Implementing a function in a macro?

[Shea Levy]

Hi all,

Is it possible to define a macro that implements another function? I’m trying to write a macro that lets you define a “main” function that takes argc and argv as expected, but also takes views for things like “you have a readable file descriptor at int 0” and “errno is unset” to represent “global” process state that can be changed and tracked linearly. Currently, I have this, which is failing to compile:

(* Set a given function to be the POSIX entry point

 *

 * This is equivalent to implementing main as the passed in function,

 * except that in addition to argc and argv views corresponding to initial

 * global program state in the POSIX environment are passed.

 *

 * Currently, an errno_v ( free ) proof is passed. In the future, proofs

 * corresponding to open file descriptors for stdin, stdout, and stderr will

 * be passed as well

 *)

macdef set_posix_entrypoint ( func ) =

  implement main ( argc, argv ) = let

    extern praxi { v: view } __assert_view (): v

    prval ev = __assert_view < errno_v ( free ) > ()

    val res = ,(func) ( ev | argc, argv )

    extern praxi { v: view } __unassert_view ( x: v ): ()

    prval () = __unassert_view ( ev )

  in res end

I get many errors, but the first one is: 

481(line=12, offs=3) -- 490(line=12, offs=12): error(parsing): the syntactic entity [d0exp] is needed.

(the line and offsets refer to the word “implement” above). It’s unclear to me how to continue, sorry for my ignorance!

Thanks,

Shea

[gmhwxi]

macdef expects a dynamic expression on the right-hand side of '=';
'implement' introduces a declaration. So there is a mismatch here.

Anyways, I feel that 'macdef' is not really meant for this kind of heavy lifting.
Maybe you could implement set_posix_entrypoint in PHP.

[Shea Levy]

Ah ha, I see, thank you.

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