Description

This compiler implements

1	Comma expressions for initialisation and increment in for loops
2	Nested function declarations
3	Type declarations
4	Enumerated type notation
5	Check for redeclaration of identifiers in the enumerated type.
	Enumerated type members in different environment from environment in which
	enumerated type created.
6	Member selection for enumerated types
7	Conversion of an enumerated type to a string
8	Addition/subtraction of enumerated type values 
	and increment/decrement of enumerated type variables
9	Comparison of enumerated types
10	Set type declaration
11	Set constructors
12	Set union, difference, intersection, and complement
13	Set membership
14	Comparisons of sets
15	Switch statements with integer, char, and enumerated type values
16	Structured type notation
17	Recursively defined structured types 
	(but not mutual recursion, and not multiple denotations of such types).
18	Field selection
19	Constructors for structures

But does not implement

20	Sets of integers
21	For loops to iterate through sets

It implements member selection of enumerated types so as to permit
field selection as well.

To get a more basic implementation, comment out the grammar rule for
field selection, and uncomment the rule for member selection.

This has the effect of using the code for MemberNode rather than FieldVariableNode.

I have deleted the section parameter from genEnv - 
it was never necessary, and confused some people.

I have moved the creation of declarations into genEnv.
However, declarations are created without a type.

I have replaced genDecl by setType, that sets the type for a declaration,
after it has been declared.

This reorganisation enables the implementation of mutually recursive types, 
although I have never checked whether my implementation actually works.

It is certainly true that checking that two recursive types are equivalent
does not work correctly.  The algorithm will go into infinite recursion.

Programs for testing the main rerquired features are in MarkPrograms, and markrunall.bash
compiles and runs these programs.

Bruce Hutton