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
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
//-
// Copyright 2017 Jason Lingle
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Support for strategies producing fixed-length arrays.
//!
//! An array of strategies (but only length 1 to 32 for now) is itself a
//! strategy which generates arrays of that size drawing elements from the
//! corresponding input strategies.
//!
//! See also [`UniformArrayStrategy`](struct.UniformArrayStrategy.html) for
//! easily making a strategy for an array drawn from one strategy.
//!
//! General implementations are available for sizes 1 through 32.

use core::marker::PhantomData;

use crate::strategy::*;
use crate::test_runner::*;

/// A `Strategy` which generates fixed-size arrays containing values drawn from
/// an inner strategy.
///
/// `T` must be an array type of length 1 to 32 whose values are produced by
/// strategy `S`. Instances of this type are normally created by the various
/// `uniformXX` functions in this module.
///
/// This is mainly useful when the inner strategy is not `Copy`, precluding
/// expressing the strategy as `[myStrategy; 32]`, for example.
///
/// ## Example
///
/// ```
/// use proptest::prelude::*;
///
/// proptest! {
///   #[test]
///   fn test_something(a in prop::array::uniform32(1u32..)) {
///     let unexpected = [0u32;32];
///     // `a` is also a [u32;32], so we can compare them directly
///     assert_ne!(unexpected, a);
///   }
/// }
/// # fn main() { }
/// ```
#[must_use = "strategies do nothing unless used"]
#[derive(Clone, Copy, Debug)]
pub struct UniformArrayStrategy<S, T> {
    strategy: S,
    _marker: PhantomData<T>,
}

impl<S, T> UniformArrayStrategy<S, T> {
    /// Directly create a `UniformArrayStrategy`.
    ///
    /// This is only intended for advanced use, since the only way to specify
    /// the array size is with the turbofish operator and explicitly naming the
    /// type of the values in the array and the strategy itself.
    ///
    /// Prefer the `uniformXX` functions at module-level unless something
    /// precludes their use.
    pub fn new(strategy: S) -> Self {
        UniformArrayStrategy {
            strategy,
            _marker: PhantomData,
        }
    }
}

/// A `ValueTree` operating over a fixed-size array.
#[derive(Clone, Copy, Debug)]
pub struct ArrayValueTree<T> {
    tree: T,
    shrinker: usize,
    last_shrinker: Option<usize>,
}

macro_rules! small_array {
    ($n:tt $uni:ident : $($ix:expr),*) => {
        /// Create a strategy to generate fixed-length arrays.
        ///
        /// All values within the new strategy are generated using the given
        /// strategy. The length of the array corresponds to the suffix of the
        /// name of this function.
        ///
        /// See [`UniformArrayStrategy`](struct.UniformArrayStrategy.html) for
        /// example usage.
        pub fn $uni<S : Strategy>
            (strategy: S) -> UniformArrayStrategy<S, [S::Value; $n]>
        {
            UniformArrayStrategy {
                strategy,
                _marker: PhantomData
            }
        }

        impl<S : Strategy> Strategy for [S; $n] {
            type Tree = ArrayValueTree<[S::Tree; $n]>;
            type Value = [S::Value; $n];

            fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
                Ok(ArrayValueTree {
                    tree: [$(self[$ix].new_tree(runner)?,)*],
                    shrinker: 0,
                    last_shrinker: None,
                })
            }
        }

        impl<S : Strategy> Strategy
        for UniformArrayStrategy<S, [S::Value; $n]> {
            type Tree = ArrayValueTree<[S::Tree; $n]>;
            type Value = [S::Value; $n];

            fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
                Ok(ArrayValueTree {
                    tree: [$({
                        let _ = $ix;
                        self.strategy.new_tree(runner)?
                    },)*],
                    shrinker: 0,
                    last_shrinker: None,
                })
            }
        }

        impl<T : ValueTree> ValueTree for ArrayValueTree<[T;$n]> {
            type Value = [T::Value;$n];

            fn current(&self) -> [T::Value;$n] {
                [$(self.tree[$ix].current(),)*]
            }

            fn simplify(&mut self) -> bool {
                while self.shrinker < $n {
                    if self.tree[self.shrinker].simplify() {
                        self.last_shrinker = Some(self.shrinker);
                        return true;
                    } else {
                        self.shrinker += 1;
                    }
                }

                false
            }

            fn complicate(&mut self) -> bool {
                if let Some(shrinker) = self.last_shrinker {
                    self.shrinker = shrinker;
                    if self.tree[shrinker].complicate() {
                        true
                    } else {
                        self.last_shrinker = None;
                        false
                    }
                } else {
                    false
                }
            }
        }
    }
}

small_array!(1 uniform1:
             0);
small_array!(2 uniform2:
             0, 1);
small_array!(3 uniform3:
             0, 1, 2);
small_array!(4 uniform4:
             0, 1, 2, 3);
small_array!(5 uniform5:
             0, 1, 2, 3, 4);
small_array!(6 uniform6:
             0, 1, 2, 3, 4, 5);
small_array!(7 uniform7:
             0, 1, 2, 3, 4, 5, 6);
small_array!(8 uniform8:
             0, 1, 2, 3, 4, 5, 6, 7);
small_array!(9 uniform9:
             0, 1, 2, 3, 4, 5, 6, 7, 8);
small_array!(10 uniform10:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
small_array!(11 uniform11:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
small_array!(12 uniform12:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
small_array!(13 uniform13:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
small_array!(14 uniform14:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
small_array!(15 uniform15:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14);
small_array!(16 uniform16:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
small_array!(17 uniform17:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16);
small_array!(18 uniform18:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17);
small_array!(19 uniform19:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18);
small_array!(20 uniform20:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18, 19);
small_array!(21 uniform21:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18, 19, 20);
small_array!(22 uniform22:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18, 19, 20, 21);
small_array!(23 uniform23:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18, 19, 20, 21, 22);
small_array!(24 uniform24:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18, 19, 20, 21, 22, 23);
small_array!(25 uniform25:
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
             18, 19, 20, 21, 22, 23, 24);
small_array!(26 uniform26:
             0, 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);
small_array!(27 uniform27:
             0, 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);
small_array!(28 uniform28:
             0, 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);
small_array!(29 uniform29:
             0, 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);
small_array!(30 uniform30:
             0, 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);
small_array!(31 uniform31:
             0, 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);
small_array!(32 uniform32:
             0, 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);

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn shrinks_fully_ltr() {
        fn pass(a: [i32; 2]) -> bool {
            a[0] * a[1] <= 9
        }

        let input = [0..32, 0..32];
        let mut runner = TestRunner::deterministic();

        let mut cases_tested = 0;
        for _ in 0..256 {
            // Find a failing test case
            let mut case = input.new_tree(&mut runner).unwrap();
            if pass(case.current()) {
                continue;
            }

            loop {
                if pass(case.current()) {
                    if !case.complicate() {
                        break;
                    }
                } else {
                    if !case.simplify() {
                        break;
                    }
                }
            }

            let last = case.current();
            assert!(!pass(last));
            // Maximally shrunken
            assert!(pass([last[0] - 1, last[1]]));
            assert!(pass([last[0], last[1] - 1]));

            cases_tested += 1;
        }

        assert!(cases_tested > 32, "Didn't find enough test cases");
    }

    #[test]
    fn test_sanity() {
        check_strategy_sanity([(0i32..1000), (1i32..1000)], None);
    }
}