IFS in C (#714)

* Add IFS.c

* Updating IFS.md

Author: Gathros

contents/IFS/IFS.md

@@ -132,6 +132,8 @@ Here, instead of tracking children of children, we track a single individual tha
 [import:39-52, lang:"cpp"](code/c++/IFS.cpp)
 {% sample lang="py" %}
 [import:5-12, lang:"python"](code/python/IFS.py)
+{% sample lang="c" %}
+[import:18-29, lang:"c"](code/c/IFS.c)
 {% endmethod %}
 
 If we set the initial points to the on the equilateral triangle we saw before, we can see the Sierpinski triangle again after a few thousand iterations, as shown below:
@@ -199,6 +201,8 @@ In addition, we have written the chaos game code to take in a set of points so t
 [import, lang:"cpp"](code/c++/IFS.cpp)
 {% sample lang="py" %}
 [import, lang:"python"](code/python/IFS.py)
+{% sample lang="c" %}
+[import, lang:"c"](code/c/IFS.c)
 {% endmethod %}
 
 ### Bibliography

contents/IFS/code/c/IFS.c

@@ -0,0 +1,49 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+struct point {
+    double x, y;
+};
+
+double drand() {
+    return ((double) rand() / (RAND_MAX));
+}
+
+struct point random_element(struct point *array, size_t n) {
+    return array[rand() % (int)n];
+}
+
+void chaos_game(struct point *in, size_t in_n, struct point *out,
+                size_t out_n) {
+
+    struct point cur_point = {drand(), drand()};
+
+    for (int i = 0; i < out_n; ++i) {
+        out[i] = cur_point;
+        struct point tmp = random_element(in, in_n);
+        cur_point.x = 0.5 * (cur_point.x + tmp.x);
+        cur_point.y = 0.5 * (cur_point.y + tmp.y);
+    }
+}
+
+int main() {
+    struct point shape_points [3] = {{0.0,0.0}, {0.5,sqrt(0.75)}, {1.0,0.0}};
+    struct point out_points[1000];
+
+    srand(time(NULL));
+
+    chaos_game(shape_points, 3, out_points, 1000);
+
+    FILE *fp = fopen("out.dat", "w+");
+
+    for (int i = 0; i < 1000; ++i) {
+        fprintf(fp, "%f\t%f\n", out_points[i].x, out_points[i].y);
+    }
+
+    fclose(fp);
+
+    return 0;
+}
+