Can you get one side of an equation and store it in a variable?

Say I have an equation object in Mupad:

eq1 := x + y = 0

Now say after some manipulation I want to drop RHS, and just save the LS in a variable like..

f := left( eq1 )

[Sean de Wolski]

That is Mathcad syntax. Are you using Mathcad?

[Billy]

Sorry, using MuPad

Answer 1

[Walter Roberson]

Within MuPad,

lhs(eq1)

and

rhs(eq1)