Confused about text format

[ljulliar]

I started writing some wasm code (well actually WAT code) and I'm confused as to what the correct syntax is like I'm seeing wat sample using get_local although the WASM 1.0 spec says local.get. Same for set_local. I have noticed other discrepancies too here and thare

Is it that the WAT samples I'm looking at are outdated or is it that the various WAT -> WASM compilers available right now are not yet compliant with the WASM 1.0 specification ?

Side question: is there a forum for SW development in WASM somewhere ?

Thank you everyone ! (and congrats for making WASM. It's a great initiative)

[rossberg]

Yes, there was a change in naming scheme from get_local to local.get -- and other renamings -- late in the game, so many sources might still use the old syntax.

[ljulliar]

Thank you for that. And for another quick question about text format again. When writing wat code am I supposed to use the S expression style like

(i32.add
(get_local $1)
(i32.const 5)
)

or the stack-based postfix style :
local.get $1
i32.const 5
i32.add

Thanks!

[rossberg]

You use the style you prefer. ;)

[ljulliar]

Ah nice!
Except for the block / loop instructions where you have to use the S-expression style anyway, right ?

[binji]

No, there are different formats for those too:

;; "flat" format
block
  nop
  i32.const 1
  i32.const 2
  i32.add
  drop
end

;; sexpr format
(block
  (nop)
  (drop
    (i32.add (i32.const 1) (i32.const 2)))
)

Same with if and loop too. if has a bit more syntax though:

;; flat format
i32.const 1 ;; condition
if
  nop
else
  nop
end

;; sexpr format
(if
  (i32.const 1)  ;; condition
  (nop)
  (nop)
)

;; alternate sexpr format
(if
  (i32.const 1)
  (then (nop))
  (else (nop))
)

These all produce identical binary output.

[rossberg]

@binji:

;; sexpr format
(if
  (i32.const 1)  ;; condition
  (nop)
  (nop)
)

Actually, we dropped this short form on the way to standardisation.

[binji]

Interesting, I must have missed that change. :)

[ljulliar]

@binji Thanks a lot. That was very helpful. Reading the WASM Standard it isn't obvious that you can use so many different style writing WAT code.

[rossberg]

This has been answered.