Re: Debracketing array symbols
- To: mathgroup at smc.vnet.net
- Subject: [mg92096] Re: [mg92079] Debracketing array symbols
- From: Daniel Lichtblau <danl at wolfram.com>
- Date: Sat, 20 Sep 2008 04:56:55 -0400 (EDT)
- References: <200809190917.FAA15137@smc.vnet.net>
carlos at Colorado.EDU wrote:
> Hi,
>
> For a class project I generate 1D and 2D arrays of arbitrary size with
> entries <letters>[i] and <letters>[i,j] that I need then to convert
> to <letter>i and <letter>ij for export to other languages that do not
> allow brackets in symbol names. E.g.
>
> 1D: {A[1],A[2],A[3],A[4]} -> {A1,A2,A3,A4}
>
> 2D: {{W[1,1],W[1,2]},{W[2,1],W[2,2]}} -> {{W11,W12},{W21,W22}}
>
> Question: would this be the simplest way to do it?
>
> DebracketArrayEntries[Wm_]:=Module[{dim,rep,i,j,n,m,s,Wr},
> rep={"["->"","]"->"",","->""," "->""}; Wr=Wm;
> dim=Length[Dimensions[Wm]];
> If [dim==1,n=Length[Wm]; Print["n=",n];
> For [i=1,i<=n,i++, s=ToString[Wm[[i]]];
> Wr=Wr/.Wm[[i]]->Symbol[StringReplace[s,rep]] ]];
> If [dim==2,{n,m}=Dimensions[Wm];
> For [i=1,i<=n,i++, For[j=1,j<=m,j++, s=ToString[Wm[[i,j]]];
> Wr=Wr/.Wm[[i,j]]->Symbol[StringReplace[s,rep]] ]]];
> Return[Wr]];
>
> The procedural style is to simplify conversion to C++.
If the conversion is to happen within Mathematica, use a simple
replacement rule. Below we do this to get either subscripts or
concatenated variable names.
In[17]:= {{W[1, 1], W[1, 2]}, {W[2, 1], W[2, 2]}} /.
W[aa__] :> Subscript[W, aa]
Out[17]= {{Subscript[W, 1, 1], Subscript[W, 1, 2]}, {Subscript[W, 2,
1], Subscript[W, 2, 2]}}
In[21]:= {{W[1, 1], W[1, 2]}, {W[2, 1], W[2, 2]}} /.
W[aa__] :>
ToExpression[StringJoin[ToString[W], Map[ToString, {aa}]]]
Out[21]= {{W11, W12}, {W21, W22}}
If you intend to do the replacement in C++, I'd say you are better off
coding it in C++ rather than coding in Mathematica and then translating.
Daniel Lichtblau
Wolfram Research
- References:
- Debracketing array symbols
- From: carlos@Colorado.EDU
- Debracketing array symbols