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
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
//! A simple set of utility traits for working with tuples

/// Helper trait to allow Appending of tuples
pub trait Append<T> {
    type Output;
    /// Append T onto the end of the tuple returning
    /// a new tuple with the existing elements and T
    fn append(self, T) -> Self::Output;
}

/// Helper trait to allow Perpending of tuples
pub trait Prepend<T> {
    type Output;
    /// Append T onto the start of the tuple returning
    /// a new tuple with all the elements from shifted
    /// over one row and T in the first slot
    fn prepend(self, T) -> Self::Output;
}

macro_rules! tuple_impl {
    // use variables to indicate the arity of the tuple
    ($($from:ident,)*) => {
        // the trailing commas are for the 1 tuple
        impl<$($from,)* T> Append<T> for ( $( $from ,)* ) {
            type Output = ( $( $from ,)*  T);

            #[inline]
            #[allow(non_snake_case)]
            fn append(self, x: T) -> ( $( $from ,)*  T) {
                match self {
                    ($($from,)*) => ($($from,)* x)
                }
            }
        }

        // the trailing commas are for the 1 tuple
        impl<$($from,)*  T> Prepend<T> for ( $( $from ,)* ) {
            type Output = (T, $( $from ,)*);

            #[inline]
            #[allow(non_snake_case)]
            fn prepend(self, x: T) -> (T, $( $from ,)*) {
                match self {
                    ($($from,)*) => (x, $($from,)*)
                }
            }
        }
    }
}

macro_rules! for_each_prefix (
    ($m:ident, [$(($acc:tt),)*], []) => {
        $m!($($acc,)*);
    };
    ($m:ident, [$(($acc:tt),)*], [($arg0:tt), $(($arg:tt),)*]) => {
        $m!($($acc,)*);
        for_each_prefix!($m, [$(($acc),)* ($arg0),], [$(($arg),)*]);
    };
);

for_each_prefix!{
    tuple_impl,
    [],
    [(T0), (T1), (T2), (T3), (T4), (T5), (T6), (T7), (T8), (T9), (T10), (T11), (T12), (T13), (T14), (T15),]
}

macro_rules! merge_impl {
    ([$($a:ident,)*], [$($b:ident,)*]) => {
        // the trailing commas are for the 1 tuple
        impl<$($a,)* $($b,)*> Merge<($($b,)*)> for ( $($a,)* ) {
            type Output = ($($a,)* $($b,)*);

            #[inline]
            #[allow(non_snake_case)]
            fn merge(self, x: ($($b,)*)) -> ($($a,)* $($b,)*) {
                match (self, x) {
                    (($($a,)*), ($($b,)*)) => ($($a,)* $($b,)*)
                }
            }
        }
    };
}

/// Helper trait that allow for merging of tuples
pub trait Merge<T> {
    type Output;
    /// merge LHS with RHS returning a new tuple
    /// that contains the elements of both tuples
    /// ordering is preserved such that LHS elements
    /// come before RHS elements.
    fn merge(self, T) -> Self::Output;
}

macro_rules! for_each_prefix_suffix (
    ($m:ident, [$(($acc:tt),)*], []) => {
        $m!([$($acc,)*], []);
    };
    ($m:ident, [$(($acc:tt),)*], [($arg0:tt), $(($arg:tt),)*]) => {
        $m!([$($acc,)*], [$arg0, $($arg,)*]);
        for_each_prefix_suffix!($m, [$(($acc),)* ($arg0),], [$(($arg),)*]);
    };
);

macro_rules! merge_impl2(
    ($($a: ident,)*) => (
        for_each_prefix_suffix!(
            merge_impl,
            [],
            [$(($a),)*]
        );
    );
);

for_each_prefix!{
    merge_impl2,
    [],
    [(T0), (T1), (T2), (T3), (T4), (T5), (T6), (T7), (T8), (T9), (T10), (T11), (T12), (T13), (T14), (T15),]
}

/// Tries to split a tuple into two tuples
/// if the tuple is odd sized the Right side will
/// contain the extra element
pub trait Split {
    type Left;
    type Right;

    fn split(self) -> (Self::Left, Self::Right);
}

macro_rules! split_impl (
    ($(($a:ident, $b:ident),)*) => (
        impl<$($a,)* $($b,)*> Split for ($($a,)* $($b,)*) {
            type Left = ($($a,)*);
            type Right = ($($b,)*);
            #[allow(non_snake_case)]
            fn split(self) -> (Self::Left, Self::Right) {
                match self {
                    ($($a,)* $($b,)*) => (($($a,)*), ($($b,)*))
                }
            }
        }
        impl<$($a,)* $($b,)* TLast> Split for ($($a,)* $($b,)* TLast,) {
            type Left = ($($a,)*);
            type Right = ($($b,)* TLast,);
            #[allow(non_snake_case)]
            fn split(self) -> (Self::Left, Self::Right) {
                match self {
                    ($($a,)* $($b,)* t_last,) => (($($a,)*), ($($b,)* t_last,))
                }
            }
        }
    );
);

for_each_prefix!{
    split_impl,
    [],
    [((T0, T1)), ((T2, T3)), ((T4, T5)), ((T6, T7)), ((T8, T9)), ((T10, T11)), ((T12, T13)), ((T14, T15)),]
}

#[cfg(test)]
mod test {
    use {Append, Prepend, Merge, Split};

    #[test]
    fn append() {
        let out = (0,).append(1);
        assert_eq!(out.0, 0);
        assert_eq!(out.1, 1);
        let out = out.append(2);
        assert_eq!(out.0, 0);
        assert_eq!(out.1, 1);
        assert_eq!(out.2, 2);
        let out = out.append(3);
        assert_eq!(out.0, 0);
        assert_eq!(out.1, 1);
        assert_eq!(out.2, 2);
        assert_eq!(out.3, 3);
        let out = out.append("foo");
        assert_eq!(out.0, 0);
        assert_eq!(out.1, 1);
        assert_eq!(out.2, 2);
        assert_eq!(out.3, 3);
        assert_eq!(out.4, "foo");
    }

    #[test]
    fn prepend() {
        let out = (0,).prepend(1);
        assert_eq!(out.0, 1);
        assert_eq!(out.1, 0);
        let out = out.prepend(2);
        assert_eq!(out.0, 2);
        assert_eq!(out.1, 1);
        assert_eq!(out.2, 0);
        let out = out.prepend(3);
        assert_eq!(out.0, 3);
        assert_eq!(out.1, 2);
        assert_eq!(out.2, 1);
        assert_eq!(out.3, 0);
        let out = out.prepend("foo");
        assert_eq!(out.0, "foo");
        assert_eq!(out.1, 3);
        assert_eq!(out.2, 2);
        assert_eq!(out.3, 1);
        assert_eq!(out.4, 0);
    }

    #[test]
    fn merge() {
        let a = (1, 2, 3);
        let b = ("foo", "bar");
        let c = a.merge(b);
        assert_eq!(c.0, 1);
        assert_eq!(c.1, 2);
        assert_eq!(c.2, 3);
        assert_eq!(c.3, "foo");
        assert_eq!(c.4, "bar");

        // assert to see if adding an empty
        // tuple results in a tuple.
        let a = ("test",);
        let out = a.merge(());
        assert_eq!(out.0, "test");

        let a = ("test",);
        let out = ().merge(a);
        assert_eq!(out.0, "test");
        assert_eq!(().merge(()), ());
        assert_eq!(().merge((1,)), (1,));
        assert_eq!((1,).merge(()), (1,));
    }

    #[test]
    fn split() {
        let a = (1, 2, 3);
        let (b, c) = a.split();
        assert_eq!(b.0, 1);
        assert_eq!(c.0, 2);
        assert_eq!(c.1, 3);
        assert_eq!(().split(), ((), ()));
        assert_eq!((1,).split(), ((), (1,)));
        assert_eq!((1,2).split(), ((1,), (2,)));
        assert_eq!((1,2,3).split(), ((1,), (2,3)));
    }
}