WebAssembly has no notion of stacks. Forth has stack manipulation words like: dup swap over drop ... that has no direct equivalent in WebAssembly, and need to be mapped to the local values. Here are some ideas:

1. Parameters stack is i32.
2. All WebAssembly function parameters (fixed count) will be mapped in-order to the Forth parameter stack.
3. All additional (temporal) parameter stack entries will be mapped to the WebAssembly tree leafs of local variables.
4. Function will return (0/1) result on the parameter stack.
5. Additional floating point stack assumed for f64

dup over

In general, dup and over words require temporal local variable in WebAssembly or explicit duplication of source.

: foo ( n -- x ) dup 0= if 1+ then ;

(func $foo (param i32) (result i32)
  (if
    (i32.eq (get_local $0) (i32.const 0))
    (set_local $0
      (i32.add (get_local $0) (i32.const 1))
    )
  )
  (return $0)  
)

Transpile Forth into WAST

MVP

• i32
• PAF subset