life is now better

- Do not generate s.never to skip Else branch
- Add Display impl to SourcePosition
- Correct SourcePositions pointing to the end of a parsed expr instead of the beginning
- Remove 'true', 'always', 'false' and 'never' from README.md

README.md

@@ -98,8 +98,7 @@ These keywords (among others) are used in conditional branches to specify flag t
 - `nem`, `nempty` … Not empty
 - `eof` … EOF
 - `neof` … Not EOF
-- `true`, `always`, `else` … Always true
-- `false`, `never` … Always false
+- `else` … Always true, may be used in the last branch
 
 # Syntax
 

crsn/crsn-sexp/src/error.rs

@@ -19,6 +19,12 @@ pub struct SourcePosition {
     pub index: u32,
 }
 
+impl fmt::Display for SourcePosition {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        write!(f, "{}:{}", self.line, self.column)
+    }
+}
+
 /// Since errors are the uncommon case, they're boxed. This keeps the size of
 /// structs down, which helps performance in the common case.
 ///

crsn/crsn-sexp/src/lib.rs

@@ -331,10 +331,11 @@ fn parse_sexp(s: &str, pos: &mut usize) -> ERes<Sexp> {
     //trace!("parse_sexp {}", pos);
     zspace(s, pos)?;
     let (c, _) = peek(s, *pos)?;
+    let pos0 = *pos;
     let r = if c == '(' {
-        Ok(Sexp::List(parse_list(s, pos)?, spos(s, *pos)))
+        Ok(Sexp::List(parse_list(s, pos)?, spos(s, pos0)))
     } else {
-        Ok(Sexp::Atom(parse_atom(s, pos)?, spos(s, *pos)))
+        Ok(Sexp::Atom(parse_atom(s, pos)?, spos(s, pos0)))
     };
     zspace(s, pos)?;
     r

crsn/src/asm/instr/flatten.rs

@@ -50,7 +50,7 @@ impl Flatten for InstrWithBranches {
                 }
 
                 if cnt != branch_count - 1 && cond == Cond::True {
-                    warn!("\"Else\" conditional used in non-final branch at {}:{}", branch.pos().line, branch.pos().column);
+                    warn!("\"Else\" conditional used in non-final branch at {}", branch.pos());
                 }
 
                 let next_lbl = if cnt == branch_count - 1 {
@@ -68,11 +68,13 @@ impl Flatten for InstrWithBranches {
                     // optimization for single-branch conditionals with a single instruction
                     ops.push(Op { cond: Some(cond), pos: pos.clone(), kind: flattened.remove(0).kind });
                 } else {
+                    if cond != Cond::True { // evoid emiting `op.never`
                         ops.push(Op {
                             kind: OpKind::BuiltIn(BuiltinOp::Jump(next_lbl.clone())),
                             pos: pos.clone(),
                             cond: Some(!cond),
                         });
+                    }
                     ops.extend(flattened);
                 }
 

crsn/src/asm/instr/op.rs

@@ -50,7 +50,10 @@ impl OpTrait for Op {
             OpKind::Ext(op) => op.to_sexp()
         };
 
+        // TODO rewrite to be more readable?
         if let Some(cond) = self.cond {
+            // "true" is used for "else" branches, it has no effect - just omit it
+            if cond != Cond::True {
                 if let Sexp::List(items, _) = &mut se {
                     if let Some(Sexp::Atom(Atom::S(s), _)) = &mut items.get_mut(0) {
                         s.push('.');
@@ -58,6 +61,7 @@ impl OpTrait for Op {
                     }
                 }
             }
+        }
 
         se
     }

examples/life.csn

@@ -0,0 +1,242 @@
+(
+    ; simple GOL with screen and a buffer + DRAWING!!!
+    
+    ; Middle-click to payse or resume 
+    ; (hold the button until paused - there is a sleep between generations and checking buttons)
+    ;
+    ; When paused, draw with left (white) and right (black) mouse buttons
+    ;
+    ; Resume by clicking middle again.
+    
+    (def GENERATION_MS 200)
+
+    ; Real pixel size
+    (sc-init 400 400)
+    ; Upscaling factor (bug pixels)
+    (sc-opt SCREEN_UPSCALE 10)
+    
+    ; Number of big pixels
+    (def W 40)
+    (def H 40)
+    
+    ; !!! If you change size, also update the following constants.
+    ;     Compile-time math is not implemented yet.
+    
+    (def XMAX 39) ; W-1
+    (def YMAX 39) ; H-1
+    (def NCELLS 1600) ; W*H
+        
+    ; --- end of config ---
+    (sc-opt SCREEN_AUTO_BLIT 0)
+    
+    (sc-erase 0) ; all black
+    (sym ng g15)
+    (mkbf ng NCELLS)
+    
+    ; one glider
+    (bfwr @ng 1 1)
+    (bfwr @ng 42 1)
+    (bfwr @ng 80 1)
+    (bfwr @ng 81 1)
+    (bfwr @ng 82 1)
+    
+    ; another glider
+    (bfwr @ng 16 1)
+    (bfwr @ng 55 1)
+    (bfwr @ng 95 1)
+    (bfwr @ng 96 1)
+    (bfwr @ng 97 1)
+    
+    
+    (def LBTN 0)
+    (def RBTN 1)
+    (def MBTN 2)
+                
+    (:loop)
+        (sc-poll)
+        
+        ; Drawing
+        (sc-mbtn _ MBTN
+            (nz?
+                (:release)
+                    (sc-poll)
+                    (mslp 10)
+                    (sc-mbtn _ MBTN (nz? (j :release)))
+                    
+                (:mousing)
+                    (sc-poll)
+                    (mslp 10)
+                    
+                    (ld r3 -1)
+                    
+                    (sc-mbtn _ LBTN)
+                    (ld.nz r3 1)
+                    (sc-mbtn _ RBTN)
+                    (ld.nz r3 0)
+                    
+                    (tst r3 (nneg?
+                        (sc-mouse r0 r1)
+                        
+                        (tst r3)
+                        (sc-wr.nz r0 r1 #ffffff)
+                        (sc-wr.z r0 r1 #000000)
+                        
+                        (sc-blit)
+                        (mul r1 W)
+                        (add r0 r1)
+                        (ld8 r3:8 r3)
+                        (bfwr @ng r0 r3)
+                    ))                    
+                    
+                    (sc-mbtn _ MBTN 
+                        (z? (j :mousing)))
+                        
+                (:release2)
+                    (sc-poll)
+                    (mslp 10)
+                    (sc-mbtn _ MBTN (nz? (j :release2)))
+            )
+        )       
+        
+        (call Display)
+        (sc-blit)
+        (mslp GENERATION_MS)
+        (j :loop)
+    
+    (proc CountNeighbors x y
+        (sym xx r4)
+        (sym yy r5)
+        (sym i r6)
+        (sym count r7)     
+        
+        ; yeah this sucks. it's correct, though
+        
+        (:a)
+            (add yy y -1 (neg? (j :d)))        
+            (add xx x -1 (neg? (j :b)))
+            (mul i yy W)
+            (add i xx)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+            
+        (:b)
+            (mul i yy W)
+            (add i x)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+        
+        (:c)
+            (add xx x 1)
+            (cmp xx W (ge? (j :d)))
+            (mul i yy W)
+            (add i xx)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+        
+        (:d)     
+            (add xx x -1 (neg? (j :f)))
+            (mul i y W)
+            (add i xx)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+            
+        ; there is no E
+            
+        (:f)
+            (add xx x 1)
+            (cmp xx W (ge? (j :g)))
+            (mul i y W)
+            (add i xx)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+                 
+        (:g)
+            (add yy y 1)        
+            (cmp yy H (ge? (j :end)))
+            (add xx x -1 (neg? (j :h)))
+            (mul i yy W)
+            (add i xx)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+            
+        (:h)
+            (add yy y 1)        
+            (cmp yy H (ge? (j :end)))
+            (mul i yy W)
+            (add i x)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+        
+        (:i)
+            (add yy y 1)        
+            (cmp yy H (ge? (j :end)))
+            (add xx x 1)
+            (cmp xx W (ge? (j :end)))
+            (mul i yy W)
+            (add i xx)
+            (bfrd r0 @ng i)
+            (and r0 0xFF (nz? (inc count)))
+        
+        (:end)
+        (ret count)
+    )
+    
+    (proc Display
+        ; display and calc next gen
+        (sym x r4)
+        (sym y r5)
+        (sym i r6)        
+        (:next)
+            ; The lower byte contains 0 or 1
+            ; the second byte will be filled with the next gen
+            
+            (bfrd r0 @ng i)
+            
+            ; Show this gen
+            (and r0 0xFF 
+                (nz? (sc-wr x y 0xffffff))
+                (z? (sc-wr x y 0x000000)))
+            
+            (call CountNeighbors x y)
+            
+            ; stay: 2,3
+            ; die:  >3
+            ; born: 3
+            
+            (cmp res0 2 
+                (eq? (ld8 r0:8 r0)) ; stasis
+                (ne?
+                    (tst r0 
+                        (z? 
+                            (cmp res0 3 (eq? (ld8 r0:8 1))) ; birth                
+                        ) 
+                        (nz? 
+                            (cmp res0 3 (eq? (ld8 r0:8 1))) ; stay alive                
+                        )
+                    )
+                )
+            )
+            
+            (bfwr @ng i r0)
+            
+            (inc i)
+            (inc x)
+            (cmp x W
+                (ne? (j :next)))
+            (ld x 0)
+            (inc y)
+            (cmp y H 
+                (eq? (j :next2)))
+            (j :next)
+                   
+        ; Shift all by 8 to the right (generation shift)
+        (:next2)
+            (dec i)
+            (bfrd r0 @ng i)
+            (lsr r0 8)
+            (bfwr @ng i r0)
+            (tst i)
+            (j.nz :next2)
+            (ret)
+    )
+)

examples/test_cond.csn

@@ -1,4 +1,23 @@
 (
+  ; test else
+
+  (cmp 0 5
+    (eq? (fault))
+    (else? (ld r0 15))
+    (lt? (fault)) ; This should produce a warning
+  )
+  (cmp 15 r0
+    (ne? (fault "else did not run")))
+
+  (ld r0 0)
+
+  (cmp 0 5
+    (lt? (nop))
+    (else? (fault "fallthrough to else"))
+  )
+
+  ;
+
   (ld r8 0)
 
   (ld r0 1