Macros & Constants

Simplifying Path Expressions with Macros

When managing extensive product hierarchies, path expressions are frequently used and can become cumbersome. To streamline the process, the COOM language incorporates the define keyword to support macros. This feature allows for the creation of local macro variables, simplifying the recurrent use of lengthy path expressions. For instance, a macro can be defined to represent the path expression that specifies the bag color.

product {
    Color    color
    ...
    Carrier  carrier
}

structure Carrier {
    Color    carrierColor
    Bag      bag        
}

structure Bag {
    Capacity capacity
    Material material
    Color    color
}

// 'define' introduces a macro for the carrier's bag color
behavior {
    define bagColor = root.carrier.bag.color
    require color = bagColor
}

Here, we define a behavior stating that the bike's color needs to be the same as the color of the bags (included in the carrier structure).

Note that the variables declared by the define keyword are only visible/available in the scope of the current behavior block. If you define a macro inside a block { ... }, it is only visible/available inside that block.

Constants and Formulas

The define keyword can also be used to specify constants or formulas. In the following example the constant PI is defined for being used in calculations:

  structure Circle { 
     num radius
     num area
     num circumference 
  }

  behavior Circle {
     define PI = 3.1415
     define PI_2 = PI * 2

     imply area = radius^2 * PI
     imply circumference = radius * PI_2
  }

It is worth noticing, that a define statement can be used in the definition of another define statement (see PI and PI_2).