add generator example

examples/coroutines2.csn

@@ -0,0 +1,44 @@
+(
+    ; using a coroutine as a generator
+
+    (spawn r15 fibo)
+
+    (ld r0 20)
+    (:next)
+
+    (ld r1 @r15) ; Read a yielded value
+    (call printnum r1)
+    (lds @cout ", ")
+
+    (dec r0)
+    (j.nz :next)
+    (ld @cout '\n')
+    (halt)
+
+    (proc fibo
+        (ld r0 0)
+        (ld r1 1)
+        (:x)
+        (yield r1)
+        (add r2 r0 r1)
+        (ld r0 r1)
+        (ld r1 r2)
+        (j :x)
+    )
+
+    (proc printnum num
+        (mkbf r15)
+        (ld r1 num)
+        (tst r1 (<0? (mul r1 -1)))
+        (:next)
+            (mod r0 r1 10)
+            (add r0 '0')
+            (bfrpush @r15 r0)
+            (div r1 10 (z?
+                (tst num (<0? (bfrpush @r15 '-')))
+                (lds @cout @r15)
+                (del @r15)
+                (ret)))
+            (j :next)
+    )
+)

examples/itoa.csn

@@ -21,4 +21,21 @@
                 (ret)))
             (j :next)
     )
+
+    ; other version that prints it
+    (proc printnum num
+        (mkbf r15)
+        (ld r1 num)
+        (tst r1 (<0? (mul r1 -1)))
+        (:next)
+            (mod r0 r1 10)
+            (add r0 '0')
+            (bfrpush @r15 r0)
+            (div r1 10 (z?
+                (tst num (<0? (bfrpush @r15 '-')))
+                (lds @cout @r15)
+                (del @r15)
+                (ret)))
+            (j :next)
+    )
 )