Re: Problem with With
- To: mathgroup at smc.vnet.net
- Subject: [mg80659] Re: Problem with With
- From: Szabolcs <szhorvat at gmail.com>
- Date: Tue, 28 Aug 2007 02:13:05 -0400 (EDT)
- Organization: University of Bergen
- References: <fathcf$3s3$1@smc.vnet.net>
Miguel wrote: > Let the matrix M={{Cos[alfa], -Sin[alfa], 0},{Sin[alfa], Cos[alfa], > 0}, {0, 0, 1}}. > > In[]: > With[{alfa=45=BA}, M] > > Out[]: > > Out[]: {{Cos[alfa], -Sin[alfa], 0},{Sin[alfa], Cos[alfa], 0}, {0, 0, > 1}} > > Mathematica does'nt evaluate the matrix. > > But > > In[]: > {{Cos[alfa], -Sin[alfa], 0},{Sin[alfa], Cos[alfa], 0}, {0, 0, > 1}}/.alfa->45=BA > > works fine. > > Any idea? With With[], the replacement is done *before* M is evaluated. Try using With[{alfa = A}, Evaluate[M]]. Szabolcs