diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..23ba550
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,32 @@
+version: "3.9"
+services:
+rust-dev:
+build:
+context: .
+dockerfile: docker/Dockerfile.rust-dev
+volumes:
+- ./:/work
+working_dir: /work
+command: bash -lc "cargo test --release"
+
+
+wasm:
+build:
+context: .
+dockerfile: docker/Dockerfile.wasm
+volumes:
+- ./:/work
+working_dir: /work
+command: bash -lc "make wasm && python3 -m http.server -d bindings/wasm/pkg 8000"
+ports:
+- "8000:8000"
+
+
+python:
+build:
+context: .
+dockerfile: docker/Dockerfile.rust-dev
+volumes:
+- ./:/work
+working_dir: /work
+command: bash -lc "make py && python -c 'from symreg_rs import PySymbolicRegressor as SR; print(SR().fit_predict([[0.0],[1.0]],[0.0,1.0]))'"
diff --git a/.gitignore b/.gitignore
index da7e412..6504a95 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,229 +1,10 @@
-# ---> Rust
-# Generated by Cargo
-# will have compiled files and executables
-debug/
 target/
-
-# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
-# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
-Cargo.lock
-
-# These are backup files generated by rustfmt
-**/*.rs.bk
-
-# MSVC Windows builds of rustc generate these, which store debugging information
-*.pdb
-
-# ---> Emacs
-# -*- mode: gitignore; -*-
-*~
-\#*\#
-/.emacs.desktop
-/.emacs.desktop.lock
-*.elc
-auto-save-list
-tramp
-.\#*
-
-# Org-mode
-.org-id-locations
-*_archive
-
-# flymake-mode
-*_flymake.*
-
-# eshell files
-/eshell/history
-/eshell/lastdir
-
-# elpa packages
-/elpa/
-
-# reftex files
-*.rel
-
-# AUCTeX auto folder
-/auto/
-
-# cask packages
-.cask/
-dist/
-
-# Flycheck
-flycheck_*.el
-
-# server auth directory
-/server/
-
-# projectiles files
-.projectile
-
-# directory configuration
-.dir-locals.el
-
-# network security
-/network-security.data
-
-
-# ---> Python
-# Byte-compiled / optimized / DLL files
+**/*.pyc
 __pycache__/
-*.py[cod]
-*$py.class
-
-# C extensions
-*.so
-
-# Distribution / packaging
-.Python
-build/
-develop-eggs/
-dist/
-downloads/
-eggs/
-.eggs/
-lib/
-lib64/
-parts/
-sdist/
-var/
-wheels/
-share/python-wheels/
-*.egg-info/
-.installed.cfg
-*.egg
-MANIFEST
-
-# PyInstaller
-#  Usually these files are written by a python script from a template
-#  before PyInstaller builds the exe, so as to inject date/other infos into it.
-*.manifest
-*.spec
-
-# Installer logs
-pip-log.txt
-pip-delete-this-directory.txt
-
-# Unit test / coverage reports
-htmlcov/
-.tox/
-.nox/
-.coverage
-.coverage.*
-.cache
-nosetests.xml
-coverage.xml
-*.cover
-*.py,cover
-.hypothesis/
-.pytest_cache/
-cover/
-
-# Translations
-*.mo
-*.pot
-
-# Django stuff:
-*.log
-local_settings.py
-db.sqlite3
-db.sqlite3-journal
-
-# Flask stuff:
-instance/
-.webassets-cache
-
-# Scrapy stuff:
-.scrapy
-
-# Sphinx documentation
-docs/_build/
-
-# PyBuilder
-.pybuilder/
-target/
-
-# Jupyter Notebook
-.ipynb_checkpoints
-
-# IPython
-profile_default/
-ipython_config.py
-
-# pyenv
-#   For a library or package, you might want to ignore these files since the code is
-#   intended to run in multiple environments; otherwise, check them in:
-# .python-version
-
-# pipenv
-#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
-#   However, in case of collaboration, if having platform-specific dependencies or dependencies
-#   having no cross-platform support, pipenv may install dependencies that don't work, or not
-#   install all needed dependencies.
-#Pipfile.lock
-
-# poetry
-#   Similar to Pipfile.lock, it is generally recommended to include poetry.lock in version control.
-#   This is especially recommended for binary packages to ensure reproducibility, and is more
-#   commonly ignored for libraries.
-#   https://python-poetry.org/docs/basic-usage/#commit-your-poetrylock-file-to-version-control
-#poetry.lock
-
-# pdm
-#   Similar to Pipfile.lock, it is generally recommended to include pdm.lock in version control.
-#pdm.lock
-#   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
-#   in version control.
-#   https://pdm.fming.dev/#use-with-ide
-.pdm.toml
-
-# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
-__pypackages__/
-
-# Celery stuff
-celerybeat-schedule
-celerybeat.pid
-
-# SageMath parsed files
-*.sage.py
-
-# Environments
-.env
-.venv
-env/
-venv/
-ENV/
-env.bak/
-venv.bak/
-
-# Spyder project settings
-.spyderproject
-.spyproject
-
-# Rope project settings
-.ropeproject
-
-# mkdocs documentation
-/site
-
-# mypy
-.mypy_cache/
-.dmypy.json
-dmypy.json
-
-# Pyre type checker
-.pyre/
-
-# pytype static type analyzer
-.pytype/
-
-# Cython debug symbols
-cython_debug/
-
-# PyCharm
-#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
-#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
-#  and can be added to the global gitignore or merged into this file.  For a more nuclear
-#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
-#.idea/
-
+*.pyo
+.vscode/
+.idea/
+.DS_Store
+bindings/python/target/
+bindings/python/*.egg-info/
+bindings/wasm/pkg/
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..1dd11e9
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,55 @@
+[package]
+name = "symreg-rs"
+version = "0.1.0"
+edition = "2021"
+license = "Apache-2.0"
+description = "Fast, extensible symbolic regression in Rust with Python bindings and WASM target"
+repository = "https://example.org/your/repo"
+
+
+[lib]
+name = "symreg_rs"
+crate-type = ["rlib", "cdylib"]
+
+
+[features]
+default = ["simd"]
+simd = []
+python = ["pyo3/extension-module", "pyo3/macros"]
+wasm = ["wasm-bindgen"]
+
+
+[dependencies]
+rand = "0.8"
+rand_distr = "0.4"
+smallvec = "1"
+bitflags = "2"
+thiserror = "1"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+rayon = "1"
+ordered-float = "4"
+
+
+# algebra & optimization
+nalgebra = { version = "0.33", default-features = false, features=["std"] }
+argmin = { version = "0.8", optional = true }
+
+
+# optional rewriting via e-graphs
+egg = { version = "0.9", optional = true }
+
+
+# bindings
+pyo3 = { version = "0.21", optional = true, features=["abi3", "abi3-py38"] }
+wasm-bindgen = { version = "0.2", optional = true }
+
+
+[dev-dependencies]
+criterion = "0.5"
+
+
+[profile.release]
+lto = true
+codegen-units = 1
+opt-level = 3
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..bc04d86
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,38 @@
+.PHONY: build test bench fmt lint py sdist wheel wasm demo
+
+
+build:
+cargo build --release
+
+
+test:
+cargo test --all --release
+
+
+bench:
+cargo bench
+
+
+fmt:
+cargo fmt --all
+cargo clippy --all-targets --all-features -- -D warnings
+
+
+py:
+maturin develop -m bindings/python/pyproject.toml
+
+
+sdist:
+maturin sdist -m bindings/python/pyproject.toml
+
+
+wheel:
+maturin build -m bindings/python/pyproject.toml --release
+
+
+wasm:
+wasm-pack build bindings/wasm --target web --release
+
+
+demo:
+python3 -m http.server -d bindings/wasm/pkg 8000
diff --git a/README.md b/README.md
index 2e0a05d..c3d3a23 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,68 @@
 # sr-rs
 
 SR-RS: A portable symbolic regression engine in Rust, patterned after Cranmer's SymbolicRegression.jl.
+
+**Rust symbolic regression** with:
+
+
+- 🦀 **Core in Rust** (fast evaluators, SIMD where available)
+- 🐍 **Python bindings** (PyO3, scikit-learn-style API)
+- 🌐 **WASM target** (`wasm-bindgen`, in-browser demo)
+- ♻️ **Rewrite-based simplification** (optional `egg` integration)
+- 🎯 Multi-objective search (error vs. complexity), constant-fitting, protected operators, and export to SymPy/LaTeX
+
+
+## Quick start
+
+
+### Native (Rust)
+```bash
+cargo run --example quickstart
+
+
+Python
+# inside container or host with Rust toolchain
+make py
+python -c "from symreg_rs import SymbolicRegressor; print(SymbolicRegressor().fit_predict([[0.0],[1.0]], [0.0,1.0]))"
+WebAssembly demo
+make wasm && make demo
+# open http://localhost:8000/index.html
+Design highlights
+
+Expression AST with typed operations and arity checks
+
+Fast vectorized evaluator (feature simd)
+
+GP loop with tournament selection, variation (mutate/crossover), and Pareto archiving
+
+Constant optimization via LM/Argmin (optional)
+
+Simplification via identities + (optional) egg equality saturation
+
+See docs/DESIGN.md and docs/PORTING.md for details and porting guidance.
+
+9) Usage snippets
+Rust
+use symreg_rs::{GpConfig, SymbolicRegressor};
+let x = vec![vec![0.0], vec![1.0]];
+let y = vec![0.0, 1.0];
+let sr = SymbolicRegressor::default();
+let expr = sr.fit(&x, &y);
+Python
+from symreg_rs import PySymbolicRegressor as SR
+sr = SR(pop_size=256, gens=20, num_vars=1)
+preds = sr.fit_predict([[0.0],[1.0]],[0.0,1.0])
+10) Next steps (recommended)
+
+Wire up constant fitting (Argmin LM) in fitness.rs.
+
+Add exporters: to SymPy string and LaTeX.
+
+Implement subtree crossover/mutation and depth/size limits.
+
+Add vectorized evaluator (std::simd) + rayon parallelism.
+
+Optional: integrate egg for global simplification.
+
+This scaffold should compile with minor tweaks (crate names/versions). From here, we can iterate on the porting branch to reach feature parity with your preferred SR baseline.
+
diff --git a/bindings/python/pyproject.toml b/bindings/python/pyproject.toml
new file mode 100644
index 0000000..7b657c1
--- /dev/null
+++ b/bindings/python/pyproject.toml
@@ -0,0 +1,20 @@
+[build-system]
+requires = ["maturin>=1.4"]
+build-backend = "maturin"
+
+
+[project]
+name = "symreg-rs"
+version = "0.1.0"
+description = "Rust symbolic regression with Python bindings"
+authors = [{name="Your Name", email="you@example.com"}]
+requires-python = ">=3.8"
+classifiers = [
+"Programming Language :: Python :: 3",
+"Programming Language :: Rust",
+]
+
+
+[tool.maturin]
+features = ["python"]
+module-name = "symreg_rs"
diff --git a/bindings/python/src/lib.rs b/bindings/python/src/lib.rs
new file mode 100644
index 0000000..fd19eda
--- /dev/null
+++ b/bindings/python/src/lib.rs
@@ -0,0 +1,33 @@
+use pyo3::prelude::*;
+use symreg_rs::{GpConfig, SymbolicRegressor};
+
+
+#[pyclass]
+struct PySymbolicRegressor { inner: SymbolicRegressor }
+
+
+#[pymethods]
+impl PySymbolicRegressor {
+#[new]
+fn new(pop_size: Option<usize>, gens: Option<usize>, num_vars: Option<usize>) -> Self {
+let mut cfg = GpConfig::default();
+if let Some(v) = pop_size { cfg.pop_size = v; }
+if let Some(v) = gens { cfg.gens = v; }
+if let Some(v) = num_vars { cfg.num_vars = v; }
+Self { inner: SymbolicRegressor::new(cfg) }
+}
+
+
+fn fit_predict(&self, x: Vec<Vec<f64>>, y: Vec<f64>, predict_x: Option<Vec<Vec<f64>>>) -> PyResult<Vec<f64>> {
+let expr = self.inner.fit(&x, &y);
+let px = predict_x.unwrap_or(x);
+Ok(px.iter().map(|row| symreg_rs::eval::eval_expr(&expr, row)).collect())
+}
+}
+
+
+#[pymodule]
+fn symreg_rs(_py: Python, m: &PyModule) -> PyResult<()> {
+m.add_class::<PySymbolicRegressor>()?;
+Ok(())
+}
diff --git a/bindings/wasm/index.html b/bindings/wasm/index.html
new file mode 100644
index 0000000..2b8e08e
--- /dev/null
+++ b/bindings/wasm/index.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head><meta charset="utf-8"><title>symreg-rs WASM demo</title></head>
+<body>
+<h1>symreg-rs (WASM)</h1>
+<button id="run">Run demo</button>
+<pre id="out"></pre>
+<script type="module">
+import init, { fit_mse } from './pkg/symreg_rs_wasm.js';
+await init();
+document.getElementById('run').onclick = () => {
+const xs = []; const ys = [];
+for (let i=0;i<50;i++){ const v=i/10; xs.push(v); ys.push(Math.sin(v)); }
+const preds = fit_mse(xs, 50, 1, ys, 10);
+document.getElementById('out').textContent = JSON.stringify(preds.slice(0,10), null, 2);
+};
+</script>
+</body>
+</html>
diff --git a/bindings/wasm/package.json b/bindings/wasm/package.json
new file mode 100644
index 0000000..a150cd8
--- /dev/null
+++ b/bindings/wasm/package.json
@@ -0,0 +1,8 @@
+{
+"name": "symreg-rs-wasm",
+"version": "0.1.0",
+"scripts": {
+"build": "wasm-pack build --target web --release",
+"serve": "python3 -m http.server -d pkg 8000"
+}
+}
diff --git a/bindings/wasm/src/lib.rs b/bindings/wasm/src/lib.rs
new file mode 100644
index 0000000..b55cce5
--- /dev/null
+++ b/bindings/wasm/src/lib.rs
@@ -0,0 +1,15 @@
+use wasm_bindgen::prelude::*;
+use symreg_rs::{GpConfig, SymbolicRegressor};
+
+
+#[wasm_bindgen]
+pub fn fit_mse(x: Vec<f64>, n_rows: usize, n_cols: usize, y: Vec<f64>, gens: usize) -> Vec<f64> {
+let mut rows = Vec::with_capacity(n_rows);
+for r in 0..n_rows {
+let start = r*n_cols; rows.push(x[start..start+n_cols].to_vec());
+}
+let cfg = GpConfig { gens, num_vars: n_cols, ..Default::default() };
+let sr = SymbolicRegressor::new(cfg);
+let expr = sr.fit(&rows, &y);
+rows.iter().map(|row| symreg_rs::eval::eval_expr(&expr, row)).collect()
+}
diff --git a/docker-compose.yml b/docker-compose.yml
new file mode 100644
index 0000000..23ba550
--- /dev/null
+++ b/docker-compose.yml
@@ -0,0 +1,32 @@
+version: "3.9"
+services:
+rust-dev:
+build:
+context: .
+dockerfile: docker/Dockerfile.rust-dev
+volumes:
+- ./:/work
+working_dir: /work
+command: bash -lc "cargo test --release"
+
+
+wasm:
+build:
+context: .
+dockerfile: docker/Dockerfile.wasm
+volumes:
+- ./:/work
+working_dir: /work
+command: bash -lc "make wasm && python3 -m http.server -d bindings/wasm/pkg 8000"
+ports:
+- "8000:8000"
+
+
+python:
+build:
+context: .
+dockerfile: docker/Dockerfile.rust-dev
+volumes:
+- ./:/work
+working_dir: /work
+command: bash -lc "make py && python -c 'from symreg_rs import PySymbolicRegressor as SR; print(SR().fit_predict([[0.0],[1.0]],[0.0,1.0]))'"
diff --git a/docker/Dockerfile.python b/docker/Dockerfile.python
new file mode 100644
index 0000000..18414d5
--- /dev/null
+++ b/docker/Dockerfile.python
@@ -0,0 +1,5 @@
+FROM python:3.11-slim
+RUN apt-get update && apt-get install -y build-essential python3-dev && rm -rf /var/lib/apt/lists/*
+# wheel build happens via maturin in rust-dev; this image is for runtime
+RUN pip install numpy
+WORKDIR /app
diff --git a/docker/Dockerfile.rust-dev b/docker/Dockerfile.rust-dev
new file mode 100644
index 0000000..0b120f0
--- /dev/null
+++ b/docker/Dockerfile.rust-dev
@@ -0,0 +1,4 @@
+FROM rust:1.80
+RUN apt-get update && apt-get install -y python3 python3-pip pkg-config libssl-dev && rm -rf /var/lib/apt/lists/*
+RUN pip3 install maturin wasm-pack
+WORKDIR /work
diff --git a/docker/Dockerfile.wasm b/docker/Dockerfile.wasm
new file mode 100644
index 0000000..41dd02a
--- /dev/null
+++ b/docker/Dockerfile.wasm
@@ -0,0 +1,3 @@
+FROM rust:1.80
+RUN cargo install wasm-pack
+WORKDIR /work
diff --git a/docker/entrypoints/python-build.sh b/docker/entrypoints/python-build.sh
new file mode 100644
index 0000000..16897f2
--- /dev/null
+++ b/docker/entrypoints/python-build.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+make wheel
+exec "$@"
diff --git a/docker/entrypoints/rust-dev.sh b/docker/entrypoints/rust-dev.sh
new file mode 100644
index 0000000..a45dc6a
--- /dev/null
+++ b/docker/entrypoints/rust-dev.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+cargo build --release
+exec "$@"
diff --git a/docs/BENCHMARK.md b/docs/BENCHMARK.md
new file mode 100644
index 0000000..db1f150
--- /dev/null
+++ b/docs/BENCHMARK.md
@@ -0,0 +1,29 @@
+# BENCHMARKS
+
+
+- Use `criterion` for microbenchmarks (eval throughput).
+- Dataset-level timing: fit to Friedman1 and report wall-clock and MSE.
+- Compare feature toggles: scalar vs SIMD, parallel vs single-thread.
+
+
+
+---
+
+
+## 8) Branching model (with a `porting` branch)
+
+
+- `main`: stable, tagged releases.
+- `develop`: integration of ready features.
+- `porting`: **all work specific to parity with SymbolicRegression.jl** (feature-by-feature ports, benchmarks, notes). Merge into `develop` via PRs when each slice reaches MVP.
+- Per-feature branches from `porting` (e.g., `porting/const-fitting`, `porting/egg-rewrites`).
+
+
+**Initial commands:**
+```bash
+git init
+git checkout -b main
+git add . && git commit -m "feat: repo scaffold"
+git checkout -b develop
+git checkout -b porting
+
diff --git a/docs/DESIGN.md b/docs/DESIGN.md
new file mode 100644
index 0000000..51174be
--- /dev/null
+++ b/docs/DESIGN.md
@@ -0,0 +1,25 @@
+# DESIGN
+
+
+## Goals
+- Fast core with predictable performance (no runtime JIT)
+- Clean APIs for Python and Web
+- Extensibility: pluggable operators, fitness terms, search strategies
+
+
+## Key components
+- AST (`ast.rs`), evaluator (`eval.rs`), operators (`ops.rs`)
+- Fitness metrics (`fitness.rs`), GP algorithm (`gp.rs`)
+- Simplification (`simplify/`), utilities (`utils.rs`)
+
+
+## Error/Complexity tradeoff
+- Use bi-objective selection or scalarized cost; Pareto archive maintained per generation.
+
+
+## Safety
+- Protected operators for division/log; numeric guards where needed.
+
+
+## Determinism
+- Seeded RNG exposed in configs for reproducible runs.
diff --git a/docs/PORTING.md b/docs/PORTING.md
new file mode 100644
index 0000000..8f2e876
--- /dev/null
+++ b/docs/PORTING.md
@@ -0,0 +1,42 @@
+# Porting plan (from SymbolicRegression.jl concepts)
+
+
+This document maps major features/design choices to Rust equivalents and notes feasibility.
+
+
+## Search & representation
+- **Representation:** tree/graph AST with typed ops. Rust enums for ops and nodes. Feasible (done in MVP).
+- **Search:** GP with tournament selection + crossover/mutation, plus Pareto archiving. Extensible to age-fitness, lexicase.
+- **Constants:** LM/variable projection via `argmin`/`nalgebra`. Start with LM; later add autodiff for local gradients.
+
+
+## Evaluation performance
+- **Julia’s fused loops & SIMD:** replicate with `std::simd` and hand-rolled evaluators. Bench and specialize hot ops.
+- **Parallelism:** use `rayon` for population eval; thread support optional in WASM (SharedArrayBuffer route).
+
+
+## Simplification & pruning
+- **Local rules:** identities (e.g., `x+0→x`, `x*1→x`, `sin(0)→0`).
+- **Global rewriting:** integrate `egg` as optional feature for equality saturation + cost-based extraction.
+
+
+## Multi-objective
+- Maintain Pareto front on (error, complexity). Provide knobs for complexity penalty and max size/depth.
+
+
+## Export & interop
+- **Python:** PyO3 module `symreg_rs` with sklearn-like API (`fit`, `predict`, `score`).
+- **WASM:** thin bindgen façade for browser demos; avoid heavy deps.
+- **SymPy/LaTeX:** stringifier to SymPy code, plus LaTeX pretty-printing.
+
+
+## Test & benchmark
+- Reuse standard SRBench datasets where licensing permits; include Friedman1 synthetic.
+- Add criterion benches for evaluator and variation operators.
+
+
+## Milestones
+1. MVP (this scaffold): scalar eval, GP loop, Python & WASM hello world.
+2. Vectorized eval + `rayon` parallel pop eval; constant fitting.
+3. Simplifier + export; sklearn-compatible estimator.
+4. E-graph integration; advanced search strategies; docs + notebooks.
diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
new file mode 100644
index 0000000..4c0cc9e
--- /dev/null
+++ b/docs/ROADMAP.md
@@ -0,0 +1,11 @@
+# ROADMAP
+
+
+- [ ] SIMD evaluator
+- [ ] Parallel pop evaluation (rayon)
+- [ ] LM constant fitting
+- [ ] SymPy/LaTeX exporters
+- [ ] sklearn API parity (fit/predict/score, get_params/set_params)
+- [ ] E-graph simplification (egg)
+- [ ] Web demo with worker + shared memory
+- [ ] SRBench harness integration
diff --git a/examples/quickstart.rs b/examples/quickstart.rs
new file mode 100644
index 0000000..c72758f
--- /dev/null
+++ b/examples/quickstart.rs
@@ -0,0 +1,11 @@
+use symreg_rs::{GpConfig, SymbolicRegressor};
+
+
+fn main() {
+let x: Vec<Vec<f64>> = (0..50).map(|i| vec![i as f64 / 10.0]).collect();
+let y: Vec<f64> = x.iter().map(|v| v[0].sin()).collect();
+let cfg = GpConfig { num_vars: 1, gens: 10, ..Default::default() };
+let sr = SymbolicRegressor::new(cfg);
+let expr = sr.fit(&x, &y);
+println!("best expr nodes={}, root={}", expr.nodes.len(), expr.root);
+}
diff --git a/src/ast.rs b/src/ast.rs
new file mode 100644
index 0000000..2835f46
--- /dev/null
+++ b/src/ast.rs
@@ -0,0 +1,34 @@
+use serde::{Deserialize, Serialize};
+
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Hash)]
+pub enum Op {
+Add, Sub, Mul, Div, Sin, Cos, Exp, Log,
+// extendable: Tan, Abs, Pow, etc.
+}
+
+
+impl Op {
+pub fn arity(&self) -> usize {
+use Op::*;
+match self {
+Add | Sub | Mul | Div => 2,
+Sin | Cos | Exp | Log => 1,
+}
+}
+}
+
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum Node {
+Var(usize),
+Const(f64),
+Call(Op, smallvec::SmallVec<[usize; 4]>), // children indices
+}
+
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct Expr {
+pub nodes: Vec<Node>,
+pub root: usize,
+}
diff --git a/src/eval.rs b/src/eval.rs
new file mode 100644
index 0000000..d4c7e78
--- /dev/null
+++ b/src/eval.rs
@@ -0,0 +1,25 @@
+use crate::ast::{Expr, Node, Op};
+use crate::ops::{apply_unary, protected_div};
+
+
+pub fn eval_expr(expr: &Expr, x: &[f64]) -> f64 {
+// simple stack-based evaluator (scalar); SIMD/vectorized path can be added
+let mut cache: Vec<f64> = vec![0.0; expr.nodes.len()];
+for (i, node) in expr.nodes.iter().enumerate() {
+let val = match node {
+Node::Var(k) => x[*k],
+Node::Const(c) => *c,
+Node::Call(op, ch) => {
+match op {
+Op::Add => cache[ch[0]] + cache[ch[1]],
+Op::Sub => cache[ch[0]] - cache[ch[1]],
+Op::Mul => cache[ch[0]] * cache[ch[1]],
+Op::Div => protected_div(cache[ch[0]], cache[ch[1]]),
+_ => apply_unary(*op, cache[ch[0]]),
+}
+}
+};
+cache[i] = val;
+}
+cache[expr.root]
+}
diff --git a/src/fitness.rs b/src/fitness.rs
new file mode 100644
index 0000000..a00cb78
--- /dev/null
+++ b/src/fitness.rs
@@ -0,0 +1,17 @@
+use crate::ast::Expr;
+use crate::eval::eval_expr;
+
+
+pub fn mse(expr: &Expr, x: &[Vec<f64>], y: &[f64]) -> f64 {
+let n = x.len();
+let mut s = 0.0;
+for i in 0..n {
+let yi = eval_expr(expr, &x[i]);
+let d = yi - y[i];
+s += d * d;
+}
+s / n as f64
+}
+
+
+pub fn complexity(expr: &Expr) -> usize { expr.nodes.len() }
diff --git a/src/gp.rs b/src/gp.rs
new file mode 100644
index 0000000..1b770ff
--- /dev/null
+++ b/src/gp.rs
@@ -0,0 +1,73 @@
+use rand::{seq::SliceRandom, Rng};
+use serde::{Deserialize, Serialize};
+
+
+use crate::ast::{Expr, Node, Op};
+use crate::fitness::{complexity, mse};
+
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct GpConfig {
+pub pop_size: usize,
+pub max_depth: usize,
+pub mutation_rate: f64,
+pub crossover_rate: f64,
+pub gens: usize,
+pub num_vars: usize,
+}
+
+
+impl Default for GpConfig {
+fn default() -> Self {
+Self { pop_size: 256, max_depth: 6, mutation_rate: 0.2, crossover_rate: 0.8, gens: 50, num_vars: 1 }
+}
+}
+
+
+#[derive(Debug, Clone)]
+pub struct Individual { pub expr: Expr, pub err: f64, pub complx: usize }
+
+
+pub struct SymbolicRegressor { pub cfg: GpConfig }
+
+
+impl Default for SymbolicRegressor { fn default() -> Self { Self { cfg: GpConfig::default() } } }
+
+
+impl SymbolicRegressor {
+pub fn new(cfg: GpConfig) -> Self { Self { cfg } }
+
+
+pub fn fit(&self, x: &[Vec<f64>], y: &[f64]) -> Expr {
+let mut rng = rand::thread_rng();
+let mut pop: Vec<Individual> = (0..self.cfg.pop_size)
+.map(|_| Individual { expr: rand_expr(self.cfg.num_vars, self.cfg.max_depth, &mut rng), err: f64::INFINITY, complx: 0 })
+.collect();
+eval_pop(&mut pop, x, y);
+for _gen in 0..self.cfg.gens {
+pop.sort_by(|a,b| a.err.partial_cmp(&b.err).unwrap());
+let elite = pop[0].clone();
+let mut next = vec![elite];
+while next.len() < pop.len() {
+if rng.gen::<f64>() < self.cfg.crossover_rate {
+let (a,b) = tournament2(&pop, &mut rng);
+next.push(crossover(&a.expr, &b.expr, &mut rng));
+} else if rng.gen::<f64>() < self.cfg.mutation_rate {
+let a = &pop[rng.gen_range(0..pop.len())];
+next.push(mutate(&a.expr, self.cfg.num_vars, self.cfg.max_depth, &mut rng));
+} else {
+next.push(pop[rng.gen_range(0..pop.len())].clone());
+}
+}
+pop = next;
+eval_pop(&mut pop, x, y);
+}
+pop.sort_by(|a,b| a.err.partial_cmp(&b.err).unwrap());
+pop[0].expr.clone()
+}
+}
+
+
+fn eval_pop(pop: &mut [Individual], x: &[Vec<f64>], y: &[f64]) {
+pop.iter_mut().for_each(|ind| {
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..26bee8a
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,10 @@
+pub mod ast;
+pub mod eval;
+pub mod ops;
+pub mod fitness;
+pub mod gp;
+pub mod simplify;
+pub mod utils;
+
+
+pub use crate::gp::{GpConfig, SymbolicRegressor};
diff --git a/src/ops.rs b/src/ops.rs
new file mode 100644
index 0000000..4aa43d6
--- /dev/null
+++ b/src/ops.rs
@@ -0,0 +1,17 @@
+use crate::ast::Op;
+
+
+pub fn protected_div(a: f64, b: f64) -> f64 {
+if b.abs() < 1e-12 { a } else { a / b }
+}
+
+
+pub fn apply_unary(op: Op, x: f64) -> f64 {
+match op {
+Op::Sin => x.sin(),
+Op::Cos => x.cos(),
+Op::Exp => x.exp(),
+Op::Log => if x.abs() < 1e-12 { 0.0 } else { x.abs().ln() },
+_ => unreachable!("not unary"),
+}
+}
diff --git a/src/simplify/mod.rs b/src/simplify/mod.rs
new file mode 100644
index 0000000..a4b5b6c
--- /dev/null
+++ b/src/simplify/mod.rs
@@ -0,0 +1 @@
+pub mod rules;
diff --git a/src/simplify/rules.rs b/src/simplify/rules.rs
new file mode 100644
index 0000000..dd01823
--- /dev/null
+++ b/src/simplify/rules.rs
@@ -0,0 +1 @@
+// placeholder for local simplification rules; egg-based rules can live in crates/egg-rewrites