Task: Topological sort
C++: #include <map>
#include <set>

template<typename Goal>
class topological_sorter {
protected:
    struct relations {
        std::size_t dependencies;
        std::set<Goal> dependents;
    };
    std::map<Goal, relations> map;
public:
    void add_goal(Goal const &goal) {
        map[goal];
    }
    void add_dependency(Goal const &goal, Goal const &dependency) {
        if (dependency == goal)
            return;
        auto &dependents = map[dependency].dependents;
        if (dependents.find(goal) == dependents.end()) {
            dependents.insert(goal);
            ++map[goal].dependencies;
        }
    }
    template<typename Container>
    void add_dependencies(Goal const &goal, Container const &dependencies) {
        for (auto const &dependency : dependencies)
            add_dependency(goal, dependency);
    }
    template<typename ResultContainer, typename CyclicContainer>
    void destructive_sort(ResultContainer &sorted, CyclicContainer &unsortable) {
        sorted.clear();
        unsortable.clear();
        for (auto const &lookup : map) {
            auto const &goal = lookup.first;
            auto const &relations = lookup.second;
            if (relations.dependencies == 0)
                sorted.push_back(goal);
        }
        for (std::size_t index = 0; index < sorted.size(); ++index)
            for (auto const &goal : map[sorted[index]].dependents)
                if (--map[goal].dependencies == 0)
                    sorted.push_back(goal);
        for (auto const &lookup : map) {
            auto const &goal = lookup.first;
            auto const &relations = lookup.second;
            if (relations.dependencies != 0)
                unsortable.push_back(goal);
        }
    }
    template<typename ResultContainer, typename CyclicContainer>
    void sort(ResultContainer &sorted, CyclicContainer &unsortable) {
        topological_sorter<Goal> temporary = *this;
        temporary.destructive_sort(sorted, unsortable);
    }
    void clear() {
        map.clear();
    }
};



#include <fstream>
#include <sstream>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

void display_heading(string const &message) {
    cout << endl << "~ " << message << " ~" << endl;
}
void display_results(string const &input) {
    topological_sorter<string> sorter;
    vector<string> sorted, unsortable;
    stringstream lines(input);
    string line;
    while (getline(lines, line)) {
        stringstream buffer(line);
        string goal, dependency;
        buffer >> goal;
        sorter.add_goal(goal);
        while (buffer >> dependency)
            sorter.add_dependency(goal, dependency);
    }
    sorter.destructive_sort(sorted, unsortable);
    if (sorted.size() == 0)
        display_heading("Error: no independent variables found!");
    else {
        display_heading("Result");
        for (auto const &goal : sorted)
            cout << goal << endl;
    }
    if (unsortable.size() != 0) {
        display_heading("Error: cyclic dependencies detected!");
        for (auto const &goal : unsortable)
            cout << goal << endl;
    }
}
int main(int argc, char **argv) {
    if (argc == 1) {
        string example = "des_system_lib   std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee\n"
                "dw01             ieee dw01 dware gtech\n"
                "dw02             ieee dw02 dware\n"
                "dw03             std synopsys dware dw03 dw02 dw01 ieee gtech\n"
                "dw04             dw04 ieee dw01 dware gtech\n"
                "dw05             dw05 ieee dware\n"
                "dw06             dw06 ieee dware\n"
                "dw07             ieee dware\n"
                "dware            ieee dware\n"
                "gtech            ieee gtech\n"
                "ramlib           std ieee\n"
                "std_cell_lib     ieee std_cell_lib\n"
                "synopsys\n"
                "cycle_11     cycle_12\n"
                "cycle_12     cycle_11\n"
                "cycle_21     dw01 cycle_22 dw02 dw03\n"
                "cycle_22     cycle_21 dw01 dw04";
        display_heading("Example: each line starts with a goal followed by it's dependencies");
        cout << example << endl;
        display_results(example);
        display_heading("Enter lines of data (press enter when finished)");
        string line, data;
        while (getline(cin, line) && !line.empty())
            data += line + '\n';
        if (!data.empty())
            display_results(data);
    } else
        while (*(++argv)) {
            ifstream file(*argv);
            typedef istreambuf_iterator<char> iterator;
            display_results(string(iterator(file), iterator()));
        }
}

VB: class topological
	dim dictDependencies
	dim dictReported
	dim depth
	
	sub class_initialize
		set dictDependencies = createobject("Scripting.Dictionary")
		set dictReported = createobject("Scripting.Dictionary")
		depth = 0
	end sub
	
	sub reset
		dictReported.removeall
	end sub
	
	property let dependencies( s )
		
		dim i, j ,k
		dim aList
		dim dep
		dim a1
		aList = Split( s, vbNewLine )
		
		do while aList( UBound( aList ) ) = vbnullstring
			redim preserve aList( UBound( aList ) - 1 )
		loop

		for i = lbound( aList ) to ubound( aList )
			aList( i ) = Split( aList( i ), vbTab, 2 )
			a1 = Split( aList( i )( 1 ), " " )
			k = 0
			for j = lbound( a1) to ubound(a1)
				if a1(j) <> aList(i)(0) then
					a1(k) = a1(j)
					k = k + 1
				end if
			next
			redim preserve a1(k-1)
			aList(i)(1) = a1
		next
		for i = lbound( aList ) to ubound( aList )
			dep = aList(i)(0)
			if not dictDependencies.Exists( dep ) then
				dictDependencies.add dep, aList(i)(1)
			end if
		next
		
	end property
	
	sub resolve( s )
		dim i 
		dim deps
		
		depth = depth + 1
		if dictDependencies.Exists(s) then
			deps = dictDependencies(s)
			for i = lbound(deps) to ubound(deps)
				resolve deps(i)
			next
		end if
		if not seen(s) then
			wscript.echo s
			see s
		end if
		depth = depth - 1
	end sub

	function seen( key )
		seen = dictReported.Exists( key )
	end function
	
	sub see( key )
		dictReported.add key, ""
	end sub
	
	property get keys
		keys = dictDependencies.keys
	end property
end class