MaplePrimes - answers and comments on Question, How do I de-assign a variable?

x:=A : x; unassign('x')

alex_01 — Sat, 13 Jun 2009 01:20:48 Z

x:=A :
x;
unassign('x') :
x ;
A
x

Thanks!

GustavHj — Sat, 13 Jun 2009 01:59:30 Z

Thanks!

another way to unassign a name

Doug Meade — Sat, 13 Jun 2009 02:56:48 Z

If you really want to change the definition, just edit the earlier command and re-execute. There is no need to remove the assignment.

x := 3*sin(y);

Oops. This should have been cos:

x := 3*cos(y);

You do need to unassign a name if you want to completely erase all assignments that have been made to a name. For this I recommend unassign or back quotes:

unassign( 'x' ); # here the single quotes are used to delay evaluation
x:

x := A;
x := `x`;  # but here back quotes are needed to assign the symbol x to the name x (thereby replacing any current value assigned to x)

I hope this provides some additional understanding,

Doug

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Quotes

Joe Riel — Sat, 13 Jun 2009 03:47:01 Z

That is not quite correct. You want to use right quote (forward quotes), not back quotes (left quotes). That is, do

  x := 'x';

Right quotes delay evaluation of an expression, so the rhs of the assignment evaluates to the name rather than its assigned value.

Left quotes are used to express symbols that contain special characters, that is, that not in the expanded alphanumeric set. They have no effect on evaluation, and no effect on a symbol that do not otherwise need them. So `x` is equivalent to x.