Question: Obtaining power of a function x+y

Dear everyone,

  Hello,

  I have a question about how to get the power 'n' in an expression "(x+y)^n". For instance, I have a Maple code

******

eq1:=4*x^n*y^m+(x+y)^n+x^3;

f1:=map(t -> `if`(match(t = c*y^d, y, 's'), subs(s,d), NULL),
      convert(eq1, list));
f2:=map(t -> `if`(match(t = c*x^d, x, 's'), subs(s,d), NULL),
      convert(eq1, list));
f3:=map(t -> `if`(match(t = c*(x+y)^d, (x+y), 's'), subs(s,d), NULL),
      convert(eq1, list));

************

the output is

*********

                       n  m          n    3
                    4 x  y  + (x + y)  + x
                             [m, 0]
                             [n, 3]
Error, (in unknown) invalid input: match expects its 2nd argument, vv, to be of type {name, set(name)}, but received x+y

*********

what should I do to get the power of x+y?

Thank you very much in advance

with best regards