Fix order of operands in word-sized cmp.

doc/SixtyPical.md

@@ -398,6 +398,9 @@ and initializing them afterwards.
 
 Subtracts the contents of src from dest (without considering carry) but
 does not store the result anywhere, only sets the resulting flags.
+This means that `z` is set if src and dest are equal,
+and `c` is set if dest is greater than or equal to src
+(`c` is unset if dest is less than src.)
 
 *   It is illegal if src OR dest is uninitialized.
 
@@ -407,7 +410,7 @@ and initializing them afterwards.
 In addition, if dest is of `word` type, then src must also be of `word`
 type, and in this case this instruction trashes the `a` register.
 
-Note that, like `cmp` is not suitable for making a
+Note that `cmp` is not suitable for making a
 signed comparison; this article, which mentions
 techniques that a SixtyPical compiler could use to
 implement `cmp`, also explains why that is:

eg/rudiments/cmp-byte.60p

@@ -52,7 +52,7 @@ define main routine
 
     ld a, 20
 
-    cmp a, b      // 20 >= 21
+    cmp a, b      // 20 >= 20
     if c {
         ld a, 71  // G
         call chrout
@@ -63,7 +63,7 @@ define main routine
 
     ld a, 19
 
-    cmp a, b      // 19 < 21
+    cmp a, b      // 19 < 20
     if c {
         ld a, 71  // G
         call chrout

src/sixtypical/compiler.py

@@ -394,12 +394,12 @@ class Compiler(object):
         if isinstance(src, LocationRef) and src.type == TYPE_WORD:
             src_label = self.get_label(src.name)
             dest_label = self.get_label(dest.name)
-            self.emitter.emit(LDA(Absolute(src_label)))
-            self.emitter.emit(CMP(Absolute(dest_label)))
+            self.emitter.emit(LDA(Absolute(dest_label)))
+            self.emitter.emit(CMP(Absolute(src_label)))
             end_label = Label('end_label')
             self.emitter.emit(BNE(Relative(end_label)))
-            self.emitter.emit(LDA(Absolute(Offset(src_label, 1))))
-            self.emitter.emit(CMP(Absolute(Offset(dest_label, 1))))
+            self.emitter.emit(LDA(Absolute(Offset(dest_label, 1))))
+            self.emitter.emit(CMP(Absolute(Offset(src_label, 1))))
             self.emitter.resolve_label(end_label)
             return
         cls = {

tests/SixtyPical Compilation.md

@@ -396,11 +396,11 @@ Compiling 16-bit `cmp`.
     | {
     |     cmp za, zb
     | }
-    = $080D   LDA $081C
-    = $0810   CMP $EA61
+    = $080D   LDA $EA61
+    = $0810   CMP $081C
     = $0813   BNE $081B
-    = $0815   LDA $081D
-    = $0818   CMP $EA62
+    = $0815   LDA $EA62
+    = $0818   CMP $081D
     = $081B   RTS
     = $081C   .byte $BB
     = $081D   .byte $0B