: sq dup * ;

: keep 
    over { call } dip ;

: mag@ 'mag@ print
    'x @ dup print sq 
    'y @ dup print sq
    + sqrt ;

: move@
     'y @ + 'y =@
     'x @ + 'x =@ ;

: :mag
    'mag swap call ;

: :move
    'move swap call ;

: {point-methods} { 
    { dup 'get  = } { pop     @ }
    { dup 'set  = } { pop    =@ }
    { dup 'mag  = } { pop  mag@ }
    { dup 'move = } { pop move@ }
} ;

: [point] 
    {point-methods} [ 'methods @ cond ] { 
        'x 'y 'methods 
    } bind ;

10 20 [point] 'position =@

-7 -16 'position @ { :move } keep :mag