Using Variables in Functions

 

The coordinate functions and the definition interval of the curve are read as strings from an input file, compiled into an internal representation with the function compiler (see section 10.2.8) and evaluated during the computation. The function compiler is also used for other subprojects of Time-Object resp. subclasses of Time_Object, for example for the coordinate functions and the domain data of Explicit and the point coordinates of Surface_Build instances.

Besides the int and double variables provided by the superclass Time_Object the time and the domain variables can be used for functions:

• The time can be referenced with the variable t, it can be used in all functions. If you need for example a definition interval which grows linearly from [0,  ] at time t = 0 to [0, 2 ] at time t = 1 you can use

  0; (1 + t) * pi;

  The constant pi is predefined and can also be used in all functions.
• The domain points can be referenced in the explicit coordinate functions, for curves they are stored in the x variable (see the next section), for surfaces in x and y (see section 8.2.5.1 for an example).
• The variables provided by Time_Object are named i, j, ... and a, b, .... The first int variable in the file corresponds to i, the second to j and so on, the double variables can be referenced with a, b and so on (see also the next section for an example).

There are currently some limitations for the use of the variables, only eight variables (including the time and the domain points) are allowed for each description file and the int and double variables can for example not be used for the domain data. Using a variable which isn't defined or cannot be used will result in an error while reading the input file.