Replace CMake with Zig build system

.gitignore

@@ -1,4 +1,7 @@
-\build
 .vscode/
-\googletest
-/Generate_Orders/orders.txt
+googletest/
+/Generate_Orders/orders.txt
+
+# Zig
+.zig-cache/
+zig-out/

CLAUDE.md

@@ -0,0 +1,70 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build Commands
+
+```bash
+# Clone GoogleTest (first time only)
+git clone --depth 1 https://github.com/google/googletest.git
+
+# Build
+zig build
+
+# Run tests
+zig build test
+
+# Run executable
+./zig-out/bin/LimitOrderBook
+```
+
+The project uses Zig's build system with C++20 and -O2 optimization. GoogleTest is integrated as a subdirectory.
+
+## Architecture
+
+This is a high-frequency trading limit order book matching engine implementing FIFO/Price Priority algorithm.
+
+### Core Data Structures (Limit_Order_Book/)
+
+**Three-class hierarchy with hybrid data structure design:**
+
+1. **Book** - Main order book engine
+   - Dual AVL trees for buy/sell sides (regular orders)
+   - Dual AVL trees for stop orders (stop buys/sells)
+   - Hash maps for O(1) lookups: `orderMap`, `limitBuyMap`, `limitSellMap`, `stopMap`
+   - Maintains `highestBuy`/`lowestSell` pointers for O(1) best bid/ask access
+
+2. **Limit** - Price level node
+   - AVL tree node (parent/leftChild/rightChild pointers)
+   - Contains doubly-linked list of orders at this price (headOrder/tailOrder)
+   - Tracks totalVolume and size (order count)
+
+3. **Order** - Individual order
+   - Doubly-linked list node within a Limit (nextOrder/prevOrder)
+   - Back-reference to parentLimit for O(1) limit updates
+
+### Time Complexities
+- Add/Cancel/Modify/Execute: O(1) for existing limits, O(log M) for new price levels
+- GetBestBid/Offer: O(1)
+- AVL rebalancing: O(log M) when triggered
+
+### Supporting Modules
+
+- **OrderPipeline** (Process_Orders/) - Dispatcher pattern for order processing with nanosecond latency measurement
+- **GenerateOrders** (Generate_Orders/) - Test data generation with normal distribution
+
+### Order Types Supported
+- Market orders
+- Limit orders
+- Stop orders
+- Stop-limit orders
+
+### Key Design Decisions
+
+1. **AVL + Doubly-Linked List Hybrid** - AVL for O(log M) price navigation, doubly-linked list at each level for O(1) FIFO ordering
+
+2. **Single-threaded matching** - Intentional design for FIFO/price priority consistency
+
+3. **Manual memory management** - Uses new/delete with proper cleanup in destructors
+
+4. **Separate stop order trees** - Parallel data structures isolate regular and stop order handling

README.md

@@ -46,17 +46,34 @@ Limit_Order_Book/
 │ ├── data_visualisation.py
 │ └── order_processing_times.csv
 ├── test/               *unit tests
-│ ├── CMakeLists.txt
 │ ├── ExampleOrdersTests.cpp
 │ └── LimitOrderBookTests.cpp
 ├── figures/
 ├── googletest/
 ├── main.cpp
 ├── .gitignore
-├── CMakeLists.txt
+├── build.zig
 └── README.md
 ```
 
+## Build Instructions
+
+### Prerequisites
+
+- [Zig](https://ziglang.org/download/) (0.13+)
+- Clone GoogleTest (first time only):
+```bash
+git clone --depth 1 https://github.com/google/googletest.git
+```
+
+### Build and Run
+
+```bash
+zig build              # Build
+zig build test         # Run tests
+./zig-out/bin/LimitOrderBook  # Run executable
+```
+
 ## Architecture
 
 <img src="./figures/architecture.png" alt="Architecture" width="800"/>

build.zig

@@ -0,0 +1,134 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    // Common C++ flags
+    const cpp_flags: []const []const u8 = &.{
+        "-std=c++20",
+        "-O2",
+    };
+
+    // =========================================
+    // Static Library: LimitOrderBook_lib
+    // =========================================
+    const lib_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libcpp = true,
+    });
+
+    lib_module.addCSourceFiles(.{
+        .files = &.{
+            "Limit_Order_Book/Book.cpp",
+            "Limit_Order_Book/Limit.cpp",
+            "Limit_Order_Book/Order.cpp",
+            "Process_Orders/OrderPipeline.cpp",
+            "Generate_Orders/GenerateOrders.cpp",
+        },
+        .flags = cpp_flags,
+    });
+
+    const lib = b.addLibrary(.{
+        .name = "LimitOrderBook_lib",
+        .root_module = lib_module,
+    });
+    b.installArtifact(lib);
+
+    // =========================================
+    // Main Executable: LimitOrderBook
+    // =========================================
+    const exe_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libcpp = true,
+    });
+
+    exe_module.addCSourceFiles(.{
+        .files = &.{"main.cpp"},
+        .flags = cpp_flags,
+    });
+
+    exe_module.linkLibrary(lib);
+
+    const exe = b.addExecutable(.{
+        .name = "LimitOrderBook",
+        .root_module = exe_module,
+    });
+    b.installArtifact(exe);
+
+    // Run command: zig build run
+    const run_cmd = b.addRunArtifact(exe);
+    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    const run_step = b.step("run", "Run the limit order book");
+    run_step.dependOn(&run_cmd.step);
+
+    // =========================================
+    // GoogleTest Library
+    // =========================================
+    const gtest_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libcpp = true,
+    });
+
+    gtest_module.addCSourceFiles(.{
+        .files = &.{
+            "googletest/googletest/src/gtest-all.cc",
+            "googletest/googletest/src/gtest_main.cc",
+        },
+        .flags = cpp_flags,
+    });
+
+    gtest_module.addIncludePath(b.path("googletest/googletest/include"));
+    gtest_module.addIncludePath(b.path("googletest/googletest"));
+
+    const gtest = b.addLibrary(.{
+        .name = "gtest",
+        .root_module = gtest_module,
+    });
+
+    // =========================================
+    // Test Executable: LimitOrderBookTests
+    // =========================================
+    const test_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libcpp = true,
+    });
+
+    test_module.addCSourceFiles(.{
+        .files = &.{
+            "test/LimitOrderBookTests.cpp",
+            "test/ExampleOrdersTests.cpp",
+        },
+        .flags = cpp_flags,
+    });
+
+    test_module.addIncludePath(b.path("googletest/googletest/include"));
+    test_module.linkLibrary(lib);
+    test_module.linkLibrary(gtest);
+
+    const tests = b.addExecutable(.{
+        .name = "LimitOrderBookTests",
+        .root_module = test_module,
+    });
+    b.installArtifact(tests);
+
+    // Run tests: zig build test
+    const run_tests = b.addRunArtifact(tests);
+    run_tests.step.dependOn(b.getInstallStep());
+
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_tests.step);
+
+    // Clean step: zig build clean
+    const clean_step = b.step("clean", "Remove build artifacts");
+    clean_step.dependOn(&b.addRemoveDirTree(b.path(".zig-cache")).step);
+    clean_step.dependOn(&b.addRemoveDirTree(b.path("zig-out")).step);
+}