Types, Functions and Methods

Note: An attribute can be:

Single values parameters (string, integer, real, Boolean, dimensions)
A reference to another object (the type of the attribute being the type that must support the object linked through this attribute)
A list of values, or a list of references to other objects.

An object implements one or several types. Implementing means that the object attributes are defined by the type (and its super types). It also means that it can be used at a place where such an object of this type is expected. For example, a mechanical feature (like a Pad) implements both the type of its specification (the Pad) and the type of its result (a solid).

Basic Types

When manipulating an object in EKL, you can read or write its attributes. The basic types hierarchy is described below. The applicative types inherit from this basic hierarchy, and use these types for defining their attributes.

A knowledge type is defined by a set of attributes and methods.

Types are broken down into three main categories:

The types belong to Feature category. This feature abstract type provides a list of attributes available on each object (Name, UserInfo, Children) and a list of methods that can be applied to each object (Access to dynamic attributes, query, find, etc...).

The Literal types, which derive from a common Literal type (Length is a subtype of Literal), cannot have attributes. TLiterals do not have attributes and a limited list of existing Literal Types is avaible.

Note: A constant is an identifier for a simple value. As the name suggests, this value cannot change. The following constants are specified or recognized by the app when programming rules and checks. As a result, they can be used anywhere in a relation in place of the actual values.


`false`	one of the two values that a parameter of Boolean type can have.
`true`	one of the two values that a parameter of Boolean type can have.
PI - 3.141592	The ratio of the circumference of a circle to its diameter.
E- The base of natural logarithm	The constant e is approximately 2.718282.

All types derive from a basic type called ObjectType. If a function takes such a type as argument, you can pass both values and objects. For example, methods and functions related to Lists usually take ObjectType arguments. You can therefore create a list of objects or a list of values (List.setItem(ObjectType)).

Functions

A function is a block of code that accomplishes a specific task and returns a value. A function takes an input, processes it, and returns a result.

When a function is called, no value is copied. Arguments are passed by reference. If you write sin(x), the x variable is directly available in the body of the sinus function.

A variable passed as argument (in input) of a function must be at least a subtype of this function argument or their types must be similar. If you write area(s), s must be a surface. This is also true for the return argument.

The EKL provides a library of functions you can access using the language browser. You can also write your own functions. To know more, see Quality Rules Capture: Working with Reusable Functions.

Methods

A method is a code block associated with a type, and which has access to its attributes.

Attributes and Methods

You can manipulate types through their attributes and methods. To find the attributes and methods of a given type, use the language browser in your app.

Writing and Reading Attributes: An attribute is characterized by its name and its type.


Example 1	Example 2
`sin (x.att)`	`x.att = 4`
The attribute value is first computed and then, it is passed to the function.	The reference of the attribute att of x is passed as variable of the affectation operator. Within this operator, the variable is valuated, thus allowing you to write the value of the attribute att of x.