diff options
Diffstat (limited to 'gen_random_proc_macro')
| -rw-r--r-- | gen_random_proc_macro/Cargo.lock | 47 | ||||
| -rw-r--r-- | gen_random_proc_macro/Cargo.toml | 12 | ||||
| -rw-r--r-- | gen_random_proc_macro/src/lib.rs | 120 |
3 files changed, 179 insertions, 0 deletions
diff --git a/gen_random_proc_macro/Cargo.lock b/gen_random_proc_macro/Cargo.lock new file mode 100644 index 0000000..412ff2e --- /dev/null +++ b/gen_random_proc_macro/Cargo.lock @@ -0,0 +1,47 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +version = 3 + +[[package]] +name = "gen_random_proc_macro" +version = "0.1.0" +dependencies = [ + "proc-macro2", + "quote", + "syn", +] + +[[package]] +name = "proc-macro2" +version = "1.0.47" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "5ea3d908b0e36316caf9e9e2c4625cdde190a7e6f440d794667ed17a1855e725" +dependencies = [ + "unicode-ident", +] + +[[package]] +name = "quote" +version = "1.0.21" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "bbe448f377a7d6961e30f5955f9b8d106c3f5e449d493ee1b125c1d43c2b5179" +dependencies = [ + "proc-macro2", +] + +[[package]] +name = "syn" +version = "1.0.105" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "60b9b43d45702de4c839cb9b51d9f529c5dd26a4aff255b42b1ebc03e88ee908" +dependencies = [ + "proc-macro2", + "quote", + "unicode-ident", +] + +[[package]] +name = "unicode-ident" +version = "1.0.5" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "6ceab39d59e4c9499d4e5a8ee0e2735b891bb7308ac83dfb4e80cad195c9f6f3" diff --git a/gen_random_proc_macro/Cargo.toml b/gen_random_proc_macro/Cargo.toml new file mode 100644 index 0000000..bcf05ce --- /dev/null +++ b/gen_random_proc_macro/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "gen_random_proc_macro" +version = "0.1.0" +edition = "2021" + +[lib] +proc-macro = true + +[dependencies] +proc-macro2 = "1.0" +quote = "1.0" +syn = "1.0" diff --git a/gen_random_proc_macro/src/lib.rs b/gen_random_proc_macro/src/lib.rs new file mode 100644 index 0000000..e621a76 --- /dev/null +++ b/gen_random_proc_macro/src/lib.rs @@ -0,0 +1,120 @@ +extern crate quote; +extern crate proc_macro2; +extern crate syn; + +use proc_macro::{TokenStream, TokenTree::{self, Punct, Literal}}; +use quote::quote; + +#[proc_macro_derive(GenRandom, attributes(prob))] +pub fn gen_random_derive(input: TokenStream) -> TokenStream { + // Construct a representation of Rust code as a syntax tree + // that we can manipulate + let ast = syn::parse(input).unwrap(); + // Build the trait implementation + impl_gen_random(&ast) +} + + +fn impl_gen_random(ast: &syn::DeriveInput) -> TokenStream { + let name = &ast.ident; + match &ast.data { + syn::Data::Enum(enumeration) => { + let variants = &enumeration.variants; + let epsilon: f64 = 1e-9; + let one_minus_epsilon = 1.0 - epsilon; + let mut function_body = quote! { + let mut variant: f64 = rng.gen_range(0.0..#one_minus_epsilon); + }; + + let mut test_variant = one_minus_epsilon; + + // parse enum fields + for variant in variants.iter() { + let probability: f64 = { + let attr = variant.attrs.iter().find(|a| { + let path = &a.path; + if let Some(ident) = path.get_ident() { + ident == "prob" + } else { + false + } + }); + let Some(attr) = attr else { + panic!("Variant {} has no probability", variant.ident) + }; + let tokens: TokenStream = attr.tokens.clone().into(); + let tokens: Vec<TokenTree> = tokens.into_iter().collect(); + if tokens.len() != 2 { + panic!("Expected prob = <floating-point number>"); + } + match &tokens[0] { + Punct(equals) if equals.as_char() == '=' => {} + _ => panic!("Expected = after prob attribute"), + }; + + let Literal(literal) = &tokens[1] else { + panic!("Bad number for prob attribute."); + }; + literal.to_string().parse().expect("Bad number for prob attribute") + }; + + let name = &variant.ident; + + + let mut variant_arguments = quote! {}; + for field in variant.fields.iter() { + if let Some(name) = &field.ident { + variant_arguments.extend(quote! {#name: }); + } + let ty = &field.ty; + variant_arguments.extend(quote! { <#ty as GenRandom>::gen_random(rng), }); + } + + // surround the arguments with either () or {} brackets + let constructor_group = match variant.fields { + syn::Fields::Named(_) => { + Some(proc_macro2::Group::new( + proc_macro2::Delimiter::Brace, + variant_arguments + )) + }, + syn::Fields::Unnamed(_) => { + Some(proc_macro2::Group::new( + proc_macro2::Delimiter::Parenthesis, + variant_arguments + )) + }, + syn::Fields::Unit => None, + }; + + function_body.extend(quote! { + variant -= #probability; + if variant <= 0.0 { return Self::#name #constructor_group; } + }); + test_variant -= probability; + + + } + + if test_variant >= 0.0 || test_variant < -2.0 * epsilon { + panic!("Probabilities for enum do not add up to 1 (final test_variant = {test_variant})."); + } + + function_body.extend(quote! { + panic!("RNG returned value outside of range.") + }); + + let gen = quote! { + impl GenRandom for #name { + fn gen_random(rng: &mut impl rand::Rng) -> Self { + #function_body + } + } + }; + //println!("{gen}"); + gen.into() + }, + _ => panic!("derive(GenRandom) can currently only be applied to enums."), + } +} + |