add new example for designated initializers (ch. 10)

21st_century_c/Makefile

@@ -1,17 +1,20 @@
 CFLAGS = --std=c11 -Wall -O3
 
 
+boxes : boxes.c
+	$(CC) $(CFLAGS) $@.c -o $@
+
 show_tree : process_dir.h process_dir.c show_tree.c
 	$(CC) $(CFLAGS) process_dir.c $@.c -o $@
 
 simple_cplx : cplx.h complex.c simple_cplx.c
 	$(CC) `pkg-config --cflags --libs gsl` $(CFLAGS) complex.c $@.c -o $@
 
-
 .PHONY : all
-all : show_tree simple_cplx
+all : boxes show_tree simple_cplx
 
 .PHONY : clean
 clean :
+	rm -f boxes
 	rm -f show_tree
 	rm -f simple_cplx

21st_century_c/boxes.c

@@ -0,0 +1,69 @@
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+
+typedef struct {
+  char *name;
+  int left, right, up, down;
+} direction_s;
+
+
+void this_row(direction_s d);
+void draw_box(direction_s d);
+
+
+int main() {
+
+  direction_s D = {.name = "left", .left = 1};
+  draw_box(D);
+
+  // name is first, so we can omit label
+  D = (direction_s) {"upper right", .up = 1, .right = 1};
+  draw_box(D);
+
+  // all struct elements set to zero
+  draw_box((direction_s){});
+
+}
+
+
+void this_row(direction_s d) {
+
+  char s[] = ".*.\n";
+
+  if(d.left) {
+    strlcpy(s, "*..\n", sizeof(s));
+  } else if(d.right) {
+    strlcpy(s, "..*\n", sizeof(s));
+  }
+
+  printf("%s", s);
+
+}
+
+
+void draw_box(direction_s d) {
+
+  printf("%s:\n", (d.name ? d.name : "a box"));
+
+
+  if(d.up) {
+    this_row(d);
+  } else {
+    printf("...\n");
+  }
+  if(!d.up && !d.down) {
+    this_row(d);
+  } else {
+    printf("...\n");
+  }
+  if(d.down) {
+    this_row(d);
+  } else {
+    printf("...\n");
+  }
+  printf("\n");
+
+}