Restructured recursive examples

cksystemsteaching · Jul 25, 2019 · 2c10bf2 · 2c10bf2
1 parent b3de1ed
commit 2c10bf2
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Showing 3 changed files with 17 additions and 16 deletions.
diff --git a/manuscript/code/symbolic/nested-recursion.c b/manuscript/code/symbolic/nested-recursion.c
@@ -9,17 +9,17 @@ Input == #b00110001 (== 49 == '1')
 */
 
 uint64_t factorial_upwards(uint64_t n) {
-  if (n < 10)
-    return n * factorial_upwards(n + 1);
-  else
+  if (n >= 10)
     return n;
+  else
+    return n * factorial_upwards(n + 1);
 }
 
 uint64_t modified_factorial(uint64_t n) {
-  if (n <= 1)
-    return factorial_upwards(1);
-  else
+  if (n > 1)
     return n * modified_factorial(n - 1);
+  else
+    return factorial_upwards(1);
 }
 
 uint64_t main() {

diff --git a/manuscript/code/symbolic/recursive-ackermann.c b/manuscript/code/symbolic/recursive-ackermann.c
@@ -9,12 +9,13 @@ Input == #b00110001 (== 49 == '1')
 */
 
 uint64_t ackermann(uint64_t m, uint64_t n) {
-  if (m == 0)
+  if (m != 0) {
+    if (n != 0)
+      return ackermann(m - 1, ackermann(m, n - 1));
+    else
+      return ackermann(m - 1, 1);
+  } else
     return n + 1;
-  else if (n == 0)
-    return ackermann(m - 1, 1);
-  else
-    return ackermann(m - 1, ackermann(m, n - 1));
 }
 
 uint64_t main() {

diff --git a/manuscript/code/symbolic/recursive-factorial.c b/manuscript/code/symbolic/recursive-factorial.c
@@ -9,10 +9,10 @@ Input == #b00110001 (== 49 == '1')
 */
 
 uint64_t factorial(uint64_t n) {
-  if (n <= 1)
-    return n;
-  else
+  if (n > 1)
     return n * factorial(n - 1);
+  else
+    return n;
 }
 
 uint64_t main() {
@@ -23,11 +23,11 @@ uint64_t main() {
 
   read(1, x, 1);
 
-  *x = *x - 35;
+  *x = *x - 39;
 
   a = factorial(*x);
 
-  if (a == 87178291200)
+  if (a == 3628800)
     return 1;
   else
     return 0;