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Re: "Transparency" with respect to differentiation

• To: mathgroup at smc.vnet.net
• Subject: [mg74088] Re: "Transparency" with respect to differentiation
• From: Martin Schoenecker <ms_usenet at gmx.de>
• Date: Fri, 9 Mar 2007 02:03:47 -0500 (EST)
• Organization: Technische Universitaet Darmstadt
• References: <es909c$2c5$1@smc.vnet.net> <eslrt9$ptl$1@smc.vnet.net> <esolc1$efq$1@smc.vnet.net>

> Does something like the following meet your needs?
> 
> In[1]:=
> quat[(a_) + (b_)] := quat[a] + quat[b];
> quat /: D[quat[fun_], var__] := quat[D[fun, var]];
> Unprotect[D];
> D[quat[(a_) + (b_)], var__] := D[quat[a], var] + D[quat[b], var];
> Protect[D];
> 
> In[6]:=
> quat[f[x] + g[x] + h[x]]
> Out[6]=
> quat[f[x]] + quat[g[x]] + quat[h[x]]

Thank you! Yes, that works perfectly.  I'm just wondering if it was more 
proper style to achieve that without changing the definition of built-in 
commands, i.e. without having to Unprotect[D].  In the meanwhile, I will 
use your approach.

Best Regards,
Martin