Re: Question on Thread
- To: mathgroup at smc.vnet.net
- Subject: [mg64436] Re: Question on Thread
- From: dh <dh at metrohm.ch>
- Date: Fri, 17 Feb 2006 04:11:43 -0500 (EST)
- References: <dt1cs8$60$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hello Matt,
I have never fully understood Threads sometime strange behaviour. In any
case, MapThread gives me much less trouble and can do everything Thread can.
Your example would then read:
Clear[f, g]
MapThread[(f[g[#1], #2] &), {{1, 2, 3}, {{a, 1}, {b, 2}, {c, 3}}}]
and this does what one would expect.
Daniel
Matt wrote:
> Hello,
>
> Clear[f]
> Thread[(f[#1, #2] & )[{1, 2, 3}, {{a, 1}, {b, 2}, {c, 3}}]]
>
> Gives the expected output, i.e. {f[1,{a,1}], f[2,{b,2}],...}
>
> but
>
> Clear[f, g]
> Thread[(f[g[#1], #2] & )[{1, 2, 3}, {{a, 1}, {b, 2}, {c, 3}}]]
>
> gives me:
>
> f[g[{1, 2, 3}], {a, 1}], f[g[{1, 2, 3}], {b, 2}], ..., etc.
>
> whereas I would have expected:
>
> f[g[1], {a, 1}], f[g[2], {b, 2}], ..., etc.
>
> I've looked at the 'Thread' documentation and in the Mathematica Book,
> but I can't see why the second case doesn't work.
>
> BTW, I used MapThread as follows, which does work:
>
> MapThread[f[g[#1], #2] & , {{1, 2, 3}, {{a, 1}, {b, 2}, {c, 3}}}
>
> Thanks for your time,
>
> Matt
>