Using fmincon and m-files

Trying to minimize f(x,y)=x^4-x^2+y^2-2x+y

with linear inequality x+y <= 0 and nonlinear inequality x^2+y^2 <= 1

my code

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(in workspace)

objfun=@(x) x(1)^4-x(1)^2+x(2)^2-2*x(1)+x(2);

x0 = [1;-1];

[x,fval]=fmincon(objfun,x0,[1,1],0,[ ],[ ],[ ],[ ],'constraint')

(in m.file ...constraint.m)

function [c,ceq]=constraint(x)

c1=x(1)^2+x(2)^2-1;

ceq=[ ]

===========================================================

Running the code gives:

Warning: The default trust-region-reflective algorithm does not solve problems with the constraints you have specified. FMINCON will use the active-set algorithm instead. For information on applicable algorithms, see Choosing the Algorithm in the documentation.

> In fmincon at 486

Error using feval

Undefined function 'constaint' for input arguments of type 'double'.

Error in fmincon (line 681)

        [ctmp,ceqtmp] = feval(confcn{3},X,varargin{:});

Caused by:

    Failure in initial user-supplied nonlinear constraint function

    evaluation. FMINCON cannot continue.

WHY IS THIS HAPPENING?!