const greater = ( x, y ) => ( x > y ) ? x : y

const isPositive = ( z ) => !!greater( z, 0 )

const isPositiveX = ( x ) => isPositive( x )
const isNegativeX = ( x ) => !isPositiveX( x )

const isPositiveY = ( y ) => isPositive( y )
const isNegativeY = ( y ) => !isPositiveY( y )