Re: Basic questions on _Plus and recursion
- To: mathgroup at smc.vnet.net
- Subject: [mg120887] Re: Basic questions on _Plus and recursion
- From: Heike Gramberg <heike.gramberg at gmail.com>
- Date: Sun, 14 Aug 2011 08:14:57 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <201108131049.GAA25524@smc.vnet.net>
For the second part of your question you could do something like f[a___, b_ /; Scalar[b] == 1, c___] := b f[a, c] example: Scalar[a] = 1; Scalar[c] = 1; f[a, b, c] output: a c f[b] Heike On 13 Aug 2011, at 12:49, Ethan Dyer wrote: > Hi. I'm sure these are common issues, but I haven't found them. Here are the two, unrelated questions. Thank you for the help. > > 1) I want to use _Plus for a function with arbitrary arguments. ie I want: f[a+b]=f[a]+f[b], f[a+b,c+d] to go to f[a,c]+f[a,d]+f[b,c]+f[b,d], ... Is there a standard way to do this? > > 2)Here I want to pull out scalars from a function. Something like this: > > f[x__] :=(Times@@Select[{x},Scalar[#]==1&]) (f@@Select[{x},Scalar[#]!=1&]) > > Where i have defined a function Scalar to =1 for some symbols. > > for instance say I had defined Scalar[a]=1 then f[a,b,c]= a f[b,c]. > > The above does not work, as it gives infinite recursion. Is there a way to do this properly? > > Thank you again. Sorry if these are too common. > > Ethan >
- References:
- Basic questions on _Plus and recursion
- From: Ethan Dyer <ethansdyer@gmail.com>
- Basic questions on _Plus and recursion