push / pop operation

[ operations ]

operations A sequence of shape operations to execute.

The [ operation pushes the current shape onto the top of the shape stack. It must be matched by a succeeding ] operation, which pops the shape on top of the shape stack and deletes the shape.

Related

centeroperation NILoperation

Examples

Rotation Example

Push Pop a 
Lot -->
    extrude(15)

    r(scopeCenter, 0, 22.5, 0) X.
    r(scopeCenter, 0, 22.5, 0) X.
    r(scopeCenter, 0, 22.5, 0) X.

In this example, the extruded shape is rotated three times and assigned to a new shape (X). The rotations build on each other.

Push Pop b 
Lot -->
    extrude(15)

    [ r(scopeCenter, 0, 22.5, 0) X. ]
    [ r(scopeCenter, 0, 22.5, 0) X. ]
    [ r(scopeCenter, 0, 22.5, 0) X. ]

Encapsulating the rotations and create shape operations with a push/pop pair makes all shapes X coincide. The rotations are independent of each other.

House Example

Push Pop House 
House -->
    extrude(10)
    comp(f) { top : roofHip(45) Roof. | all = House.}

House -->
    [ t(0,10,0) roofHip(45) Roof. ]
    extrude(10)
    comp(f) { top : NIL | all = House. }

Both rules generate the same result. In the second rule, the roof is generated first using push/pop operations.

Translation Example

Push Pop Cylinder 
House-->
    Cylinder
    [ t(  0, 0, ' 1) Cylinder ]
    [ t(  0, 0, '-1) Cylinder ]
    [ t(' 1, 0,   0) Cylinder ]
    [ t('-1, 0,   0) Cylinder ]

Cylinder -->
    primitiveCylinder(16, 1, 2)

Cylinder assets are inserted five times. Each scope is translated based on the scope of the initial shape.

Condition Example

Push Pop Conditional 
Lot -->
    s(1,1,1)
    [ case scope.sx == 1 : primitiveCube() Cube.
      else : primitiveCylinder() Cylinder. ]

Conditional and stochastic statements must not have preceding operations. Use push and pop to encapsulate a case switch.