first commit!

typeconversions.c

@@ -0,0 +1,21 @@
+#include <ctype.h>
+#include <stdio.h>
+
+int atoi(char s[]);
+
+int main() {
+  printf("%d\n", atoi("234"));
+}
+
+int atoi(char string[]) {
+  int n = 0;
+  /*
+  * v1
+  for (int i = 0; string[i] >= '0' && string[i] <= '9'; ++i)
+    n = 10 * n + (string[i] - '0');
+  */
+  for (int i = 0; isdigit(string[i]); ++i)
+    n = 10 * n + (string[i] - '0');
+
+  return n;
+}