Design Decisions in the T3X/0 Language
	--------------------------------------

	T3X/0 is an attempt to find the sweet spot between the full
	T3X Release 7 language, as designed in the early 2000's, and
	the much more minimal T3X9 language, as devised in 2017.

	Omissions from T3X Release 7 (T3Xr7)
	------------------------------------

	Object System

	The T3X object system has been removed and replaced by a
	much simpler module system. Unlike T3Xr7 classes T3X/0
	modules are not instantiatable, so there cannot be multiple
	instances of the same module. T3X/0 modules cannot import
	other modules.

	Rationale: instantiation was rarely used. The most prominent
	example was the IOSTREAM class, which was also rarely used.
	Nested modules were used, but are hard to implement on
	systems with limited memory.

	Separate Compilation and External Linking

	T3X/0 does not support separate compilation and external
	linking on all supported platforms, so this can no longer
	considered to be a language feature.

	Rationale: T3X programs tend to be short and fit in a single
	file.

	Runtime Classes

	Some runtime classes of the T3Xr7 language are no longer
	present. The classes removed from the core language include
	the IOStream class, the System class, the TTYCtl class, the
	Util class, and the Xmem class.

	A replacement module exists for the IOStream class. The other
	classes may be implemented as language extentions.

	The String module was refactored to remove some of the more
	heavyweight functions (PARSE, FORMAT) from it.

	Rationale: the core language should be kept small and portable.

	Constant Expression Syntax

	The constant expression syntax has been simplified and is
	now limited to constants, integers, and single instances of
	the the *, *, |, and unary - operators.

	Rationale: Other operators or more complex expressions were
	almost never used, and the constant expression semantics of
	T3Xr7 was a mess.

	Addresses of Global Vectors in Static Tables

	Addresses of global vectors cannot be included in static tables,
	i.e. the following code will be flagged by the T3X/0 compiler:

	VAR s::100;
	DO VAR v; v := [@s]; END

	Rationale: The different memory model of T3X/0 would introduce
	an additional level of redirection. Given

	VAR s::100;
	DO VAR v; v := [@s]; END

	V[0] equals S in T3Xr7 and V[0][0] would be equal to S in T3X/0.
	Therefore, the notation [@vector] is not allowed in T3X/0. In
	order to include the address of a vector in a table, a dynamic
	table has to be used (this also works in T3Xr7):

	VAR s::100;
	DO VAR v; v := [(s)]; END

	Additions to T3X9
	-----------------

	Intrinsic functions were replaced by a simple module system
	and inline (machine-code) functions.

	Rationale: the module system is more flexible, allows to reuse
	frequently-reinvented code, and inline functions make the
	compiler more portable by moving machine-specific parts to an
	external module.

	The unsigned operators (./, .<, etc) were added.

	Rationale: they are necessary on 16-bit systems.

	Additions to T3Xr7
	------------------

	Packed vectors can now contain strings, allowing to write
	PACKED ["FOO"] instead of PACKED['F','O','O'].

	Rationale: Why has this not been added earlier?

	Summary
	-------

	                        T3Xr7       T3X/0       T3X9
	                        --------    --------    --------

	Object System           Yes         No          No

	Modules                 Yes         Simple      No

	Unsigned Operators      Yes         Yes         No

	Constant Expressions    Yes         Simple      Simple

	Intrinsic Functions     No          No          Yes

	Separate Compilation    Yes         Limited     No

	Extern Functions        Yes         Yes         No

	Inline Functions        No          YES         No

	Strings in Bytevectors  No          YES         No

	Classes / Modules

	  T3X Core              Yes         Yes         Subset

	  String                Yes         Yes         No

	  Format and Parse      String      Yes         No

	  Memory                Yes         Yes         No

	  Char                  Yes         Yes         No

	  IOStream              Yes         Yes         No

	  TTYCtl                Yes         No          No

	  System                Yes         No          No

	  Xmem                  Yes         No          No

	  Util                  Yes         No          No