private static object getConnectiveString(IBinaryConnective ff)
{
if (ff is And)
{
return("and");
}
else if (ff is Or)
{
return("or");
}
else if (ff is EquivalenceFormula)
{
return("=");
}
else if (ff is Implication)
{
return("=>");
}
throw new Exception();
}
internal static string polish(IBinaryConnective f)
{
var os = getConnectiveString(f);
return("(" + os + " " + polish(f.f1) + " " + polish(f.f2) + ")");
}