1 files changed, 73 insertions, 0 deletions
diff --git a/lab04/vector_math.h b/lab04/vector_math.h
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+++ b/lab04/vector_math.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#ifndef VECTOR_MATH_H
+#define VECTOR_MATH_H
+
+#include <math.h>
+
+#include "vec.h"
+
+/* Real vectors use a double-typed struct vec. Destinations may alias inputs. */
+static inline bool vector_add(struct vec *dst,
+                              const struct vec *lhs,
+                              const struct vec *rhs)
+{
+    if (lhs->size != rhs->size) return false;
+
+    struct vec temporary;
+    vec_init(&temporary, double);
+    if (!vec_resize(&temporary, lhs->size)) return false;
+    double *result = temporary.data;
+    const double *left = lhs->data;
+    const double *right = rhs->data;
+    for (size_t i = 0; i < lhs->size; ++i) {
+        result[i] = left[i] + right[i];
+    }
+    vec_swap(dst, &temporary);
+    vec_destroy(&temporary);
+    return true;
+}
+
+static inline bool vector_sub(struct vec *dst,
+                              const struct vec *lhs,
+                              const struct vec *rhs)
+{
+    if (lhs->size != rhs->size) return false;
+
+    struct vec temporary;
+    vec_init(&temporary, double);
+    if (!vec_resize(&temporary, lhs->size)) return false;
+    double *result = temporary.data;
+    const double *left = lhs->data;
+    const double *right = rhs->data;
+    for (size_t i = 0; i < lhs->size; ++i) {
+        result[i] = left[i] - right[i];
+    }
+    vec_swap(dst, &temporary);
+    vec_destroy(&temporary);
+    return true;
+}
+
+static inline bool vector_cosine(const struct vec *lhs,
+                                 const struct vec *rhs,
+                                 double *result)
+{
+    if (lhs->size != rhs->size) return false;
+
+    double dot = 0.0;
+    double norm_lhs = 0.0;
+    double norm_rhs = 0.0;
+    for (size_t i = 0; i < lhs->size; ++i) {
+        double left = ((const double *)lhs->data)[i];
+        double right = ((const double *)rhs->data)[i];
+        dot += left * right;
+        norm_lhs += left * left;
+        norm_rhs += right * right;
+    }
+    if (norm_lhs == 0.0 || norm_rhs == 0.0) return false;
+    *result = dot / (sqrt(norm_lhs) * sqrt(norm_rhs));
+    return true;
+}
+
+#endif /* VECTOR_MATH_H */