Not Enough input arguments

I get the not enough input arguments for a function I made and am trying to pass through ode23. I followed the ode23 syntax but I'm not sure why it is caught up at this point.

My function file:

1-function dydx=solver(x,y)
2-dydx=x-y

How I call my function file:

1-xspan=[0,1];
2-y0=2;
3-
4-[xo,yo]=ode23(solver,xspan,y0)

this also results in an error, supposedly line 4 but it won't say what the error is.

Here are my error messages:

Error using solver (line 2) Not enough input arguments.

Error in ME140_inclassactivity16_runge_kutta (line 4) [xo,yo]=ode23(solver,xspan,y0)

Answer 1

[Andrei Bobrov]

solver = @(t,y)t - y;
xspan = [0,1];
y0 = 2;
[xo,yo] = ode23(solver,xspan,y0);

if solver as m - file (your case):

[xo,yo] = ode23(@solver,xspan,y0);

[Melissa]

Thank you!