From 997ceb15e2b088f7aa8710970d02d658d1844d3f Mon Sep 17 00:00:00 2001
From: Nao Pross <naopross@thearcway.org>
Date: Sun, 9 Dec 2018 19:21:06 +0100
Subject: Add C 3d vector library example

---
 vector/makefile  |  18 ++++++++++
 vector/vectors.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 vector/makefile
 create mode 100644 vector/vectors.c

diff --git a/vector/makefile b/vector/makefile
new file mode 100644
index 0000000..6ce8fd9
--- /dev/null
+++ b/vector/makefile
@@ -0,0 +1,18 @@
+CARGS   := -Wall -Werror -I.
+CPPARGS := -Wall -Werror -I.
+
+all: cpp-vector.pdf c_build/vectors
+
+%.pdf: %.md
+	pandoc \
+		--latex-engine=xelatex \
+		--filter pandoc-include-code \
+		$< -o $@
+
+c_build/%: %.c
+	mkdir -p c_build
+	gcc $(CARGS) $< -o $@
+
+cpp_build/%: %.cpp
+	mkdir -p cpp_build
+	g++ $(CPPARGS) $< -o $@
diff --git a/vector/vectors.c b/vector/vectors.c
new file mode 100644
index 0000000..c8a5906
--- /dev/null
+++ b/vector/vectors.c
@@ -0,0 +1,107 @@
+#include <stddef.h>
+#include <stdio.h>
+
+struct vec3 {
+    double x;
+    double y;
+    double z;
+};
+
+struct vec3 vec3_add(struct vec3 * const v, struct vec3 * const u)
+{
+    struct vec3 result = {0, 0, 0};
+
+    if (v == NULL || u == NULL)
+        return result;
+
+    result.x = v->x + u->x;
+    result.y = v->y + u->y;
+    result.z = v->z + u->z;
+
+    return result;
+}
+
+struct vec3 vec3_mul(struct vec3 * const v, const double scalar)
+{
+    struct vec3 result = {0, 0, 0};
+
+    if (v == NULL)
+        return result;
+
+    result.x = scalar * v->x;
+    result.y = scalar * v->y;
+    result.z = scalar * v->z;
+
+    return result;
+}
+
+struct vec3 vec3_sub(struct vec3 * const v, struct vec3 * const u)
+{
+    struct vec3 result = {0, 0, 0};
+    
+    result = vec3_mul(u, -1.0);
+    result = vec3_add(v, &result);
+
+    return result;
+}
+
+double vec3_dot(struct vec3 * const v, struct vec3 * const u)
+{
+    if (v == NULL || u == NULL)
+        return 0;
+
+    return (v->x * u->x) + (v->y * u->y) + (v->z * u->y);
+}
+
+struct vec3 vec3_cross(struct vec3 * const v, struct vec3 * const u)
+{
+    struct vec3 result = {0, 0, 0};
+
+    result.x = (v->y * u->z) - (v->z * u->y);
+    result.y = (v->z * u->x) - (v->x * u->z);
+    result.z = (v->x * u->y) - (v->y * u->x);
+
+    return result;
+}
+
+void vec3_print(struct vec3 * const v)
+{
+    if (v == NULL)
+        return;
+
+    printf("<%.2f,%.2f,%.2f>\n", v->x, v->y, v->y);
+}
+
+
+int main(int argc, char *argv[])
+{
+    struct vec3 a = {1, 2, 3};
+    struct vec3 b = {4, 5, 6};
+    struct vec3 res;
+
+    printf("a = ");
+    vec3_print(&a);
+    printf("b = ");
+    vec3_print(&b);
+
+    printf("sum a + b     : ");
+    res = vec3_add(&a, &b);
+    vec3_print(&res);
+
+    printf("sub a - b     : ");
+    res = vec3_sub(&a, &b);
+    vec3_print(&res);
+
+    printf("product 3*a   : ");
+    res = vec3_mul(&a, 3);
+    vec3_print(&res);
+
+    printf("dot product   : ");
+    printf("%.2f\n", vec3_dot(&a, &b));
+
+    printf("cross product : ");
+    res = vec3_cross(&a, &b);
+    vec3_print(&res);
+
+    return 0;
+}
-- 
cgit v1.2.1