Functions

Abstract

While writing equations (i.e., equating two expressions) is sufficient for most modeling, there are cases where a procedural or algorithmic approach, involving explicit assignment, is necessary. To address this need, Modelica includes support for algorithmic functions. While a function in Modelica is like a block because all quantities must be explicitly labeled as either input or output, it is different from a block or model because it is not connected to other components. Instead, it is invoked during the evaluation of expressions. Another difference between a function and a block or model is that a function is not allowed to have any persistent internal state. As a result, there are several restrictions on the statements which can appear within a function (e.g., the der operator cannot appear within a function).