From 7db0d82731ababdf0b2f4d986dd54da3b4650954 Mon Sep 17 00:00:00 2001
From: y-jan137 <yousefjan24000@gmail.com>
Date: Sat, 14 Mar 2026 14:49:46 +0300
Subject: Add triangular solve

---
 include/linalg_error.hpp     |  6 ++++++
 include/triangular_solve.hpp | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 include/triangular_solve.hpp

(limited to 'include')

diff --git a/include/linalg_error.hpp b/include/linalg_error.hpp
index 8258899..25c48ad 100644
--- a/include/linalg_error.hpp
+++ b/include/linalg_error.hpp
@@ -16,4 +16,10 @@ public:
         : LinAlgError(message) {}
 };
 
+class SingularMatrixError : public LinAlgError {
+public:
+    explicit SingularMatrixError(const std::string& message)
+        : LinAlgError(message) {}
+};
+
 }  // namespace linalg
diff --git a/include/triangular_solve.hpp b/include/triangular_solve.hpp
new file mode 100644
index 0000000..632f225
--- /dev/null
+++ b/include/triangular_solve.hpp
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <cstddef>
+
+#include "matrix.hpp"
+#include "vector.hpp"
+
+namespace linalg {
+
+Vector forward_substitution(
+    const Matrix& lower,
+    const Vector& rhs,
+    double singular_tolerance = 1e-12,
+    bool unit_diagonal = false);
+
+Vector backward_substitution(
+    const Matrix& upper,
+    const Vector& rhs,
+    double singular_tolerance = 1e-12,
+    bool unit_diagonal = false);
+
+}  // namespace linalg
-- 
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