Chaos - Forth-like minimal language

Chaos is a very simple stack-based language designed mainly as a testbed for ColdStore.

In keeping with this, Chaos is able to generate calls to all of the elements of the ColdStore virtual protocol on the objects it creates. It could also function as a nanocode level programming environment for ColdStore.

Chaos has a very simple syntax:

1. Everything in quotes (") is a string constant.
2. Everything in braces {} is a string constant.
3. Everthing beginning with single quote (') is a function reference
4. Everything beginning with a dollar sign ($) is a variable reference.
5. Everything that is a sequence of numerics is an integer constant
6. Everything else is whitespace.

Chaos' semantics are also simple.

• Definition: For the purpose of exposition, the terms TOP and UNDER will be used to denote the values which would be removed from the stack by a 'drop and 'swap 'drop, respectively.
• There is a value stack onto which all constants and the values of all variable references are pushed, and from which all functional arguments are popped.
• There is a namespace within which all variables are stored.
• Any constant is immediately pushed onto the stack.
• Any variable reference is textually replaced with the contents of that variable, which is then pushed onto the stack.
• Any functional reference is either
  • a builtin function, which is evaluated; or
  • the name of a variable, which will be evaluated first as a variable reference, and then as if the value of that variable had been presented as command input.
• Any Error thrown by the underlying ColdStore, including ~underflow, will terminate the execution of the all interpreters, back to Chaos, which will print the Error, then continue with the Error as its TOP.

  ---

  Constants and Variables

  [0-9]+ Digit

  ".*" (String)

  . (Print)

  [A-Za-z_][A-Za-z0-9_]* (Var reference)

  'set

  'new

  ---

  Flow Control

  'fn

  Evaluates TOP as the name of a function, example

  "func" 'fn

  'if

  Evaluates TOP as a boolean, then evaluates one of UNDER or SWAP UNDER as a functional.

  "expr-false" "expr-true" varname 'if

  The stack is reduced by 3 elements.

  'while

  Repeatedly evaluates TOP as a boolean, then evaluates UNDER as a functional

  "body" varname 'while

  The stack is reduced by 1 element, the body of the while is pushed back. Note that the body should regenerate a condition for the next iteration of 'while.

  'eval

  Evaluates TOP as a Chaos expression.

  The stack is reduced by 1 element then modified as per the eval'd expression.

  "'view" 'eval

  'scope

  Evaluates TOP as a Chaos expression in a new interpreter, with a new stack. When the expression has been evaluated, the resultant stack is pushed onto the current stack. Since stacks are ColdStore Lists, this affords one method of creating List objects.

  "1 2 3 4" 'scope

  The stack is reduced by 1 element then increased by the scoped interpreter.

  ---

  Stack Operations

  'dup

  Duplicate the TOP element of the stack

  'drop

  Reduce the stack by one, discarding TOP

  'swap

  Swap TOP and UNDER

  'view

  Render the stack in human readable form.

  'dump

  Render the stack in detailed human readable form.

  ---

  ColdStore environment

  'names

  Push a copy of namespace containing variable definitions

  BEWARE: if you 'dump or 'view while a 'names value is on the stack, Chaos *will* loop forever because the 'names entry contains a copy of Chaos, which contains a copy of the 'names entry. I've no idea how to stop it, short of SIGINT or letting it consume all available memory :)

  However, you can use the fact that the value of the variable Chaos is always the main Chaos interpreter, which is also its Lexer and its stack (as a List), to do some useful introspection:

  "Chaos" 'names 'slice 'length - should be the length of the stack.

  It's not recommended to modify the value of Chaos.

  'this

  Push the current Chaos interpreter (which may or may not be the same as the value of Chaos) onto itself. Again, it's unwise either to 'view the stack, or modify it.

  'builtins

  Push the namespace containing all Registered Builtins

  ---

  Coldstore Object

  'truth

  Replace TOP with its ColdStore truth value.

  'type

  Replace TOP with a String representing its object type.

  'sequence

  Replace TOP with a flattened sequence representation. This representation can be used as an argument to 'new to recreate the object.

  'issequence

  Predicate: does TOP support the Sequence protocol?

  'isiterator

  Predicate: does TOP support the Iterator protocol?

  ---

  Arithmetic Operations

  The following operators have their usual ColdStore definition, and replace TOP, or TOP and UNDER, for

  + 'sum

  - 'sub

  * 'mult

  / 'div

  % 'mod

  'positive

  'negative

  ~ 'invert

  & 'and

  ^ 'xor

  | 'or

  << 'lshift

  >> 'rshift

  == != >= > <= < (Comparisons)

  ---

  Sequence Operations

  'length

  'concat

  'slice

  'element

  'search

  'rreplace - Range replacement

  'replace - Element replacement

  'sreplace - monadic replacement

  'insert

  'del

  'rdel - Range deletion

  ---

  Iterator Operations

  'iterator

  'current

  'more

  'next

  ---

  Functional Operations

  'call

  This will call the nominated Builtin with TOP as its argument. This will likely SigSegv.