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Dick Gayler
Dick Gayler

Reputation: 1

creating a subtype of Positive where range is not known until runtime

I am trying to create a graph package for a fixed sized complete graph but the size will not be known until runtime. I want to represent a vertex as a positive in the range 1..num_vertices. I have tried to create a generic graph package with the number of vertices as a generic parameter. This package will have to be instantiated in my code which creates visibility/scope problems for the graph package. Any suggestion? Thank you.

More Detail: Graphs is generic package

num_vertices := 4;
declare
package My_Graphs is new Graphs(num_vertices);
g: My_Graphs.Graph;
begin
...

I need to used My_Graphs in another package that contains graph algorithms.

Upvotes: 0

Views: 72

Answers (1)

Jeffrey R. Carter
Jeffrey R. Carter

Reputation: 3358

Subtype constraints do not have to be static, so you can do things like

Max_Vertices : constant Positive := Some_Input_Function;

subtype Vertex_Number is Positive range 1 .. Max_Vertices;

Upvotes: 4

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