If you want your code to match what is printed, you should write
f = Function('f')
instead of
f = Function('f')(t)
Alternatively you could use a special printer that prints things as
you want. There is already a printer in the mechanics module that
ignores the (t) part when printing a function (mprint()).
Aaron Meurer
On Thu, Mar 9, 2023 at 8:12 AM Thomas Ligon <[email protected]> wrote:
>
> I am now using Symbol and Function where the name and the value match. That
> was recommended for easier reading and then required for pickle. In order to
> avoid confusing these, I have a different name for Symbol and for Function,
> then I convert them just before printing. My problem is that I am not sure
> how to use this when I take derivatives. When I look at q1S in the debugger I
> see it has type Symbol, but q1F has value q1F(t) and type Q1F (not Function).
> The code looks like this:
> def createSymbols():
> global t, q1S, q2S, q1F, q2F, q1dotS, q2dotS, q1ddotS, q2ddotS
> t = symbols('t')
> q1S, q2S = symbols('q1S, q2S')
> q1dotS, q2dotS = symbols('q1dotS, q2dotS')
> q1ddotS, q2ddotS = symbols('q1ddotS, q2ddotS')
> q1F = Function('q1F')(t)
> q2F = Function('q2F')(t)
> print('end of createSymbols HillCusp')
>
> def symForLatex(expIn):
> expOut = expIn
> expOut = expOut.subs(q1S, symbols('q1'))
> expOut = expOut.subs(q2S, symbols('q2'))
> expOut = expOut.subs(q1F, symbols('q1'))
> expOut = expOut.subs(q2F, symbols('q2'))
> expOut = expOut.subs(q1dotS, symbols('{\dot{q}}_{1}'))
> expOut = expOut.subs(q2dotS, symbols('{\dot{q}}_{2}'))
> expOut = expOut.subs(q1ddotS, symbols('{\ddot{q}}_{1}'))
> expOut = expOut.subs(q2ddotS, symbols('{\ddot{q}}_{2}'))
> return expOut
>
> Here is the code that calculates higher-order derivatives. The second-order
> derivative is defined by Newton's equations (ODEs).
> if qi == 1:
> if nDer == 0:
> retVal = q1F#(t)
> elif nDer == 1:
> retVal = diff(qd(1, 0), t)
> elif nDer == 2:
> retVal = 2*qd(2, 1) + 3*qd(1, 0) - qd(1, 0)*(qd(1, 0)**2 + qd(2,
> 0)**2)**Rational(-3,2)
> else:
> retVal = diff(qd(1, nDer-1), t)
> # replace q1dd & q2dd
> #retVal = retVal.subs(Derivative(q1F(t), (t, 2)), qd(1, 2))
> #retVal = retVal.subs(Derivative(q2F(t), (t, 2)), qd(2, 2))
> retVal = retVal.subs(Derivative(q1F, (t, 2)), qd(1, 2))
> retVal = retVal.subs(Derivative(q2F, (t, 2)), qd(2, 2))
>
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