├── .gitignore ├── Cargo.toml ├── LICENSE ├── README.md ├── src └── lib.rs └── tests └── tests.rs /.gitignore: -------------------------------------------------------------------------------- 1 | # Generated by Cargo 2 | # will have compiled files and executables 3 | /target/ 4 | 5 | # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries 6 | # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html 7 | Cargo.lock 8 | 9 | # These are backup files generated by rustfmt 10 | **/*.rs.bk 11 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "standard-dist" 3 | version = "1.0.0" 4 | authors = ["Nathan West "] 5 | edition = "2018" 6 | 7 | readme = "README.md" 8 | license = "MPL-2.0" 9 | description = "Derivable random distributions for types" 10 | repository = "https://github.com/Lucretiel/standard-dist" 11 | 12 | # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html 13 | 14 | [lib] 15 | proc-macro = true 16 | 17 | [dependencies] 18 | itertools = "0.10.0" 19 | proc-macro2 = "1.0.26" 20 | quote = "1.0.9" 21 | syn = {version = "1.0.72", features = ["extra-traits", "full"]} 22 | 23 | [dev-dependencies] 24 | once_cell = "1.7.2" 25 | rand = "0.8.3" 26 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Mozilla Public License Version 2.0 2 | ================================== 3 | 4 | 1. Definitions 5 | -------------- 6 | 7 | 1.1. "Contributor" 8 | means each individual or legal entity that creates, contributes to 9 | the creation of, or owns Covered Software. 10 | 11 | 1.2. "Contributor Version" 12 | means the combination of the Contributions of others (if any) used 13 | by a Contributor and that particular Contributor's Contribution. 14 | 15 | 1.3. "Contribution" 16 | means Covered Software of a particular Contributor. 17 | 18 | 1.4. "Covered Software" 19 | means Source Code Form to which the initial Contributor has attached 20 | the notice in Exhibit A, the Executable Form of such Source Code 21 | Form, and Modifications of such Source Code Form, in each case 22 | including portions thereof. 23 | 24 | 1.5. "Incompatible With Secondary Licenses" 25 | means 26 | 27 | (a) that the initial Contributor has attached the notice described 28 | in Exhibit B to the Covered Software; or 29 | 30 | (b) that the Covered Software was made available under the terms of 31 | version 1.1 or earlier of the License, but not also under the 32 | terms of a Secondary License. 33 | 34 | 1.6. "Executable Form" 35 | means any form of the work other than Source Code Form. 36 | 37 | 1.7. "Larger Work" 38 | means a work that combines Covered Software with other material, in 39 | a separate file or files, that is not Covered Software. 40 | 41 | 1.8. "License" 42 | means this document. 43 | 44 | 1.9. "Licensable" 45 | means having the right to grant, to the maximum extent possible, 46 | whether at the time of the initial grant or subsequently, any and 47 | all of the rights conveyed by this License. 48 | 49 | 1.10. "Modifications" 50 | means any of the following: 51 | 52 | (a) any file in Source Code Form that results from an addition to, 53 | deletion from, or modification of the contents of Covered 54 | Software; or 55 | 56 | (b) any new file in Source Code Form that contains any Covered 57 | Software. 58 | 59 | 1.11. "Patent Claims" of a Contributor 60 | means any patent claim(s), including without limitation, method, 61 | process, and apparatus claims, in any patent Licensable by such 62 | Contributor that would be infringed, but for the grant of the 63 | License, by the making, using, selling, offering for sale, having 64 | made, import, or transfer of either its Contributions or its 65 | Contributor Version. 66 | 67 | 1.12. "Secondary License" 68 | means either the GNU General Public License, Version 2.0, the GNU 69 | Lesser General Public License, Version 2.1, the GNU Affero General 70 | Public License, Version 3.0, or any later versions of those 71 | licenses. 72 | 73 | 1.13. "Source Code Form" 74 | means the form of the work preferred for making modifications. 75 | 76 | 1.14. "You" (or "Your") 77 | means an individual or a legal entity exercising rights under this 78 | License. For legal entities, "You" includes any entity that 79 | controls, is controlled by, or is under common control with You. For 80 | purposes of this definition, "control" means (a) the power, direct 81 | or indirect, to cause the direction or management of such entity, 82 | whether by contract or otherwise, or (b) ownership of more than 83 | fifty percent (50%) of the outstanding shares or beneficial 84 | ownership of such entity. 85 | 86 | 2. License Grants and Conditions 87 | -------------------------------- 88 | 89 | 2.1. Grants 90 | 91 | Each Contributor hereby grants You a world-wide, royalty-free, 92 | non-exclusive license: 93 | 94 | (a) under intellectual property rights (other than patent or trademark) 95 | Licensable by such Contributor to use, reproduce, make available, 96 | modify, display, perform, distribute, and otherwise exploit its 97 | Contributions, either on an unmodified basis, with Modifications, or 98 | as part of a Larger Work; and 99 | 100 | (b) under Patent Claims of such Contributor to make, use, sell, offer 101 | for sale, have made, import, and otherwise transfer either its 102 | Contributions or its Contributor Version. 103 | 104 | 2.2. Effective Date 105 | 106 | The licenses granted in Section 2.1 with respect to any Contribution 107 | become effective for each Contribution on the date the Contributor first 108 | distributes such Contribution. 109 | 110 | 2.3. Limitations on Grant Scope 111 | 112 | The licenses granted in this Section 2 are the only rights granted under 113 | this License. No additional rights or licenses will be implied from the 114 | distribution or licensing of Covered Software under this License. 115 | Notwithstanding Section 2.1(b) above, no patent license is granted by a 116 | Contributor: 117 | 118 | (a) for any code that a Contributor has removed from Covered Software; 119 | or 120 | 121 | (b) for infringements caused by: (i) Your and any other third party's 122 | modifications of Covered Software, or (ii) the combination of its 123 | Contributions with other software (except as part of its Contributor 124 | Version); or 125 | 126 | (c) under Patent Claims infringed by Covered Software in the absence of 127 | its Contributions. 128 | 129 | This License does not grant any rights in the trademarks, service marks, 130 | or logos of any Contributor (except as may be necessary to comply with 131 | the notice requirements in Section 3.4). 132 | 133 | 2.4. Subsequent Licenses 134 | 135 | No Contributor makes additional grants as a result of Your choice to 136 | distribute the Covered Software under a subsequent version of this 137 | License (see Section 10.2) or under the terms of a Secondary License (if 138 | permitted under the terms of Section 3.3). 139 | 140 | 2.5. Representation 141 | 142 | Each Contributor represents that the Contributor believes its 143 | Contributions are its original creation(s) or it has sufficient rights 144 | to grant the rights to its Contributions conveyed by this License. 145 | 146 | 2.6. Fair Use 147 | 148 | This License is not intended to limit any rights You have under 149 | applicable copyright doctrines of fair use, fair dealing, or other 150 | equivalents. 151 | 152 | 2.7. Conditions 153 | 154 | Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted 155 | in Section 2.1. 156 | 157 | 3. Responsibilities 158 | ------------------- 159 | 160 | 3.1. Distribution of Source Form 161 | 162 | All distribution of Covered Software in Source Code Form, including any 163 | Modifications that You create or to which You contribute, must be under 164 | the terms of this License. You must inform recipients that the Source 165 | Code Form of the Covered Software is governed by the terms of this 166 | License, and how they can obtain a copy of this License. You may not 167 | attempt to alter or restrict the recipients' rights in the Source Code 168 | Form. 169 | 170 | 3.2. Distribution of Executable Form 171 | 172 | If You distribute Covered Software in Executable Form then: 173 | 174 | (a) such Covered Software must also be made available in Source Code 175 | Form, as described in Section 3.1, and You must inform recipients of 176 | the Executable Form how they can obtain a copy of such Source Code 177 | Form by reasonable means in a timely manner, at a charge no more 178 | than the cost of distribution to the recipient; and 179 | 180 | (b) You may distribute such Executable Form under the terms of this 181 | License, or sublicense it under different terms, provided that the 182 | license for the Executable Form does not attempt to limit or alter 183 | the recipients' rights in the Source Code Form under this License. 184 | 185 | 3.3. Distribution of a Larger Work 186 | 187 | You may create and distribute a Larger Work under terms of Your choice, 188 | provided that You also comply with the requirements of this License for 189 | the Covered Software. If the Larger Work is a combination of Covered 190 | Software with a work governed by one or more Secondary Licenses, and the 191 | Covered Software is not Incompatible With Secondary Licenses, this 192 | License permits You to additionally distribute such Covered Software 193 | under the terms of such Secondary License(s), so that the recipient of 194 | the Larger Work may, at their option, further distribute the Covered 195 | Software under the terms of either this License or such Secondary 196 | License(s). 197 | 198 | 3.4. Notices 199 | 200 | You may not remove or alter the substance of any license notices 201 | (including copyright notices, patent notices, disclaimers of warranty, 202 | or limitations of liability) contained within the Source Code Form of 203 | the Covered Software, except that You may alter any license notices to 204 | the extent required to remedy known factual inaccuracies. 205 | 206 | 3.5. Application of Additional Terms 207 | 208 | You may choose to offer, and to charge a fee for, warranty, support, 209 | indemnity or liability obligations to one or more recipients of Covered 210 | Software. However, You may do so only on Your own behalf, and not on 211 | behalf of any Contributor. You must make it absolutely clear that any 212 | such warranty, support, indemnity, or liability obligation is offered by 213 | You alone, and You hereby agree to indemnify every Contributor for any 214 | liability incurred by such Contributor as a result of warranty, support, 215 | indemnity or liability terms You offer. You may include additional 216 | disclaimers of warranty and limitations of liability specific to any 217 | jurisdiction. 218 | 219 | 4. Inability to Comply Due to Statute or Regulation 220 | --------------------------------------------------- 221 | 222 | If it is impossible for You to comply with any of the terms of this 223 | License with respect to some or all of the Covered Software due to 224 | statute, judicial order, or regulation then You must: (a) comply with 225 | the terms of this License to the maximum extent possible; and (b) 226 | describe the limitations and the code they affect. Such description must 227 | be placed in a text file included with all distributions of the Covered 228 | Software under this License. Except to the extent prohibited by statute 229 | or regulation, such description must be sufficiently detailed for a 230 | recipient of ordinary skill to be able to understand it. 231 | 232 | 5. Termination 233 | -------------- 234 | 235 | 5.1. The rights granted under this License will terminate automatically 236 | if You fail to comply with any of its terms. However, if You become 237 | compliant, then the rights granted under this License from a particular 238 | Contributor are reinstated (a) provisionally, unless and until such 239 | Contributor explicitly and finally terminates Your grants, and (b) on an 240 | ongoing basis, if such Contributor fails to notify You of the 241 | non-compliance by some reasonable means prior to 60 days after You have 242 | come back into compliance. Moreover, Your grants from a particular 243 | Contributor are reinstated on an ongoing basis if such Contributor 244 | notifies You of the non-compliance by some reasonable means, this is the 245 | first time You have received notice of non-compliance with this License 246 | from such Contributor, and You become compliant prior to 30 days after 247 | Your receipt of the notice. 248 | 249 | 5.2. If You initiate litigation against any entity by asserting a patent 250 | infringement claim (excluding declaratory judgment actions, 251 | counter-claims, and cross-claims) alleging that a Contributor Version 252 | directly or indirectly infringes any patent, then the rights granted to 253 | You by any and all Contributors for the Covered Software under Section 254 | 2.1 of this License shall terminate. 255 | 256 | 5.3. In the event of termination under Sections 5.1 or 5.2 above, all 257 | end user license agreements (excluding distributors and resellers) which 258 | have been validly granted by You or Your distributors under this License 259 | prior to termination shall survive termination. 260 | 261 | ************************************************************************ 262 | * * 263 | * 6. Disclaimer of Warranty * 264 | * ------------------------- * 265 | * * 266 | * Covered Software is provided under this License on an "as is" * 267 | * basis, without warranty of any kind, either expressed, implied, or * 268 | * statutory, including, without limitation, warranties that the * 269 | * Covered Software is free of defects, merchantable, fit for a * 270 | * particular purpose or non-infringing. The entire risk as to the * 271 | * quality and performance of the Covered Software is with You. * 272 | * Should any Covered Software prove defective in any respect, You * 273 | * (not any Contributor) assume the cost of any necessary servicing, * 274 | * repair, or correction. This disclaimer of warranty constitutes an * 275 | * essential part of this License. No use of any Covered Software is * 276 | * authorized under this License except under this disclaimer. * 277 | * * 278 | ************************************************************************ 279 | 280 | ************************************************************************ 281 | * * 282 | * 7. Limitation of Liability * 283 | * -------------------------- * 284 | * * 285 | * Under no circumstances and under no legal theory, whether tort * 286 | * (including negligence), contract, or otherwise, shall any * 287 | * Contributor, or anyone who distributes Covered Software as * 288 | * permitted above, be liable to You for any direct, indirect, * 289 | * special, incidental, or consequential damages of any character * 290 | * including, without limitation, damages for lost profits, loss of * 291 | * goodwill, work stoppage, computer failure or malfunction, or any * 292 | * and all other commercial damages or losses, even if such party * 293 | * shall have been informed of the possibility of such damages. This * 294 | * limitation of liability shall not apply to liability for death or * 295 | * personal injury resulting from such party's negligence to the * 296 | * extent applicable law prohibits such limitation. Some * 297 | * jurisdictions do not allow the exclusion or limitation of * 298 | * incidental or consequential damages, so this exclusion and * 299 | * limitation may not apply to You. * 300 | * * 301 | ************************************************************************ 302 | 303 | 8. Litigation 304 | ------------- 305 | 306 | Any litigation relating to this License may be brought only in the 307 | courts of a jurisdiction where the defendant maintains its principal 308 | place of business and such litigation shall be governed by laws of that 309 | jurisdiction, without reference to its conflict-of-law provisions. 310 | Nothing in this Section shall prevent a party's ability to bring 311 | cross-claims or counter-claims. 312 | 313 | 9. Miscellaneous 314 | ---------------- 315 | 316 | This License represents the complete agreement concerning the subject 317 | matter hereof. If any provision of this License is held to be 318 | unenforceable, such provision shall be reformed only to the extent 319 | necessary to make it enforceable. Any law or regulation which provides 320 | that the language of a contract shall be construed against the drafter 321 | shall not be used to construe this License against a Contributor. 322 | 323 | 10. Versions of the License 324 | --------------------------- 325 | 326 | 10.1. New Versions 327 | 328 | Mozilla Foundation is the license steward. Except as provided in Section 329 | 10.3, no one other than the license steward has the right to modify or 330 | publish new versions of this License. Each version will be given a 331 | distinguishing version number. 332 | 333 | 10.2. Effect of New Versions 334 | 335 | You may distribute the Covered Software under the terms of the version 336 | of the License under which You originally received the Covered Software, 337 | or under the terms of any subsequent version published by the license 338 | steward. 339 | 340 | 10.3. Modified Versions 341 | 342 | If you create software not governed by this License, and you want to 343 | create a new license for such software, you may create and use a 344 | modified version of this License if you rename the license and remove 345 | any references to the name of the license steward (except to note that 346 | such modified license differs from this License). 347 | 348 | 10.4. Distributing Source Code Form that is Incompatible With Secondary 349 | Licenses 350 | 351 | If You choose to distribute Source Code Form that is Incompatible With 352 | Secondary Licenses under the terms of this version of the License, the 353 | notice described in Exhibit B of this License must be attached. 354 | 355 | Exhibit A - Source Code Form License Notice 356 | ------------------------------------------- 357 | 358 | This Source Code Form is subject to the terms of the Mozilla Public 359 | License, v. 2.0. If a copy of the MPL was not distributed with this 360 | file, You can obtain one at http://mozilla.org/MPL/2.0/. 361 | 362 | If it is not possible or desirable to put the notice in a particular 363 | file, then You may include the notice in a location (such as a LICENSE 364 | file in a relevant directory) where a recipient would be likely to look 365 | for such a notice. 366 | 367 | You may add additional accurate notices of copyright ownership. 368 | 369 | Exhibit B - "Incompatible With Secondary Licenses" Notice 370 | --------------------------------------------------------- 371 | 372 | This Source Code Form is "Incompatible With Secondary Licenses", as 373 | defined by the Mozilla Public License, v. 2.0. 374 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # standard-dist 2 | 3 | An attribute macro for creating a `Standard` distribution for rust types 4 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | /*! 2 | `standard-dist` is a library for automatically deriving a `rand` standard 3 | distribution for your types via a derive macro. 4 | 5 | # Usage examples 6 | 7 | ``` 8 | use rand::distributions::Uniform; 9 | use standard_dist::StandardDist; 10 | 11 | // Select heads or tails with equal probability 12 | #[derive(Debug, Clone, Copy, PartialEq, Eq, StandardDist)] 13 | enum Coin { 14 | Heads, 15 | Tails, 16 | } 17 | 18 | // Flip 3 coins, independently 19 | #[derive(Debug, Clone, Copy, PartialEq, Eq, StandardDist)] 20 | struct Coins { 21 | first: Coin, 22 | second: Coin, 23 | third: Coin, 24 | } 25 | 26 | // Use the `#[distribution]` attribute to customize the distribution used on 27 | // a field 28 | #[derive(Debug, Clone, Copy, PartialEq, Eq, StandardDist)] 29 | struct Die { 30 | #[distribution(Uniform::from(1..=6))] 31 | value: u8 32 | } 33 | 34 | // Use the `#[weight]` attribute to customize the relative probabilities of 35 | // enum variants 36 | #[derive(Debug, Clone, Copy, PartialEq, Eq, StandardDist)] 37 | enum D20 { 38 | #[weight(18)] 39 | Normal, 40 | 41 | Critical, 42 | CriticalFail, 43 | } 44 | ``` 45 | 46 | [`rand`] generates typed random values via the [`Distribution`] trait, which 47 | uses a [source of randomness] to produce values of the given type. Of particular 48 | note is the [`Standard`] distribution, which is the stateless "default" way to 49 | produce random values of a particular type. For instance: 50 | - For ints, this randomly chooses from all possible values for that int type 51 | - For bools, it chooses true or false with 50/50 probability 52 | - For `Option`, it chooses `None` or `Some` with 50/50 probability, and uses 53 | [`Standard`] to randomly populate the inner `Some` value. 54 | 55 | # Structs 56 | 57 | When you derive `StandardDist` for one of your own structs, it creates an 58 | `impl Distribution for Standard` implementation, allowing you to 59 | create randomized instances of the struct via [`Rng::gen`]. This implementation 60 | will in turn use the `Standard` distribution to populate all the fields of 61 | your type. 62 | 63 | ```rust 64 | use standard_dist::StandardDist; 65 | 66 | #[derive(StandardDist)] 67 | struct SimpleStruct { 68 | coin: bool, 69 | percent: f64, 70 | } 71 | 72 | let mut heads = 0; 73 | 74 | for _ in 0..2000 { 75 | let s: SimpleStruct = rand::random(); 76 | assert!(0.0 <= s.percent); 77 | assert!(s.percent < 1.0); 78 | if s.coin { 79 | heads += 1; 80 | } 81 | } 82 | 83 | assert!(900 < heads, "heads: {}", heads); 84 | assert!(heads < 1100, "heads: {}", heads); 85 | ``` 86 | 87 | ## Custom Distributions 88 | 89 | You can customize the distribution used for any field with the `#[distribution]` 90 | attribute: 91 | 92 | ```rust 93 | use std::collections::HashMap; 94 | use standard_dist::StandardDist; 95 | use rand::distributions::Uniform; 96 | 97 | #[derive(StandardDist)] 98 | struct Die { 99 | #[distribution(Uniform::from(1..=6))] 100 | value: u8 101 | } 102 | 103 | let mut counter: HashMap = HashMap::new(); 104 | 105 | for _ in 0..6000 { 106 | let die: Die = rand::random(); 107 | *counter.entry(die.value).or_insert(0) += 1; 108 | } 109 | 110 | assert_eq!(counter.len(), 6); 111 | 112 | for i in 1..=6 { 113 | let count = counter[&i]; 114 | assert!(900 < count, "{}: {}", i, count); 115 | assert!(count < 1100, "{}: {}", i, count); 116 | } 117 | ``` 118 | 119 | # Enums 120 | 121 | When applied to an enum type, the implementation will randomly select a variant 122 | (where each variant has an equal probability) and then populate all the fields 123 | of that variant in the same manner as with a struct. Enum variant fields may 124 | have custom distributions applied via `#[distribution]`, just like struct 125 | fields. 126 | 127 | ```rust 128 | use standard_dist::StandardDist; 129 | 130 | #[derive(PartialEq, Eq, StandardDist)] 131 | enum Coin { 132 | Heads, 133 | Tails, 134 | } 135 | 136 | let mut heads = 0; 137 | 138 | for _ in 0..2000 { 139 | let coin: Coin = rand::random(); 140 | if coin == Coin::Heads { 141 | heads += 1; 142 | } 143 | } 144 | 145 | assert!(900 < heads, "heads: {}", heads); 146 | assert!(heads < 1100, "heads: {}", heads); 147 | ``` 148 | 149 | ## Weights 150 | 151 | Enum variants may be weighted with the `#[weight]` attribute to make them 152 | relatively more or less likely to be randomly selected. A weight of 0 means 153 | that the variant will never be selected. Any untagged variants will have a 154 | weight of 1. 155 | 156 | ```rust 157 | use standard_dist::StandardDist; 158 | 159 | #[derive(StandardDist)] 160 | enum D20 { 161 | #[weight(18)] 162 | Normal, 163 | 164 | CriticalHit, 165 | CriticalMiss, 166 | } 167 | 168 | let mut crits = 0; 169 | 170 | for _ in 0..20000 { 171 | let roll: D20 = rand::random(); 172 | if matches!(roll, D20::CriticalHit) { 173 | crits += 1; 174 | } 175 | } 176 | 177 | assert!(900 < crits, "crits: {}", crits); 178 | assert!(crits < 1100, "crits: {}", crits); 179 | ``` 180 | 181 | # Advanced custom distributions 182 | 183 | ## Distribution types 184 | 185 | You may optionally explicitly specify a type for your distributions; this can 186 | sometimes be necessary when using generic types. 187 | 188 | ```rust 189 | use std::collections::HashMap; 190 | use standard_dist::StandardDist; 191 | use rand::distributions::Uniform; 192 | 193 | #[derive(StandardDist)] 194 | struct Die { 195 | #[distribution(Uniform = Uniform::from(1..=6))] 196 | value: u8 197 | } 198 | 199 | let mut counter: HashMap = HashMap::new(); 200 | 201 | for _ in 0..6000 { 202 | let die: Die = rand::random(); 203 | *counter.entry(die.value).or_insert(0) += 1; 204 | } 205 | 206 | assert_eq!(counter.len(), 6); 207 | 208 | for i in 1..=6 { 209 | let count = counter[&i]; 210 | assert!(900 < count, "{}: {}", i, count); 211 | assert!(count < 1100, "{}: {}", i, count); 212 | } 213 | ``` 214 | 215 | ## Distribution caching 216 | 217 | In some cases, you may wish to cache a `Distribution` instance for reuse. Many 218 | distributions perform some initial calculations when constructed, and it can 219 | help performance to reuse existing distributions rather than recreate them 220 | every time a value is generated. `standard-dist` provides two ways to cache 221 | distributions: `static` and `once`. A `static` distribution is stored as a 222 | global static variable; this is the preferable option, but it requires the 223 | initializer to be usable in a `const` context. A `once` distribution is stored 224 | in a `once_cell::sync::OnceCell`; it is initialized the first time it's used, 225 | and then reused on subsequent invocations. 226 | 227 | In either case, a cache policy is specified by prefixing the type with `once` or 228 | `static`. The type must be specified in order to use a cache policy. 229 | 230 | ```rust 231 | use std::collections::HashMap; 232 | use std::time::{Instant, Duration}; 233 | use standard_dist::StandardDist; 234 | use rand::prelude::*; 235 | use rand::distributions::Uniform; 236 | 237 | #[derive(StandardDist)] 238 | struct Die { 239 | #[distribution(Uniform::from(1..=6))] 240 | value: u8 241 | } 242 | 243 | #[derive(StandardDist)] 244 | struct CachedDie { 245 | #[distribution(once Uniform = Uniform::from(1..=6))] 246 | value: u8 247 | } 248 | 249 | fn timed(task: impl FnOnce() -> T) -> (T, Duration) { 250 | let start = Instant::now(); 251 | (task(), start.elapsed()) 252 | } 253 | 254 | // Count the 6s 255 | let mut rng = StdRng::from_entropy(); 256 | 257 | let (count, plain_die_duration) = timed(|| (0..600000) 258 | .map(|_| rng.gen()) 259 | .filter(|&Die{ value }| value == 6) 260 | .count() 261 | ); 262 | 263 | assert!(90000 < count); 264 | assert!(count < 110000); 265 | 266 | let (count, cache_die_duration) = timed(|| (0..600000) 267 | .map(|_| rng.gen()) 268 | .filter(|&CachedDie{ value }| value == 6) 269 | .count() 270 | ); 271 | 272 | assert!(90000 < count); 273 | assert!(count < 110000); 274 | 275 | assert!( 276 | cache_die_duration < plain_die_duration, 277 | "cache: {:?}, plain: {:?}", 278 | cache_die_duration, 279 | plain_die_duration, 280 | ); 281 | ``` 282 | 283 | Note that, unless you're generating a huge quantity of random objects, using 284 | `cell` is likely a pessimization because of the upfront cost to initializing 285 | the cell. Make sure to benchmark your specific use case if performance is a 286 | concern. 287 | 288 | 289 | [`rand`]: https://docs.rs/rand/ 290 | [`Distribution`]: https://docs.rs/rand/latest/rand/distributions/trait.Distribution.html 291 | [`Standard`]: https://docs.rs/rand/latest/rand/distributions/struct.Standard.html 292 | [source of randomness]: https://docs.rs/rand/latest/rand/trait.Rng.html 293 | [`Rng::gen`]: https://docs.rs/rand/latest/rand/trait.Rng.html#method.gen 294 | */ 295 | use std::{collections::HashSet, iter}; 296 | 297 | use itertools::Itertools; 298 | use parse::ParseStream; 299 | use proc_macro::TokenStream; 300 | use proc_macro2::{Ident, Span, TokenStream as TokenStream2}; 301 | use quote::{quote, ToTokens}; 302 | use syn::{ 303 | parse, 304 | parse::{discouraged::Speculative, Parse}, 305 | parse_quote, 306 | spanned::Spanned, 307 | DeriveInput, Error, Expr, Field, Fields, LitInt, Token, Type, Variant, 308 | }; 309 | 310 | /// A particular field type, paired with the type of the distribution used 311 | /// to produce it. Used to create `where` bindings. 312 | #[derive(Debug, Clone, PartialEq, Eq, Hash)] 313 | struct FieldDistributionBinding<'a> { 314 | field_type: &'a Type, 315 | distribution_type: Type, 316 | } 317 | 318 | /// Given a list of fields (as from a struct or enum variant), return a list 319 | /// of all the types of those fields, paired with the associated distribution 320 | /// types. 321 | fn fields_types(fields: &Fields) -> impl Iterator> { 322 | fields.iter().filter_map(|field| { 323 | field_distribution(field) 324 | .map(|spec| { 325 | spec.container.map(|container| FieldDistributionBinding { 326 | field_type: &field.ty, 327 | distribution_type: container.ty, 328 | }) 329 | }) 330 | .transpose() 331 | }) 332 | } 333 | 334 | /// Given a type definition- a struct or enum- return an iterator over 335 | /// all the types of all the fields in that type, paired with the associated 336 | /// distribution types. 337 | fn item_subtypes( 338 | input: &DeriveInput, 339 | ) -> Box>> + '_> { 340 | match &input.data { 341 | syn::Data::Struct(data) => Box::new(fields_types(&data.fields)), 342 | syn::Data::Enum(data) => Box::new( 343 | data.variants 344 | .iter() 345 | .flat_map(|variant| fields_types(&variant.fields)), 346 | ), 347 | syn::Data::Union(_) => Box::new(iter::empty()), 348 | } 349 | } 350 | 351 | #[derive(Debug, Clone, Copy, PartialEq, Eq)] 352 | enum FieldDistributionStorage { 353 | Local, 354 | Once, 355 | Static, 356 | } 357 | 358 | impl Parse for FieldDistributionStorage { 359 | fn parse(input: ParseStream) -> syn::Result { 360 | use FieldDistributionStorage::*; 361 | 362 | input.step(|cursor| match cursor.ident() { 363 | Some((ident, tail)) if ident == "static" => Ok((Static, tail)), 364 | Some((ident, tail)) if ident == "once" => Ok((Once, tail)), 365 | _ => Ok((Local, *cursor)), 366 | }) 367 | } 368 | } 369 | 370 | #[derive(Debug, Clone)] 371 | struct FieldDistributionContainer { 372 | ty: Type, 373 | storage: FieldDistributionStorage, 374 | } 375 | 376 | #[derive(Debug, Clone)] 377 | struct FieldDistributionSpec { 378 | init: Expr, 379 | container: Option, 380 | } 381 | 382 | impl Parse for FieldDistributionSpec { 383 | fn parse(input: ParseStream) -> syn::Result { 384 | let storage: FieldDistributionStorage = input.parse()?; 385 | 386 | if storage == FieldDistributionStorage::Local { 387 | // There was no storage specifier. Try to parse `type =`, but 388 | // fall back to just an expression. 389 | let input_with_type = input.fork(); 390 | 391 | if let Ok(ty) = input_with_type.parse() { 392 | if let Ok(_eq) = input_with_type.parse::() { 393 | // We got "type =", so proceed unconditionally this way 394 | input.advance_to(&input_with_type); 395 | let original = input.fork(); 396 | let init = input.parse().map_err(|_| { 397 | Error::new(original.span(), "expected a distribution expression") 398 | })?; 399 | return Ok(FieldDistributionSpec { 400 | init, 401 | container: Some(FieldDistributionContainer { ty, storage }), 402 | }); 403 | } 404 | } 405 | 406 | let original = input.fork(); 407 | 408 | // Failed to parse "type =". Attempt to just parse the expression. 409 | input 410 | .parse() 411 | .map(|init| FieldDistributionSpec { 412 | init, 413 | container: None, 414 | }) 415 | .map_err(|_| Error::new(original.span(), "expected a distribution expression")) 416 | } else { 417 | // If we had a storage specifier, we now must have a type 418 | let ty = input 419 | .parse() 420 | .map_err(|_| Error::new(input.span(), "expected a distribution type"))?; 421 | let _equals: Token![=] = input.parse()?; 422 | let init = input 423 | .parse() 424 | .map_err(|_| Error::new(input.span(), "expected a distribution expression"))?; 425 | Ok(FieldDistributionSpec { 426 | init, 427 | container: Some(FieldDistributionContainer { ty, storage }), 428 | }) 429 | } 430 | } 431 | } 432 | 433 | /// Given a field, look at the #[distribution] attribute of the field to 434 | /// determine what distribution should be used. Returns the Standard 435 | /// distribution if there is no such attribute. The returned token stream 436 | /// should be an expression which can be passed to rng.sample. 437 | fn field_distribution(field: &Field) -> syn::Result { 438 | match field 439 | .attrs 440 | .iter() 441 | .find(|attr| attr.path.is_ident("distribution")) 442 | { 443 | None => Ok(FieldDistributionSpec { 444 | init: parse_quote! {::rand::distributions::Standard}, 445 | container: Some(FieldDistributionContainer { 446 | ty: parse_quote! {::rand::distributions::Standard}, 447 | storage: FieldDistributionStorage::Local, 448 | }), 449 | }), 450 | Some(attr) => attr.parse_args(), 451 | } 452 | } 453 | 454 | /// Given a list of fields, create a comma-separated series of initializers 455 | /// suited for initializing a type containing those fields. Return something 456 | /// resembling "field1: value1, field2: value2," for fields with names, and 457 | /// "value1, value2," for fields without names. 458 | /// 459 | /// The initializers are specifically the invocations of 460 | /// `rng.sample(distribution)`. 461 | fn field_inits<'a>( 462 | rng: &Ident, 463 | fields: impl Iterator, 464 | ) -> syn::Result { 465 | fields 466 | .map(|field| { 467 | let field_type = &field.ty; 468 | let distribution = field_distribution(&field)?; 469 | let (dist_ty, dist_init) = match distribution.container { 470 | None => (parse_quote! {_}, distribution.init), 471 | Some(container) => { 472 | let ty = container.ty; 473 | let init = distribution.init; 474 | 475 | match container.storage { 476 | FieldDistributionStorage::Local => (ty, init), 477 | FieldDistributionStorage::Once => ( 478 | parse_quote! {&'static #ty}, 479 | parse_quote! {{ 480 | static DISTRIBUTION: ::once_cell::sync::OnceCell<#ty> = 481 | ::once_cell::sync::OnceCell::new(); 482 | 483 | DISTRIBUTION.get_or_init(move || #init) 484 | }}, 485 | ), 486 | FieldDistributionStorage::Static => ( 487 | parse_quote! {&'static #ty}, 488 | parse_quote! {{ 489 | static DISTRIBUTION: #ty = #init; 490 | 491 | &DISTRIBUTION 492 | }}, 493 | ), 494 | } 495 | } 496 | }; 497 | 498 | let init = quote! { ::rand::Rng::sample::<#field_type, #dist_ty>(#rng, #dist_init), }; 499 | Ok(match &field.ident { 500 | Some(field_ident) => quote! { #field_ident: #init }, 501 | None => init, 502 | }) 503 | }) 504 | .collect() 505 | } 506 | 507 | /// Create a literal expression initializing a value of the given `type` 508 | /// consisting of the given fields. Used to create expressions to initialize 509 | /// structs and enum variants. 510 | fn init_value_of_type( 511 | type_path: TokenStream2, 512 | rng: &Ident, 513 | fields: &Fields, 514 | ) -> syn::Result { 515 | match fields { 516 | Fields::Named(fields) => { 517 | let field_inits = field_inits(rng, fields.named.iter())?; 518 | 519 | Ok(quote! { 520 | #type_path { 521 | #field_inits 522 | } 523 | }) 524 | } 525 | Fields::Unnamed(fields) => { 526 | let field_inits = field_inits(rng, fields.unnamed.iter())?; 527 | 528 | Ok(quote! { 529 | #type_path ( 530 | #field_inits 531 | ) 532 | }) 533 | } 534 | Fields::Unit => Ok(type_path), 535 | } 536 | } 537 | 538 | /// Look at the #[weight] attribute of an enum variant to determine what weight 539 | /// it should be given in random generation. Returns 1 if there is no such 540 | /// attribute, or an error if the attribute is malformed. 541 | fn enum_variant_weight(variant: &Variant) -> syn::Result { 542 | match variant 543 | .attrs 544 | .iter() 545 | .find(|attr| attr.path.is_ident("weight")) 546 | { 547 | None => Ok(1), 548 | Some(attr) => attr.parse_args::()?.base10_parse(), 549 | } 550 | } 551 | 552 | /// Similar to `try!`, this macro wraps a `syn::Result`, and converts the 553 | /// error to a compile error and returns it in the event of an error. 554 | macro_rules! syn_unwrap { 555 | ($input:expr) => { 556 | match ($input) { 557 | Ok(value) => value, 558 | Err(err @ syn::Error { .. }) => return err.into_compile_error().into(), 559 | } 560 | }; 561 | } 562 | 563 | #[proc_macro_derive(StandardDist, attributes(weight, distribution))] 564 | pub fn standard_dist(item: TokenStream) -> TokenStream { 565 | let input: DeriveInput = match parse(item) { 566 | Ok(input) => input, 567 | Err(err) => return err.into_compile_error().into(), 568 | }; 569 | 570 | let type_ident = &input.ident; 571 | let rng = Ident::new("rng", Span::mixed_site()); 572 | 573 | let sample_body = match &input.data { 574 | syn::Data::Struct(data) => syn_unwrap!(init_value_of_type( 575 | type_ident.to_token_stream(), 576 | &rng, 577 | &data.fields 578 | )), 579 | syn::Data::Enum(data) => { 580 | // The total weights that have been accumulated for all variants. 581 | let mut cumulative_weight = Some(0u64); 582 | 583 | // TODO: There's enough weird control flow and statefulness here 584 | // that it should probably be a plain for loop. The problem, 585 | // ironically, is that it's actually easier to use an iterator 586 | // chain, because we can use `?`. This should all be refactored 587 | // into a function returning a syn::Result. 588 | let match_arms = data 589 | .variants 590 | .iter() 591 | // For each variant, compute the weight. The weight is given 592 | // via a #[weight(10)] annotation, defaulting to 1. May return 593 | // an error for a malformed annotation. 594 | .map(|variant| enum_variant_weight(variant).map(|weight| (variant, weight))) 595 | // Skip variants with a weight of 0. 596 | .filter_ok(|&(_, weight)| weight != 0) 597 | // Create a match arm for each variant 598 | .map(|state| { 599 | let (variant, weight) = state?; 600 | 601 | // Process the cumulative weights. Compute the inclusive lower 602 | // and upper bounds for this variant, and update the cumulative 603 | // weight. 604 | let lower_bound = cumulative_weight.ok_or_else(|| { 605 | Error::new(variant.span(), "enum variant weight overflow") 606 | })?; 607 | let upper_bound = lower_bound.checked_add(weight - 1).ok_or_else(|| { 608 | Error::new(variant.span(), "enum variant weight overflow") 609 | })?; 610 | cumulative_weight = upper_bound.checked_add(1); 611 | 612 | // Create a match arm for each variant 613 | let variant_ident = &variant.ident; 614 | let variant_path = quote! {#type_ident::#variant_ident}; 615 | let gen_variant = init_value_of_type(variant_path, &rng, &variant.fields)?; 616 | let pattern = quote! {#lower_bound ..= #upper_bound}; 617 | Ok(quote! {#pattern => #gen_variant,}) 618 | }) 619 | .collect(); 620 | 621 | let match_arms: TokenStream2 = syn_unwrap!(match_arms); 622 | 623 | // In the likely event that we didn't use an entire u64's worth of 624 | // weights, create a trailing catch-all arm with an `unreachable` 625 | let trailing_arm = cumulative_weight.map(|cumulative_weight| { 626 | quote! { 627 | n => ::std::unreachable!( 628 | "The enum {} only has {} total weight, but the rng returned {}", 629 | ::std::stringify!(#type_ident), 630 | #cumulative_weight, 631 | n 632 | ), 633 | } 634 | }); 635 | 636 | // Create the expression that actually produces a random integer 637 | // which is used to randomly select a variant. 638 | let gen_variant_selector = match cumulative_weight { 639 | None => quote! { ::rand::Rng::gen(#rng) }, 640 | Some(0) => { 641 | return Error::new( 642 | input.span(), 643 | match data.variants.len() { 644 | 0 => "cannot derive StandardDist for empty enums", 645 | _ => "must have at least one variant with a nonzero weight", 646 | }, 647 | ) 648 | .into_compile_error() 649 | .into() 650 | } 651 | Some(upper_bound) => quote! { ::rand::Rng::gen_range(#rng, 0u64..#upper_bound) }, 652 | }; 653 | 654 | quote! { 655 | match #gen_variant_selector { 656 | #match_arms 657 | #trailing_arm 658 | } 659 | } 660 | } 661 | syn::Data::Union(..) => { 662 | return Error::new(input.span(), "cannot derive `StandardDist` on a union") 663 | .into_compile_error() 664 | .into() 665 | } 666 | }; 667 | 668 | let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl(); 669 | 670 | let where_clause = if !input.generics.params.is_empty() { 671 | let type_bindings: HashSet = 672 | syn_unwrap!(item_subtypes(&input).collect()); 673 | 674 | let type_bindings = type_bindings.iter().map( 675 | |FieldDistributionBinding { 676 | field_type, 677 | distribution_type, 678 | }| quote!( #distribution_type: ::rand::distributions::Distribution<#field_type> ), 679 | ); 680 | 681 | let type_bindings = type_bindings.chain( 682 | where_clause 683 | .into_iter() 684 | .flat_map(|clause| clause.predicates.iter().map(|pred| pred.to_token_stream())), 685 | ); 686 | 687 | quote! {where #(#type_bindings),*} 688 | } else { 689 | quote! {#where_clause} 690 | }; 691 | 692 | let distribution_impl = quote! { 693 | impl #impl_generics ::rand::distributions::Distribution<#type_ident #ty_generics> for ::rand::distributions::Standard 694 | #where_clause 695 | { 696 | fn sample(&self, #rng: &mut R) -> #type_ident #ty_generics { 697 | #sample_body 698 | } 699 | } 700 | }; 701 | 702 | distribution_impl.into() 703 | } 704 | -------------------------------------------------------------------------------- /tests/tests.rs: -------------------------------------------------------------------------------- 1 | use std::collections::HashMap; 2 | 3 | use itertools::Itertools; 4 | use rand::distributions::Uniform; 5 | use rand::prelude::*; 6 | use standard_dist::StandardDist; 7 | 8 | #[derive(Debug, Clone, Copy, PartialEq, Eq, StandardDist)] 9 | enum Coin { 10 | Heads, 11 | Tails, 12 | } 13 | 14 | #[derive(Debug, Clone, Copy, PartialEq, Eq, StandardDist)] 15 | struct Die { 16 | #[distribution(Uniform::new(0, N))] 17 | value: u32, 18 | } 19 | 20 | #[derive(Debug, Clone, Copy, StandardDist)] 21 | enum Fancy { 22 | Unit, 23 | 24 | Field(Coin), 25 | 26 | Pair(Coin, Die<6>), 27 | 28 | #[weight(3)] 29 | WeightedStruct { 30 | coin: Coin, 31 | d8: Die<8>, 32 | d12: Die<12>, 33 | 34 | #[distribution(once Uniform = Uniform::new(-1.0, 1.0))] 35 | float: f64, 36 | }, 37 | } 38 | 39 | #[test] 40 | fn test_fancy() { 41 | let mut rng = StdRng::from_entropy(); 42 | 43 | let mut d6_counts: HashMap = HashMap::new(); 44 | let mut d8_counts: HashMap = HashMap::new(); 45 | let mut d12_counts: HashMap = HashMap::new(); 46 | 47 | let mut heads_count = 0; 48 | let mut tails_count = 0; 49 | 50 | // There should be 50/50 weighted struct vs everything else 51 | let mut weighted_count = 0; 52 | 53 | for _ in 0..100000 { 54 | let fancy: Fancy = rng.gen(); 55 | 56 | match fancy { 57 | Fancy::Unit => {} 58 | Fancy::Field(coin) => match coin { 59 | Coin::Heads => heads_count += 1, 60 | Coin::Tails => tails_count += 1, 61 | }, 62 | Fancy::Pair(coin, d6) => { 63 | match coin { 64 | Coin::Heads => heads_count += 1, 65 | Coin::Tails => tails_count += 1, 66 | } 67 | *d6_counts.entry(d6.value).or_default() += 1; 68 | } 69 | Fancy::WeightedStruct { 70 | coin, 71 | d8, 72 | d12, 73 | float, 74 | } => { 75 | weighted_count += 1; 76 | match coin { 77 | Coin::Heads => heads_count += 1, 78 | Coin::Tails => tails_count += 1, 79 | } 80 | *d8_counts.entry(d8.value).or_default() += 1; 81 | *d12_counts.entry(d12.value).or_default() += 1; 82 | assert!(-1.0 <= float); 83 | assert!(float < 1.0); 84 | } 85 | } 86 | } 87 | 88 | // Heuristic: min == 90% of max at worst 89 | 90 | let unweighted_count = 100000 - weighted_count; 91 | let weight_ratio = weighted_count as f64 / unweighted_count as f64; 92 | assert!(0.9 < weight_ratio); 93 | assert!(weight_ratio < 1.1); 94 | 95 | let coin_ratio = heads_count as f64 / tails_count as f64; 96 | assert!(0.9 < coin_ratio); 97 | assert!(coin_ratio < 1.1); 98 | 99 | assert_eq!(d6_counts.len(), 6); 100 | assert_eq!(d8_counts.len(), 8); 101 | assert_eq!(d12_counts.len(), 12); 102 | 103 | for counts in &[d6_counts, d8_counts, d12_counts] { 104 | let (min, max) = counts.values().copied().minmax().into_option().unwrap(); 105 | let ratio = min as f64 / max as f64; 106 | assert!(0.9 < ratio); 107 | assert!(ratio <= 1.0); 108 | } 109 | } 110 | 111 | #[derive(Debug, Clone, StandardDist)] 112 | enum Generics { 113 | Unit, 114 | One(u32), 115 | Gen(T), 116 | Pair(T, U), 117 | Group { t: T, u: U, f: f64 }, 118 | } 119 | 120 | #[test] 121 | fn test_generic() { 122 | let _gen: Generics> = random(); 123 | // TODO: fill in tests. For now we're content that if it compiles, it 124 | // works. 125 | } 126 | --------------------------------------------------------------------------------