Implement polymorphic function macro with deterministic selection; add README, LICENSE, and CI workflow. Update example project and dependencies.

Author: Eduardo Contin

.github/workflows/ci.yml

@@ -0,0 +1,60 @@
+name: Rust CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - name: Run tests
+        run: cargo test --verbose
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy
+      - uses: Swatinem/rust-cache@v2
+      - name: Clippy check
+        run: cargo clippy -- -D warnings
+
+  formatting:
+    name: Formatting
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+      - name: Check formatting
+        run: cargo fmt --all -- --check
+
+  publish:
+    name: Publish
+    needs: [test, clippy, formatting]
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/v')
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - name: Login to crates.io
+        run: cargo login ${{ secrets.CRATES_IO_TOKEN }}
+      - name: Publish
+        run: |
+          cd polymorphic_fn
+          cargo publish 

.gitignore

@@ -1 +1,2 @@
-*/target
+*/target
+.cursor/rules/riper-5.mdc

LICENSE

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+MIT License
+
+Copyright (c) 2023 Your Name
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE. 

README.md

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+# polymorphic_fn
+
+[![Crates.io](https://img.shields.io/crates/v/polymorphic_fn.svg)](https://crates.io/crates/polymorphic_fn)
+[![Documentation](https://docs.rs/polymorphic_fn/badge.svg)](https://docs.rs/polymorphic_fn)
+[![MIT License](https://img.shields.io/badge/license-MIT-blue.svg)](LICENSE)
+
+A Rust procedural macro that enables functions with multiple implementations, where one is deterministically selected at compile-time.
+
+## Features
+
+- Define multiple function implementations in a single macro call
+- One implementation is deterministically selected at compile-time
+- Unused implementations are entirely removed from the binary
+- Selection is based on function name, build timestamp, and other factors
+- Useful for A/B testing, feature comparison, and binary size optimization
+
+## Installation
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+polymorphic_fn = "0.1.0"
+```
+
+## Usage
+
+### Basic Example
+
+```rust
+use polymorphic_fn::polymorphic_fn;
+
+polymorphic_fn! {
+    pub fn calculate(x: i32) -> i32 {
+        { x + 1 },         // Implementation 1
+        { x * 2 },         // Implementation 2
+        { x * x }          // Implementation 3
+    }
+}
+
+fn main() {
+    let result = calculate(5);
+    println!("Result: {}", result); // Will print result from one of the implementations
+}
+```
+
+### Use Cases
+
+#### Binary Size Optimization
+
+```rust
+use polymorphic_fn::polymorphic_fn;
+
+// Define alternative implementations with different size characteristics
+fn small_implementation(data: &[u8]) -> u64 {
+    // Simple, small implementation
+    data.iter().map(|&b| b as u64).sum()
+}
+
+fn large_implementation(data: &[u8]) -> u64 {
+    // Complex implementation with more features but larger code size
+    // (e.g., includes optimizations, debug code, etc.)
+    static LARGE_DATA: [u8; 1_000_000] = [0; 1_000_000];
+    data.iter().zip(LARGE_DATA.iter())
+        .map(|(&a, &b)| (a as u64) * (b as u64 + 1))
+        .sum()
+}
+
+polymorphic_fn! {
+    pub fn process_data(data: &[u8]) -> u64 {
+        { small_implementation(data) },
+        { large_implementation(data) }
+    }
+}
+```
+
+#### Implementation A/B Testing
+
+```rust
+use polymorphic_fn::polymorphic_fn;
+
+polymorphic_fn! {
+    pub fn sort_algorithm<T: Ord + Copy>(data: &mut [T]) {
+        { 
+            // Implementation 1: Quick sort
+            data.sort_unstable();
+        },
+        { 
+            // Implementation 2: Insertion sort
+            for i in 1..data.len() {
+                let mut j = i;
+                while j > 0 && data[j-1] > data[j] {
+                    data.swap(j-1, j);
+                    j -= 1;
+                }
+            }
+        }
+    }
+}
+```
+
+## How It Works
+
+The `polymorphic_fn` macro uses compile-time hashing to deterministically select one implementation from the provided alternatives. The selection is based on:
+
+1. The function name
+2. Build timestamp
+3. Package name and version
+4. Target architecture and profile
+5. A build counter that increments on each build
+
+This ensures that the selection is consistent for a given build but can change between builds, allowing for different implementations to be tested over time.
+
+## Controlling Selection
+
+To force a rebuild and potentially get a different implementation selected, you can:
+
+1. Use a build script with `cargo:rerun-if-changed=nonexistent-file` to ensure the build script runs every time
+2. Set the `FORCE_REBUILD` environment variable before building
+3. Increment a build counter in your build script
+
+## License
+
+This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details. 

example/Cargo.lock

@@ -2,6 +2,7 @@
 name = "example"
 version = "0.1.0"
 edition = "2021"
+build = "build.rs"
 
 [dependencies]
 polymorphic_fn = { path = "../polymorphic_fn" }