• To: mathgroup at smc.vnet.net
• From: David Bailey <dave at removedbailey.co.uk>
• Date: Wed, 7 Jan 2009 04:12:01 -0500 (EST)
• References: <gjsg8r\$jvp\$1@smc.vnet.net>

```olfa mraihi wrote:
> Hello Mathematica community,
> First, wish you happy new year.
> I want to know how to do these points with mathematica:
>
> 1-reduce: f(f(f(...(v) i times=f(f(f(...(w) j times. I've tried "nest" like this:
> Nest[f,v,i]=C5 Nest[f,w,j]
> , but I have this error:
> Nest::intnm: Non-negative machine-size integer expected at position 3 in Nest[f,v,i] and
> Nest::intnm: Non-negative machine-size integer expected at position 3 in Nest[f,w,j]
> =C2
> 2-I want to use lists symbollically like this: m, mP,l,lP are lists, j,jP,i,iP are variables.By symbolically I mean without specifying the concrete
>  elements and the concrete length of these lists
> i<=iP,j-Length[m]=C5 jP-Length[mP],
> Join[l,m]=C5 Join[lP,mP],
> Nest[Rest,m,i]=C5 Nest[Rest,mP,iP]
>
> 3-when I have j<N and i==j+1 I want mathematica to give me i==N as result.
>
> 4-solve this system of equations: xP = 1 + a/yP=C2  and |yP-xP| <= epsilon
>
> Thank you very much.
> Yours faithfully,
> Olfa MRAIHI
>
To take just one of your requests: The built-in lists in Mathematica are
of fixed length, although the elements themselves can be variables:

{a,b,c}

However, you can write patterns that describe lists of unknown length:

{a,b,c,___}

More generally, I suggest you step back a bit, and describe the actual
problem you are trying to solve.

David Bailey
http://www.dbaileyconsultancy.co.uk

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