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

crsn_screen/src/exec.rs

@@ -97,9 +97,9 @@ impl OpTrait for ScreenOp {
                 let backend: &mut Backend = state.ext_mut();
 
                 if force != 0 {
-                    blit(backend)
+                    blit(backend)?;
                 } else {
-                    blit_maybe(backend)
+                    blit_maybe(backend)?;
                 }
             }
 
@@ -143,7 +143,7 @@ impl OpTrait for ScreenOp {
                             backend.buffer[index as usize] = color as u32;
 
                             if backend.opts.auto_blit {
-                                blit_maybe(backend);
+                                blit_maybe(backend)?;
                             }
                         }
                     }
@@ -274,29 +274,31 @@ fn init(state: &mut RunState, width: Value, height: Value) -> Result<(), Fault>
 
     backend.window = Some(window);
 
-    blit_maybe(backend);
+    blit_maybe(backend)?;
 
     Ok(())
 }
 
-fn blit_maybe(backend: &mut Backend) {
+fn blit_maybe(backend: &mut Backend) -> Result<(), Fault> {
     if backend.last_render.elapsed() >= backend.opts.frame_rate {
-        blit(backend);
+        blit(backend)
+    } else {
+        Ok(())
     }
 }
 
-fn blit(backend: &mut Backend) {
+fn blit(backend: &mut Backend) -> Result<(), Fault> {
     let w = backend.window.as_mut().unwrap();
 
     if !w.is_open() {
-        // TODO...
+        return Err(Fault::Halt);
-        std::process::exit(0);
     }
 
     w.update_with_buffer(&backend.buffer, backend.width, backend.height)
         .expect("Update screen"); // TODO fault
 
     backend.last_render = Instant::now();
+    Ok(())
 }
 
 fn num2key(num: Value) -> Option<Key> {

examples/buf_io_frequency_analysis.csn

@@ -0,0 +1,50 @@
+(
+    ; 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

@@ -0,0 +1,39 @@
+(
+    ; 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

@@ -0,0 +1,24 @@
+(
+    ; 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)
+    )
+)