:x = {4}

x={x}

:a = {1,2,3,(x)=4}

:c = a

1={a==c}

a(x)={a(x)}

:! ch a

a(x)={a(x)}

:! ch b

~ x(2) := 3

a(x)={a(x)}

:! ch c

a(x)={a(x)}

~ x:={4}

no={a(x)}