variyak 0.2.0

macro to help call variadic functions given a container such as a Vec
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164

/*!

This crate provides a macro `call_variadic` which can be used to construct boilerplate code
to call variadic functions using data from a container such as a Vec.

# Example
```rust,ignore
    let data = vec![1, 2];
    call_variadic!(
        my_func(arg, ...)   // func
        data,               // container
        n,                  // index
        data[n],            // expand
        2,                  // limit
    );

    // Generates:
    //     let container_len = data.len();
    //     match container_len {
    //         0 => my_func(arg),
    //         1 => my_func(arg, {
    //             let n = 0;
    //             data[n]
    //         }),
    //         2 => my_func(
    //             arg,
    //             {
    //                 let n = 0;
    //                 data[n]
    //             },
    //             {
    //                 let n = 1;
    //                 data[n]
    //             },
    //         ),
    //         _ => panic!("expected container size of: 0..=2 got data.len(): {}", container_len)
    //         )),
    //     }
*/

pub mod export {
    pub use seq_macro::seq;
}

/**
Call a variadic function given a container

* func: function call, `...` is the variadic arguments
* container: container identifier
* index: index identifier
* expand: argument expression: get `argument` at index `n`
* limit: maximum number of arguments to expand

# Panics

Panics if size of container is greater than `limit`
*/
#[macro_export]
macro_rules! call_variadic {
    (
        $func:ident $( :: $func_tail:ident )* ( $($args:tt)* ), $container:ident, $index:ident, $($expand:expr)+, $limit:literal
    ) => (
        call_variadic! { @munch
            (func: $func)
            (func_tail: $($func_tail)*)
            (pre: )

            /* to parse */
            (args: $($args)*)

            (container: $container)
            (index: $index)
            (expand: $($expand)+)
            (limit: $limit)
        }
    );

    (@munch
        (func: $func:ident)
        (func_tail: $($func_tail:ident)*)
        (pre: $($pre:tt)*)
        (post: $($post:tt)*)

        (container: $container:ident)
        (index: $index:ident)
        (expand: $($expand:expr)+)
        (limit: $limit:literal)
     ) => (
         $crate::export::seq!(__N in 0..=$limit {{
             let container_len = $container.len();
             match container_len {
                 #(
                     __N => {
                         $crate::export::seq!(__I in 0..__N {
                             $func $(:: $func_tail)* (
                                 $($pre,)*
                                 #( {
                                     let $index = __I;
                                     $($expand)+
                                 },)*
                                 $($post),*
                                 )
                         })
                     }
                  )*
                     _ => {
                         panic!("expected container size of: 0..={} got {}.len(): {}",
                         stringify!($limit),
                         stringify!($container),
                         container_len
                         )
                     }
             }
         }})
    );

    (@munch
        (func: $func:ident)
        (func_tail: $($func_tail:ident)*)
        (pre: $($pre:tt)*)
        (args: ... $(, $post:expr)* $(,)?)

        $container:tt
        $index:tt
        (expand: $($expand:tt)+)
        $limit:tt
    ) => (
        call_variadic! { @munch
            (func: $func)
            (func_tail: $($func_tail)*)
            (pre: $($pre)*)
            (post: $($post)*)

            $container
            $index
            (expand: $($expand)+)
            $limit
        }
    );

    (@munch
        $func:tt
        (func_tail: $($func_tail:tt)*)
        (pre: $($pre:tt)*)
        (args: $expr:expr, $($rest:tt)*)

        $container:tt
        $index:tt
        (expand: $($expand:tt)+)
        $limit:tt
    ) => (
        call_variadic! { @munch
            $func
            (func_tail: $($func_tail)*)
            (pre: $($pre)* $expr)
            (args: $($rest)*)

            $container
            $index
            (expand: $($expand)+)
            $limit
        }
    );
}