Re: Null's not null?
- To: mathgroup at smc.vnet.net
- Subject: [mg69404] Re: [mg69393] Null's not null?
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Mon, 11 Sep 2006 05:38:41 -0400 (EDT)
- Reply-to: hanlonr at cox.net
replaceNullWithEmptyString[x_]:=
(x/._?(ToString[#]=="Null"&):>"");
$PrePrint=replaceNullWithEmptyString[#]&;
a=ReplacePart[Array[x,{4,3}], Null, {2,3}]
{{x[1, 1], x[1, 2], x[1, 3]}, {x[2, 1], x[2, 2], ""}, {x[3, 1], x[3, 2], x[3, 3]},
{x[4, 1], x[4, 2], x[4, 3]}}
Bob Hanlon
---- AES <siegman at stanford.edu> wrote:
> Putting Null into one or more slots in a Table and printing the Table
> shows "Null" (without quotes) at the corresponding positions, as also
> does ToString[Null]. I don't think that's what the Help message says:
>
> "Null is a symbol used to indicate the absence of an
> expression or a result. When it appears as an output
> expression, no output is printed."
>
> I can use a string with a couple of empty spaces ("__") to represent an
> occupied but not empty slot in a Table, but that just looks clumsy to
> me. Is there a truly non-printing Null symbol?
>