Add pysim - Python port of C++SIM

README.md

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+# C++SIM
+
+## Python Port Now Available
+
+**PySim** brings C++SIM's battle-tested discrete event simulation to Python 3.12+, preserving the API that has served researchers and engineers since 1990 while leveraging modern Python tooling.
+
+### What You Get
+
+- **SIMULA-style process-based simulation** - The same programming model, now with Python generators instead of OS threads
+- **Validated accuracy** - 77 tests verify numerical equivalence with C++SIM output
+- **Complete feature set**:
+  - Process scheduling (activate, hold, passivate, interrupt)
+  - Entity synchronization (Semaphore, TriggerQueue)
+  - Random streams (Uniform, Exponential, Normal, Erlang, HyperExponential, Triangular)
+  - Statistics collection (Mean, Variance, Histogram, Quantile)
+  - SimSet linked lists
+- **Type hints throughout** for IDE support and static analysis
+- **SimPy integration** - Built on a proven simulation engine
+
+### Quick Start
+
+```bash
+cd pysim && pip install -e .
+```
+
+```python
+from pysim import Process, Scheduler
+import simpy
+
+class Job(Process):
+    def body(self):
+        print(f"Job started at {self.current_time()}")
+        yield from self.hold(10.0)
+        print(f"Job finished at {self.current_time()}")
+
+env = simpy.Environment()
+Scheduler.scheduler(env)
+Job(env).activate()
+env.run()
+```
+
+See [pysim/README.md](pysim/README.md) for full documentation, API reference, and migration guide.
+
+---
+
+## C++SIM (Original)
+
 C++SIM is an object-oriented simulation package which has been under development and available since 1990. It provides discrete event process-based simulation similar to SIMULA's simulation class and libraries. A complete list of the facilities provided follows:
 
 - the core of the system gives SIMULA-like simulation routines, random number generators, queueing algorithms, and thread package interfaces.

pysim/.gitignore

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+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# Virtual environments
+.venv/
+venv/
+ENV/
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+.tox/
+.nox/
+
+# mypy
+.mypy_cache/
+
+# uv
+uv.lock

pysim/CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0] - 2026-01-19
+
+### Added
+- Initial Python port of C++SIM discrete event simulation library
+- Core classes: Process, Scheduler
+- Entity/Event classes: Entity, Semaphore, TriggerQueue
+- Random streams: UniformStream, ExponentialStream, NormalStream, ErlangStream, HyperExponentialStream, TriangularStream, Draw
+- Statistics: Mean, Variance, Histogram, PrecisionHistogram, SimpleHistogram, Quantile, TimeVariance, Pareto
+- SimSet linked lists: Head, Link, Linkage (SIMULA SIMSET equivalents)
+- 77 validation tests against C++ expected_output files
+- Example scripts: producer_consumer.py, machine_shop.py, stats_demo.py
+
+### Changed
+- Uses SimPy as underlying simulation engine instead of pthreads
+- Generator-based coroutines instead of OS threads
+- Python 3.12+ required
+
+### Notes
+- PRNG produces identical sequences to C++SIM with same seeds
+- API mirrors C++SIM where possible, adapted for Python idioms
+- All `hold()`, `wait()`, and semaphore operations require `yield from`