<Appendix><Heading>A graphical interface</Heading> Here we describe a Tcl/Tk interface to specify numerical semigroups. <Section><Heading>Graphical interface</Heading> <ManSection> <Func Name="XNumericalSemigroup" Arg="[s]"></Func> <Description> This function pops up a Tcl/Tk window which allows the specification of numerical semigroups. The optional argument <A>s</A> is a numerical semigroup whose definition becomes displayed in the graphical interface. <P/> The interface is very simple, it allows to specify a numerical semigroup by its generators or a (proportionally) modular numerical semigroup by its (proportionally) modular condition. The &GAP; variable by which the semigroup will be known must also be specified. <P/> The interface also allows to apply some functions to the semigroup, namely <Ref Func="AperyListOfNumericalSemigroupWRTElement" />, <Ref Func="DrawAperyListOfNumericalSemigroup" />, <Ref Func="SmallElementsOfNumericalSemigroup" />, <Ref Func="GapsOfNumericalSemigroup" />, <Ref Func="FrobeniusNumberOfNumericalSemigroup" /> and <Ref Func="MinimalPresentationOfNumericalSemigroup" />. Finally, it is also possible to add functions to this list and remove them. <Example><![CDATA[ gap> s:=RandomNumericalSemigroup(3,9); <Numerical semigroup with 3 generators> gap> XNumericalSemigroup(s); ]]></Example> This would pop up the following window: <P/> <Alt Only="LaTeX"> \begin{figure}[htbp] \begin{center} \leavevmode \includegraphics{xnumsgp} \end{center} \label{fig:xnumsgp} \end{figure} </Alt> <Alt Only="HTML"> <br><center><img src="xnumsgp.png"></center><br> </Alt> <P/> </Description> </ManSection> </Section> </Appendix>