add examples; do not hard-shutdown when screen is closed - destructors did not run!

examples/buf_io_frequency_analysis.csn

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+(
+    ; Perform frequency analysis of the input stream. Pipe a file to this program.
+    (def MINCH 33) ; lowest counted char
+    (def MAXCH 126) ; highest counted char
+    
+    (sym tab r7)
+    (mkbf tab 128)
+    
+    (sym ch r6)
+    (sym sum r1)
+    (sym max r2)
+    (:rch)
+        (ld ch @cin (eof? (j :rch_end)))
+        (rcmp ch MINCH MAXCH (ne? (j :rch)))
+        (bfrd r0 @tab ch)
+        (inc r0) (inc sum)
+        (cmp r0 max (>? (ld max r0)))
+        (bfwr @tab ch r0)
+        (j :rch)
+    (:rch_end)
+
+    (sym fac r3)    
+    (div fac 100_000 max)
+
+    (ld ch MINCH)
+    (:print)
+        (bfrd r0 @tab ch)        
+        (cmp r0 max
+            (eq?
+                (ld @cout 27) (ld @cout '[') (ld @cout '3') (ld @cout '2') (ld @cout 'm'))
+        )
+        (tst r0 (z? (j :print_next)))        
+        (mul r0 fac)
+        (div r0 1000)        
+        (ld @cout ch)
+        (ld @cout ' ')
+        (call bar r0)
+    (:print_next)
+        (ld @cout 27) (ld @cout '[') (ld @cout 'm')
+        (inc ch)
+        (cmp ch MAXCH (le? (j :print)))                
+    (proc bar/1
+        (ld r0 arg0)
+        (:bar)
+            (ld @cout '#')
+            (dec r0 (nz? (j :bar)))   
+        (ld @cout '\n') 
+        (ret)
+    )
+)

examples/buf_io_hello.csn

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+(
+    ; This program asks for a name and prints a greeting
+    
+    (sym name r7)
+    
+    (mkbf r0 "Your name: ") 
+    (call prompt r0) (del @r0)
+    (ld name res0)
+    
+    (ld @cout '\n')
+    
+    (mkbf r1 "Hello, ")
+    (call print r1) (del @r1)
+    (call print name) (del @name)
+    (ld @cout '!')
+    (ld @cout '\n')
+    (halt)
+
+    (proc print buf
+        (bfsz r1 @buf)
+        (:next)
+            (cmp r0 r1 (eq? (ret)))
+            (bfrd @cout @buf r0)
+            (inc r0)
+            (j :next)
+    )
+    
+    (proc prompt msg
+        (call print msg) 
+        (sym dest r7)
+        (mkbf dest)   
+        (:char)
+            (ld r0 @cin (eof? (ret dest)))
+            (cmp r0 '\n' (eq? (ret dest)))
+            (ld @cout r0)
+            (bfpush @dest r0)
+            (j :char)
+    )
+)

examples/itoa.csn

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+(
+    ; This is an example implementation of itoa using a buffer of characters
+    (ld r0 -123456789)
+    
+    (mkbf r1)
+    (call itoa r1 r0)
+    
+    ; print it
+    (:pn) (bfrpop @cout @r1 (em? (ld @cout '\n') (halt))) (j :pn)
+    (halt)
+    
+    (proc itoa buf num    
+        (ld r1 num)
+        (tst r1 (<0? (mul r1 -1)))
+        (:next)
+            (mod r0 r1 10)
+            (add r0 '0')
+            (bfrpush @buf r0)
+            (div r1 10 (z? 
+                (tst num (<0? (bfrpush @buf '-')))
+                (ret)))
+            (j :next)
+    )
+)