$ include "seed7_05.s7i";

const func type: stack (in type: baseType) is func
  result
    var type: stackType is void;
  begin
    stackType := array baseType;

    const proc: push (inout stackType: aStack, in baseType: top) is func
      begin
         aStack := [] (top) & aStack;
      end func;

    const func baseType: pop (inout stackType: aStack) is func
      result
        var baseType: top is baseType.value;
      begin
        if length(aStack) = 0 then
          raise RANGE_ERROR;
        else
          top := aStack[1];
          aStack := aStack[2 ..];
        end if;
      end func;

    const func boolean: empty (in stackType: aStack) is
      return length(aStack) = 0;
  end func;

const type: intStack is stack(integer);

const proc: main is func
  local
    var intStack: s is intStack.value;
  begin
    push(s, 10);
    push(s, 20);
    writeln(pop(s) = 20);
    writeln(pop(s) = 10);
    writeln(empty(s));
  end func;