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Message from discussion calling symbolic expressions, was: Why Sage needs var(...) commands unlike Mathematica?

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More options Nov 7 2008, 6:23 am
From: "John Cremona" <john.crem...@gmail.com>
Date: Fri, 7 Nov 2008 11:23:26 +0000
Local: Fri, Nov 7 2008 6:23 am
Subject: Re: [sage-devel] Re: calling symbolic expressions, was: Why Sage needs var(...) commands unlike Mathematica?
OK so I don't know my alphabet.

2008/11/7 Jason Grout <jason-s...@creativetrax.com>:

> I  think it is very handy to be able to partially evaluate an
> expression.  Do you propose a syntax that lets you effectively do f(5)
> and get a function back?  For example, if I want to plot a level curve
> of f at x=5 presuming that f(x,y)=2*x+3*y, say.  Here are some
> possibilities:

> plot( f(x=5), (y, -10,10))

> plot( f(x=5,y=y), (y, -10,10))

> plot( f(5,None), (y, -10,10))

I prefer this one:

> plot( f(5,y), (y, -10,10))

and it would be even better if y could be replaced by a dummy
variable, like this:  plot( f(f,t), (t,-10,10) )   -- without having
to declare t as a variable too.

John

> g(y) = f(5,y)
> plot(g, (y, -10,10))
> That last one seemed too verbose

> Jason

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