Green Script - Scripting Kit V1
-------------------------------
*********************************************
TECHNICAL SPECIFICATION: Green Script Opcodes
*********************************************

WARNING: This is preliminary documentation.  It may not be 100%
accurate, and could contain errors.

Value	Name		Parameters
-----------------------------------------------------------------------
0	NOP		None
1	HALT		None
2	LABEL		1 byte:label id
3	GOTO		1 byte:label id
4	GOSUB		1 byte:label id
5	RETURN		None
6	BREAK		None
7	MARK		None
8	ZERO		1 byte:variable id
9	INV		1 byte:variable id
a	LET_VALUE	1 byte:variable id  4 bytes:value
b	LET_VARIABLE	1 byte:variable id  1 byte:variable id
c	ADD_VALUE	1 byte:variable id  4 bytes:value
d	ADD_VARIABLE	1 byte:variable id  1 byte:variable id
e	SUB_VALUE	1 byte:variable id  4 bytes:value
f	SUB_VARIABLE	1 byte:variable id  1 byte:variable id
10	MULT_VALUE	1 byte:variable id  4 bytes:value
11	MULT_VARIABLE	1 byte:variable id  1 byte:variable id
12	DIV_VALUE	1 byte:variable id  4 bytes:value
13	DIV_VARIABLE	1 byte:variable id  1 byte:variable id
14	IF		1 byte:variable id  1 byte:ifcode *....
			....1 byte:data type  (x bytes: data)
15	RETURN_VARIABLE	1 byte:variable id
16	RETURN_VALUE	4 bytes:value
17	PUSH_VALUE	4 bytes:value
18	PUSH_VARIABLE	1 byte:variable id
19	POP_VARIABLE	1 byte:variable id
1a	SIZE		1 byte:variable id
1b	CLEAR		None
1c	SUM		1 byte:variable id
1d	PROD		1 byte:variable id
1e	CLEAR_VALUE	4 bytes:value
1f	CLEAR_VARIABLE	1 byte:variable id
20	INT		1 byte:variable id
21	ABS		1 byte:variable id

 * See ifcodes.txt


******************************************************************
 NOP
******************************************************************
OPCODE VALUE:	0
DATA SIZE:	0
TOTAL SIZE:	1

The "NOP" (NO Operation) command does nothing.
Example:
00


******************************************************************
 HALT
******************************************************************
OPCODE VALUE:	1
DATA SIZE:	0
TOTAL SIZE:	1

The "HALT" command halts execution (not an error exit).
Example:
01


******************************************************************
 LABEL
******************************************************************
OPCODE VALUE:	2
DATA SIZE:	1
TOTAL SIZE:	2

The "LABEL" command is used at compile / assembly / loading time
to use as a "saved offset" - the location of the LABEL opcode is
stored in a table, it's index in that table defined by the byte
following the opcode.
Example:
02 01
When this is discovered, the file offset is stored in entry "01".


******************************************************************
 GOTO
******************************************************************
OPCODE VALUE:	3
DATA SIZE:	1
TOTAL SIZE:	2

The "GOTO" command is used at run time to look up an offset that
is stored in a table, it's index in that table defined by the byte
following the opcode.
Example:
03 01
When this is discovered, the file offset stored in entry "01" is
read and the current read offset is changed to match.


******************************************************************
 GOSUB
******************************************************************
OPCODE VALUE:	4
DATA SIZE:	1
TOTAL SIZE:	2

The "GOSUB" command is exactly the same as the "GOTO" command,
apart from the fact that before jumping to the offset in the table,
the current read offset is added to the top of the "call stack".
Example:
04 01
When this is discovered, the current read location is "pushed"
onto the top of the call stack, then the file offset stored
in entry "01" is read and the current read offset is changed to
match.


******************************************************************
 RETURN
******************************************************************
OPCODE VALUE:	5
DATA SIZE:	0
TOTAL SIZE:	1

The "RETURN" command is used in conjunction with the "GOSUB"
command.   When encountered, the topmost offset is "popped" from
the top of the call stack, and the current read offset is changed
to match.
Example:
05


******************************************************************
 BREAK
******************************************************************
OPCODE VALUE:	6
DATA SIZE:	0
TOTAL SIZE:	1

The "BREAK" command triggers a debug break (works in both debug
and non-debug mode).
Example:
06


******************************************************************
 MARK
******************************************************************
OPCODE VALUE:	7
DATA SIZE:	0
TOTAL SIZE:	1

The "MARK" command triggers a debug mark (works in debug mode
only), which makes the debugger (if present) wait for user input
before continuing.
Example:
07


******************************************************************
 ZERO
******************************************************************
OPCODE VALUE:	8
DATA SIZE:	1
TOTAL SIZE:	2

The "ZERO" command sets the contents of the variable specified by
the byte following the opcode to zero.
Example:
08 01


******************************************************************
 INV
******************************************************************
OPCODE VALUE:	9
DATA SIZE:	1
TOTAL SIZE:	2

The "INV" command reverses the sign of the contents of the variable
specified by the byte following the opcode (i.e. positive values
become negative, and negative values become positive).
Example:
09 01


******************************************************************
 LET_VALUE
******************************************************************
OPCODE VALUE:	a
DATA SIZE:	5
TOTAL SIZE:	6

The "LET_VALUE" command sets the contents of the variable specified
by the byte following the opcode to the floating-point value
specified by the four bytes following the variable id.
Example:
0a 01 ?? ?? ?? ??


******************************************************************
 LET_VARIABLE
******************************************************************
OPCODE VALUE:	b
DATA SIZE:	2
TOTAL SIZE:	3

The "LET_VARIABLE" command copies the contents of the variable
specified two bytes after the opcode into the variable specified
immediately following the opcode.
Example:
0a 02 01


******************************************************************
 ADD_VALUE
******************************************************************
OPCODE VALUE:	c
DATA SIZE:	5
TOTAL SIZE:	6

The "ADD_VALUE" command sets the contents of the variable specified
by adding to it the floating-point value specified by the four
bytes following the variable id.
Example:
0c 01 ?? ?? ?? ??


******************************************************************
 ADD_VARIABLE
******************************************************************
OPCODE VALUE:	d
DATA SIZE:	2
TOTAL SIZE:	3

The "ADD_VARIABLE" command adds the contents of the variable
specified two bytes after the opcode to the variable specified
immediately following the opcode.
Example:
0d 02 01


******************************************************************
 SUB_VALUE
******************************************************************
OPCODE VALUE:	e
DATA SIZE:	5
TOTAL SIZE:	6

The "SUB_VALUE" command sets the contents of the variable specified
by taking from it the floating-point value specified by the four
bytes following the variable id.
Example:
0e 01 ?? ?? ?? ??


******************************************************************
 SUB_VARIABLE
******************************************************************
OPCODE VALUE:	f
DATA SIZE:	2
TOTAL SIZE:	3

The "SUB_VARIABLE" command takes the contents of the variable
specified two bytes after the opcode from the variable specified
immediately following the opcode.
Example:
0f 02 01


******************************************************************
 MULT_VALUE
******************************************************************
OPCODE VALUE:	10
DATA SIZE:	5
TOTAL SIZE:	6

The "MULT_VALUE" command sets the contents of the variable
specified by multiplying it with the floating-point value specified
by the four bytes following the variable id.
Example:
10 01 ?? ?? ?? ??


******************************************************************
 MULT_VARIABLE
******************************************************************
OPCODE VALUE:	11
DATA SIZE:	2
TOTAL SIZE:	3

The "MULT_VARIABLE" command multiplies the contents of the variable
specified two bytes after the opcode with the variable specified
immediately following the opcode, and stores it in the variable
specified immediately after the opcode.
Example:
11 02 01


******************************************************************
 DIV_VALUE
******************************************************************
OPCODE VALUE:	12
DATA SIZE:	5
TOTAL SIZE:	6

The "DIV_VALUE" command divides the contents of the variable
specified immediately after the opcode by the 4-byte floating-
point value specified two bytes after the opcode.
Example:
12 01 ?? ?? ?? ??


******************************************************************
 DIV_VARIABLE
******************************************************************
OPCODE VALUE:	13
DATA SIZE:	2
TOTAL SIZE:	3

The "DIV_VARIABLE" command divides the contents of the variable
specified immediately after the opcode by the contents of the
variable specified two bytes after the opcode.
Example:
13 02 01


******************************************************************
 IF
******************************************************************
OPCODE VALUE:	14
DATA SIZE:	5 or 8
TOTAL SIZE:	6 or 9

The "IF" command is complex, by the fact that the size of the data
following the command can vary, depending on the type of value
that is being compared against (a 4-byte floating-point value, or
a single-byte variable identifier).  Here is the structure:

O      V          I        T              D
                                       ___4-byte float (T=0)
"IF"___Variable___Ifcode___Data Type__/    **OR**
(14)   ID Byte     Byte     ID Byte   \___1-byte variable ID (T=1)

The purpose of the "IF" command is to provide a conditional
operator.  It compares the contents of the variable specified by
"V" to the data specified by "D" using the algebra-based operator
(or "Ifcode") "I".  The size of data "D" varies, depending on the
value of "T", which specifies the data type for "D".  Generally,
"T" is only "0" (meaning a 4-byte float), or "1" (meaning a single
byte variable id, whos contents are to be used in the comparison).
If the result of the expression is "true", then the command that
follows the "IF" command is executed.  However, if the outcome is
"false", the next command is skipped and execution continues two
commands along.
Examples:
14 01 02 01 02
14 01 03 00 ?? ?? ?? ?/

For more information about data type specifiers and ifcodes, see
the "ifcodes.txt" reference file.


******************************************************************
 RETURN_VARIABLE
******************************************************************
OPCODE VALUE:	15
DATA SIZE:	1
TOTAL SIZE:	2

The "RETURN_VARIABLE" command stops execution of the program,
and tells the run-program or debugger the result or "return value"
of the program.  It is extracted from the variable specified by
the byte immediately following the opcode.
Example:
15 01


******************************************************************
 RETURN_VALUE
******************************************************************
OPCODE VALUE:	16
DATA SIZE:	4
TOTAL SIZE:	5

The "RETURN_VALUE" command stops execution of the program,
and tells the run-program or debugger the result or "return value"
of the program.  The result to be given is in 4-byte floating
point value form, and follows the opcode.
Example:
16 ?? ?? ?? ??


******************************************************************
 PUSH_VALUE
******************************************************************
OPCODE VALUE:	17
DATA SIZE:	4
TOTAL SIZE:	5

The "PUSH_VALUE" command adds the 4-byte floating-point value which
follows the opcode to the top of the "user stack".
Example:
17 ?? ?? ?? ??


******************************************************************
 PUSH_VARIABLE
******************************************************************
OPCODE VALUE:	18
DATA SIZE:	1
TOTAL SIZE:	2

The "PUSH_VARIABLE" command adds the contents of the variable
specified by the byte immediately following the opcode to the top
of the "user stack".
Example:
18 01


******************************************************************
 POP_VARIABLE
******************************************************************
OPCODE VALUE:	19
DATA SIZE:	1
TOTAL SIZE:	2

The "POP_VARIABLE" command looks up the value on the top of the
"user stack" (the most recently "PUSH"-ed item), and changes the
value of the variable specified by the byte following the opcode,
to match.  The top item is then removed.
Example:
19 01


******************************************************************
 SIZE
******************************************************************
OPCODE VALUE:	1a
DATA SIZE:	1
TOTAL SIZE:	2

The "SIZE" command looks up the number of items on the "user stack"
(i.e. the SIZE of the stack), and changes the value of the variable
specified by the byte following the opcode to match.
Example:
1a 01


******************************************************************
 CLEAR
******************************************************************
OPCODE VALUE:	1b
DATA SIZE:	0
TOTAL SIZE:	1

The "CLEAR" command is used to remove all items from the "user
stack" (i.e. to CLEAR the stack).
Example:
1b


******************************************************************
 SUM
******************************************************************
OPCODE VALUE:	1c
DATA SIZE:	1
TOTAL SIZE:	2

The "SUM" command performs a "summation" operation.  It adds
togther and finds the total value of all of the items on the "user
stack", and places them in the variable specified by the byte
following the opcode.
Example:
1c 01


******************************************************************
 PROD
******************************************************************
OPCODE VALUE:	1d
DATA SIZE:	1
TOTAL SIZE:	2

The "PROD" command performs a "product" operation.  It multiplies
togther and finds the total product of all of the items on the
"user stack", and places them in the variable specified by the
byte following the opcode.
Example:
1d 01


******************************************************************
 CLEAR_VALUE
******************************************************************
OPCODE VALUE:	1e
DATA SIZE:	4
TOTAL SIZE:	5

The "CLEAR_VALUE" command removes a certain number of items from
the top of the "user stack".  This "certain number" is equal to the
4-byte floating-point value specified immediately after the opcode.
Example:
1e ?? ?? ?? ??


******************************************************************
 CLEAR_VARIABLE
******************************************************************
OPCODE VALUE:	1f
DATA SIZE:	1
TOTAL SIZE:	2

The "CLEAR_VARIABLE" command removes a certain number of items
from the top of the "user stack".  This "certain number" is equal
to the value of the variable specified by the byte following the
opcode.
Example:
1f 01


******************************************************************
 INT
******************************************************************
OPCODE VALUE:	20
DATA SIZE:	1
TOTAL SIZE:	2

The "INT" commands performs an "integer" operation on the variable
specified by the byte following the opcode.  It changes the value
to show only the "whole" part of the number (i.e. removes all
digits from after the decimal point.).  The INT command DOES NOT
round the number up or down.
Example:
20 01


******************************************************************
 ABS
******************************************************************
OPCODE VALUE:	21
DATA SIZE:	1
TOTAL SIZE:	2

The "ABS" commands performs an "absolute" operation on the variable
specified by the byte following the opcode.  It inverts the sign
of the value, changing negative numbers into positive ones, and
positive numbers into negative ones.  A zero remains equal.
Example:
21 01