private IEnumerable<V> LetVisual(IStream<SExpr> lets)
{
SExpr.Symbol next;
do
{
yield return V.HStack (VAlign.Top, V.Depiction (lets.First), V.Depiction (lets.ItemAt (1)),
V.Label ("="), V.Depiction (lets.ItemAt (2)));
lets = lets.Drop (3);
next = lets.First as SExpr.Symbol;
}
while (next != null && next.Name == "and");
yield return V.HStack (VAlign.Top, V.Depiction (lets.First));
}