%
% Company control problem
%
% owns(C1, C2, Per) denotes the percentage of shares of
% corporation C2 owned by corporation C1.

%%
export control(Owner, Company).

%%
control(Owner, C)<-owns(Owner, C, Per), Per>49.
control(Owner, C2, sum49<Per>)<-control(Owner, C1), owns(C1,C2,Per).

single(sum49, Y, Y).
multi(sum49, Y, Old, Z)<-Old<49, Z=Old+Y.
return(sum49, Y, Old)<-if (Old = nil then Y>49 else Old+Y>49).

%%
owns(a,b,50).
owns(a,c,61).
owns(b,d,10).
owns(c,d,40).