Re: := vs = in some function definitions
- To: mathgroup at smc.vnet.net
- Subject: [mg113631] Re: := vs = in some function definitions
- From: Sam Takoy <sam.takoy at yahoo.com>
- Date: Fri, 5 Nov 2010 05:12:41 -0500 (EST)
- References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
I'm just following up on this topic, because it's rising up to cause
I'm working on an elaborate project with elements of differential
geometry. So what I have is some global elements describing the geometry
and some functions that represent differential operators. I don't know
what other details to mention. There are many details, but I'm not sure
which ones are relevant and I have not been able to construct a
I try to use "=" rather than ":=" so that as much as possible is
calculated once. For example, I use "curvature[x_, y_]=" rather than
"curvature[x_, y_]:=" because I want it to be calculated once and for
all. The "curvature" function uses some of the global elements
describing the surface.
Then I have a differential operator ddt, defined like this:
ddt0[tensor_][x_, y_] := yadda Derivative[1, 0][tensor][x, y] yadda
and when I use "=" in place of ":=" the code produces the wrong answer.
Why could this be? I have made sure that variables tensor,x,y are not
defined anywhere in the code, but beyond that I can't figure out from
the previous responses what might be causing different action to take place.
Many thanks in advance for giving this long post your attention!
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