
> in Mathematica)
>
> Is " ; " technically an expression? (in Mathematica)
The ellipsis symbol has no built-in special meaning in Mathematica. It is used
in CompoundExpression documentation in the same way it is used in
English.
the semicolon ";" is NOT an "expression". It is just the INFIX form of
the CompoundExpression operator, exactly like "+" is the infix form of
Plus
CompoundExpression[a, b, c]
is equivalent to typing
a;b;c
(no semicolon at the end) and WILL display the value of c.
Instead typing
a;b;c;
(semicolon at the end) is equivalent to typing
CompoundExpression[a, b, c;Null]
and WILL NOT display the value of c. In both cases a, b and c are
evaluated.
I do not find this "mystical" or complicated in any way.
But for most Mathematica users, the semicolon can be simply considered a
separator between statements, like similar separators in other
languages.
Actually, to be more precise, the ";" is a "separator and suppressor
of output", while a simple carriage return (the big RETURN key in the
keyboard) is the basic separator between statements. You can see this
by typing
a
b
in the same cell, one below the other (using carriage return). In this
case the evaluations are carried out sequentially and the values are
displayed. The sequence of keypressees:
a "carriage return" b
is not interpreted as
ab
or as
a multiplied by b
, but as
a and then b
So the carriage return is the pure separator of statements.
HOWEVER ".." (just 2 dots) HAS a built-in meaning as Repeated[] and
you can read what it means in the documentation
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