Macro frunk::poly_fn

macro_rules! poly_fn {
    ([$($tparams: tt),*] |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block , $($rest: tt)*) => { ... };
    ([$($tparams: tt, )*] |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block , $($rest: tt)*) => { ... };
    (|$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block, $($rest: tt)*) => { ... };
    (p~ $([$($pars: tt, )*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty $p_body: block , )* ~p f~ $(|$f_args: ident : $f_arg_typ: ty| -> $f_ret_typ: ty $f_body: block , )* ~f [$($tparams: tt),*] |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block , $($rest: tt)*) => { ... };
    (p~ $([$($pars: tt, )*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty { $p_body: block }, )* ~p f~ $(|$f_args: ident : $f_arg_typ: ty| -> $f_ret_typ: ty $f_body: block, )* ~f [$($tparams: tt, )*] |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block, $($rest: tt)*) => { ... };
    (p~ $([$($pars: tt, )*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty $p_body: block, )* ~p f~ $(|$f_args: ident : $f_arg_typ: ty| -> $f_ret_typ: ty $f_body: block, )* ~f |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block, $($rest: tt)*) => { ... };
    (p~ $([$($pars: tt, )*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty $p_body: block, )* ~p f~ $(|$f_args: ident : $f_arg_typ: ty| -> $f_ret_typ: ty $f_body: block, )* ~f [$($tparams: tt),*] |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block) => { ... };
    (p~ $([$($pars: tt, )*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty $p_body: block, )* ~p f~ $(|$f_args: ident : $f_arg_typ: ty| -> $f_ret_typ: ty $f_body: block, )* ~f [$($tparams: tt, )*] |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block) => { ... };
    (p~ $([$($pars: tt)*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty $p_body: block, )* ~p f~ $(|$f_args: ident : $f_arg_typ: ty| -> $f_ret_typ: ty $f_body: block, )* ~f |$arg: ident : $arg_typ: ty| -> $ret_typ: ty $body: block) => { ... };
    (p~ $([$($pars: tt, )*] |$p_args: ident : $p_arg_typ: ty| -> $p_ret_typ: ty $p_body: block, )* ~p f~ $(|$args: ident : $arg_typ: ty| -> $ret_typ: ty $body: block, )* ~f) => { ... };
}

Returns a polymorphic function for use with mapping/folding heterogeneous types.

This macro is intended for use with simple scenarios, and doesn’t handle trait implementation bounds or where clauses (it might in the future when procedural macros land). If it doesn’t work for you, simply implement Func on your own.

Examples

use frunk_core::{Coprod, poly_fn};
type I32F32Str<'a> = Coprod!(i32, f32, &'a str);

let co1 = I32F32Str::inject("lollerskates");
let folded = co1.fold(poly_fn!(
  ['a] |x: &'a str| -> i8 { 1 },
  |x: i32| -> i8 { 2 },
  |f: f32| -> i8 { 3 },
));

assert_eq!(folded, 1);