Equation -- the class of all equation expressions

Methods that use an equation expression :

• Equation == Equation -- see == -- equality
• Equation == Holder -- see == -- equality
• Holder == Equation -- see == -- equality
• Equation == Expression (missing documentation)
• Expression == Equation (missing documentation)
• not Equation (missing documentation)

For the programmer

The object Equation is a header type, with ancestor classes AssociativeExpression < Expression < BasicList < Thing.