Functional Input Arguments to Functions

Allowing functions to be passed as arguments to a function is a useful feature which allows greater generality and re-use. For example, a sorting function may have a comparison function as a formal parameter. This makes the sorting function more general and reusable, since it can adapt to different comparison schemes. For example, the sort function below sorts an array in decreasing or increasing order depending on the passed compare function.

partial function CompareFunc "Function type of the comparison function" input Real x; input Real y; output Boolean comp; end CompareFunc;
function sort "Sorting function using the bubblesort algorithm" input Real[:] arr; input CompareFunc compare; output Real[size(arr,1)] sortedarr; protected Real t; algorithm sortedarr := arr; for i in 1:size(arr,1) loop for j in 1:size(arr,1) loop if not compare(sortedarr[i], sortedarr[j]) then t:= sortedarr[i]; sortedarr[i]:= sortedarr[j]; sortedarr[j]:= t; end if; end for; end for; end sort;
function greaterThan input Real x; input Real y; output Boolean comp = x>y; end greaterThan;
function lessThan input Real x; input Real y; output Boolean comp = x<y; end lessThan;
model SortApplication "Example calls of the sort function" parameter Real[:] ax = {4.0,6.0,2.0,5.0,8.0}; Real[size(ax,1)] xGt; Real[size(ax,1)] xLt; equation xGt = sort(ax, lessThan); // Decreasing order: {8.0,6.0,5.0,4.0,2.0} xLt = sort(ax, greaterThan); // Increasing order: {2.0,4.0,5.0,6.0,8.0} end SortApplication;
simulate(SortApplication)
plot({xGt[1],xGt[2],xGt[3],xGt[4],xGt[5]})