Re: Loop programming; how do i do this ???
- To: mathgroup at smc.vnet.net
- Subject: [mg96099] Re: [mg96071] Loop programming; how do i do this ???
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Thu, 5 Feb 2009 04:37:52 -0500 (EST)
- References: <200902041019.FAA18602@smc.vnet.net>
On Feb 4, 2009, at 5:19 AM, plzhlp wrote:
> I need to implement a function into my notebook but am having great
> difficulties even getting started (i'm new to mathematica and
> programming in general)
>
> The function accepts a 1d array (of variable length) of integers
>
> which will refer to a 2d array of constants, of which all need to
> be tested against eachother.
>
> for example:
>
> 1DArrayVar = {2, 4, 5}
>
> 2DArrayCon = {
> {a1,b1,c1},
> {a2,b2,c2},
> {a3,b3,c3},
> {a4,b4,c4},
> {a5,b5,c5}
> }
>
> Function[1DArrayVar]
>
> in this scenario will test:
>
> Do[
> Do[
> Do[
>
> TEST[2DArrayCon[[2,x]],2DArrayCon[[4,y]],2DArrayCon[[5,z]]]
>
> , {x, Length[DArrayCon[[2]]]
> , {y, Length[DArrayCon[[4]]]
> , {z, Length[DArrayCon[[5]]]
>
>
> So basically the problem is that i need a variable amount of nested
> loops, as the length of 1DArrayVar will always be unknown.
>
>> From some research on the internet i've learned a recursive
>> algorithm might be the solution, but i am completely lost on how
>> to start --
>
> any tips would be really appreciated !
I assume the function test has some sort of side effect, because the
return value of a Do expression is Null.
Recursively,
f[constants_,{var_},args__]:=Do[test[args,constants[[var,i]]],
{i,Length[constants[[var]]]}]
f[constants_,vars_,args__]:=Do[f[constants,Rest[vars],Join
[{args},constants[[First[vars],i]]]],{i,Length[constants[[First
[vars]]]]}]
f[constants_,vars_]:=f[constants,vars,{}]
f[constants_,{var_}]:=Do[test[constants[[var,i]]],{i,Length[constants
[[var]]]}]
I think an iterative version is clearer though:
f[constants_,vars_]:=Module[{indices},Do[test[Sequence@@Table
[constants[[vars[[j]],indices[j]]],{j,Length[vars]}]],Evaluate
[Sequence@@Table[{indices[j],Length[constants[[vars[[j]]]]]},{j,Length
[vars]}]]]]
Regards,
Ssezi
- References:
- Loop programming; how do i do this ???
- From: plzhlp <naso@live.be>
- Loop programming; how do i do this ???