2 files changed, 138 insertions(+), 0 deletions(-)

A list/Makefile
A list/list.c

@@ 0,0 1,14 @@
+.POSIX:
+CC 		= cc
+CFLAGS 	= -std=c99 -Wpedantic -Wall -Wextra -O3
+LDFLAGS = 
+
+all: list
+
+list: list.o
+	$(CC) $(CFLAGS) -o main list.o $(LDFLAGS)
+
+list.o: list.c
+
+clean:
+	rm -f list list.o

@@ 0,0 1,124 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define NUM_ELEMS 15
+
+/* Data constructor names */
+enum list_const {EMPTY, CONS};
+
+/* Actual sum data type */
+struct list {
+        enum list_const type;
+        struct data {
+                int num;
+                struct list *next;
+        } data;
+};
+
+/* Empty list constructor */
+struct list *
+make_empty(struct list *lst)
+{
+        lst->type = EMPTY;
+        lst->data = (struct data) {0};
+
+        return lst;
+}
+
+/* Cons constructor */
+struct list *
+cons(int a, struct list *lst)
+{
+        if (lst) {
+                struct list *new = malloc(sizeof(struct list));
+
+                if (new) {
+                        new->type = CONS;
+                        new->data.num = a;
+                        new->data.next = lst;
+                        lst = new;
+                }
+        }
+
+        return lst;
+}
+
+int
+length(struct list *lst)
+{
+        if (lst) {
+                switch (lst->type) {
+                case EMPTY:
+                        return 0;
+                case CONS:
+                        /* Could use tail recursion */
+                        return 1 + length(lst->data.next);
+                default:
+                        fprintf(stderr, "Non-exhaustive patterns in function "
+                            "%s\n", __func__);
+                }
+        }
+
+        return -1;
+}
+
+struct list *
+map(int (*fun)(int a), struct list *lst)
+{
+        if (lst) {
+                struct list *tmp = lst;
+                while (tmp) {
+                        tmp->data.num = fun(tmp->data.num);
+                        tmp = tmp->data.next;
+                }
+        }
+
+        return lst;
+}
+
+void
+print_list(struct list *lst)
+{
+        switch (lst->type) {
+        case EMPTY:
+                puts("[]");
+                break;
+        case CONS:
+                printf("%d,", lst->data.num);
+                print_list(lst->data.next);
+        }
+}
+
+int
+sum(int a)
+{
+        return a+1;
+}
+
+int
+main(void)
+{
+        struct list *lst = malloc(sizeof(struct list));
+        if (!lst) return EXIT_FAILURE;
+
+        make_empty(lst);
+        print_list(lst);
+
+        for (int i = 1; i <= NUM_ELEMS; i++) {
+                lst = cons(i, lst);
+        }
+        
+        print_list(lst);
+        printf("Length %d\n", length(lst));
+
+        map(&sum, lst);
+        print_list(lst);
+
+        struct list *curr = 0;
+        while ((curr = lst)) {
+                lst = lst->data.next;
+                free(curr);
+        }
+
+        return EXIT_SUCCESS;
+}