Re: Replacement according to the pattern
- To: mathgroup at smc.vnet.net
- Subject: [mg77567] Re: [mg77526] Replacement according to the pattern
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Wed, 13 Jun 2007 07:26:48 -0400 (EDT)
- References: <200706120518.BAA09356@smc.vnet.net>
On Jun 12, 2007, at 1:18 AM, tomuf at seznam.cz wrote: > Hello, > I wanted to parse a big expression and according to some rules > integrate it term by term. For example, I wanted to replace symbol > > HPL[{1, 1, 0}, u] > > where HPL(list,variable) is function from package, with (note that > this simplified example has no mathematical sense) > > HPL[{1, 1, 0}, u] - D[HPL[{1, 1, 0}, u], u] > > i.e. that function minus its derivative with respect to 'u'. I have > loaded package which allows me to differentiate HPL. This works fine. > But when I try to generalize this to handle all lists like {1,1,0} at > the same time so that I don't have to type the rule for all > combinations, the replacement doesn't work well. When I type: > > in = HPL[{1, 1, 0}, u] > in /. HPL[{1, 1, 0}, u] -> HPL[{1, 1, 0}, u] - D[HPL[{1, 1, 0}, u], u] > in /. HPL[a_, u] -> HPL[a, u] - D[HPL[a, u], u] > > the third line produces different result than the second line (the > difference is in the term involving derivative). Does anyone know what > could be wrong? Thanks in advance It's an evaluation order problem; the derivative is taken before the substitution in the second case. in /. HPL[a_, u] :> HPL[a, u] - D[HPL[a, u], u] works. Regards, Ssezi
- References:
- Replacement according to the pattern
- From: tomuf@seznam.cz
- Replacement according to the pattern