sol是起什么作用?

[exitenter4073]

function[sol,eval]=myf(sol,options)
x1=sol(1);
x2=sol(2);
r1=0.1;
r2=0.8;
g1=x1-2*x2+1;
g2=x1.^2/4-gx2.^2+1;
if(g1>=0)&(g2>=0)
eval=(x1-2).^2+(x2-1).^2;
else
eval=(x1-2).^2+(x2-1).^2+r1*g1+r2*g2;
eval=-eval;
end

运行后,提示:
??? Input argument "sol" is undefined.

Error in ==> myf1 at 2
x1=sol(1);