[SOLVED] Forth: What is the standard way to define a word using machine code?

Forth: What is the standard way to define a word using machine code?

I wrote a Forth interpreter in Assembler (core set), but is there a standard way to define a Forth word using Assembler instructions or directly machine code?

Example

I want to define "+" (addition) using Assembler ("::" separate assembler instructions) like this

: + ASMSTART pop hl :: pop de :: add hl de :: push hl ASMEND ;

or directly giving the op codes (for Z80 in this case), which is easier:

: + OPSTART E1 D1 19 E5 OPMEND ;

where ASMSTART-ASMEND and OPSTART-OPMEND are builtin words made for this purpose.

Currently, "+" is a builtin in the interpreter code, like other arithmetic, logical and bit manipulation operations.

Solution

As ruvim says, typically CODE and END-CODE are used for this purpose, analogously to : and ;.

Also, a common way to implement an assembler in Forth is by using a separate vocabulary or wordlist named something like ASSEMBLER, containing words corresponding to assembler mnemonics. This lends itself nicely to an RPN-syntax assembler. So for instance HL could be defined in this vocabulary as a constant, and POP as a word which assembles a pop instruction, using the value from the top of the stack to determine the register operand. Your definition of + could then look something like

ASSEMBLER ALSO
CODE + ( x y -- sum )
   HL POP
   DE POP
   DE HL ADD
   HL PUSH
END-CODE