M examples/factorial.xyw → examples/factorial.xyw

@@ -1,12 +1,53 @@ 
-; main program
-$5 fact JSRw
-$0 system.state STBw
+.include "devices.xyw"
 
-; a8 --
+; ;ain program: calculate and print factorial of 5
+$5 fact JSRw 
+print8 JSRw
+$0A terminal.output STB
+end JMPw
+
+; Factorial subroutine
+; a8 -- | [xy]
 .label fact
-  $1 EQU fact.end JCNw
-  INC MUL 
-  fact JMPw
-  .label fact.end
-    ; TODO: print
-    RTS+  ; Save argument to both registers
+  POPxy
+  .label fact.loop 
+    PSHy $0 EQU fact.end0 JCNw
+    PSHy $1 EQU fact.end1 JCNw
+    ; Decrement y and multiply
+    DECy PSHx PSHy MULx POPx
+    fact.loop JMPw
+  .label fact.end0
+    ; Edge case: factorial of 0 is 1
+    $1
+    CLRxy
+    RTS
+  .label fact.end1
+    ; Return result
+    PSHx
+    CLRxy
+    RTS
+
+; Printing subroutine
+; a8 -- | [xy]
+.label print8
+  POPx 
+  ; If value is less than 10, print single digit
+  PSHx $A LTH print8.single JCNw
+  ; Divide by 10: stack becomes [remainder, quotient]
+  PSHx $A DIV
+  ; Save remainder to y for later
+  SWP POPy
+  ; Call print8 recursively with quotient (still on stack)
+  print8 JSRw
+  ; Print the saved remainder
+  PSHy $30 ADD terminal.output STB
+  CLRxy
+  RTS
+  .label print8.single
+    ; Print single digit
+    PSHx $30 ADD terminal.output STB 
+    CLRx
+    RTS
+
+.label end

M test.sh → test.sh

@@ -7,6 +7,7 @@ "run_test helloworld.xyw assert_output_equals \$'Hello, World!\\n'"
   "run_test d6.xyw assert_output_in_range 1 6"
   "run_test on-error.xyw assert_output_equals \$'Error: Division by zero.\\nError: Unknown error.\\n'"
   "run_test print-args.xyw test1 test2 -- assert_output_equals \$'print-args.xim, test1, test2\\n'"
+  "run_test factorial.xyw assert_output_equals \$'120\\n'"
 )
 
 ### Helper functions

M xywrun.c → xywrun.c

@@ -226,10 +226,10 @@ // clang-format off
 
 //// Operations that support stack and all registers
 #define OPC_SR2(opc, body) { \
-    case opc: { const int w=0, rx=0, ry=0; xyw_byte b = us_pop(), a = us_pop(); body; (void)(rx); (void)(ry); } break; \
-    case XYW_MODE_X|opc: { const int w=0, rx=1, ry=0; xyw_byte b = *x, a = us_pop(); body; (void)(rx); (void)(ry); } break; \
-    case XYW_MODE_Y|opc: { const int w=0, rx=0, ry=1; xyw_byte b = *y, a = us_pop(); body; (void)(rx); (void)(ry); } break; \
-    case XYW_MODE_X|XYW_MODE_Y|opc: { const int w=0, rx=1, ry=1; xyw_byte a = *x, b = *y; body; (void)(rx); (void)(ry); } break; \
+    case opc: { const int w=0, rx=0, ry=0; xyw_byte b = us_pop(); xyw_byte a = us_pop(); body; (void)(rx); (void)(ry); } break; \
+    case XYW_MODE_X|opc: { const int w=0, rx=1, ry=0; xyw_byte b = *x; xyw_byte a = us_pop(); body; (void)(rx); (void)(ry); } break; \
+    case XYW_MODE_Y|opc: { const int w=0, rx=0, ry=1; xyw_byte b = *y; xyw_byte a = us_pop(); body; (void)(rx); (void)(ry); } break; \
+    case XYW_MODE_X|XYW_MODE_Y|opc: { const int w=0, rx=1, ry=1; xyw_byte a = *x; xyw_byte b = *y; body; (void)(rx); (void)(ry); } break; \
     case XYW_MODE_W|opc: { const int w=1, rx=0, ry=0; xyw_word b = us_popw(); xyw_word a = us_popw(); body; (void)(rx); (void)(ry); } break; \
     case XYW_MODE_X|XYW_MODE_W|opc: { const int w=1, rx=1, ry=0; xyw_word b = *xw; xyw_word a = us_popw(); body; (void)(rx); (void)(ry); } break; \
     case XYW_MODE_Y|XYW_MODE_W|opc: { const int w=1, rx=0, ry=1; xyw_word b = *yw; xyw_word a = us_popw(); body; (void)(rx); (void)(ry); } break; \
@@ -253,7 +253,7 @@ case XYW_MODE_X|XYW_MODE_Y|XYW_MODE_W|opc: { const int w=1, rx=1, ry=1; xyw_word a = *xw; xyw_word b = *yw; body;(void)(w);(void)(a);(void)(b);(void)(rx);(void)(ry); } break; \
 }
 
 // Create address based on direct page or full address
-#define ADDR(ad) w ? ad : (DIRECT_PAGE | ad) 
+#define ADDR(ad) (w ? (ad) : (DIRECT_PAGE | (ad)))
 // Push a value to stack
 #define PUSH(n) do { if (w) { us_pushw(n); } else { us_push(n); } } while(0)
 // Pop value from stack
@@ -354,7 +354,7 @@ }
     while ((xyw_memory[SYSTEM_STATE] & SYSTEM_STATE_RUNNING) && *pc < SYSTEM_MEMORY_START)
     {
         process_events();
-        xyw_dbg("PC: %04X -> %02X (%s) [U:%02X|S:%02X|X:%02X|Y:%02X|XW:%04X|YW:%04X]\n", *pc, xyw_memory[*pc], xyw_instructions[xyw_memory[*pc] & 0x1F], *u, *s, *x, *y, *xw, *yw);
+        xyw_dbg(" -- PC: %04X -> %02X (%s) [U:%02X|S:%02X|X:%02X|Y:%02X|XW:%04X|YW:%04X]\n", *pc, xyw_memory[*pc], xyw_instructions[xyw_memory[*pc] & 0x1F], *u, *s, *x, *y, *xw, *yw);
         switch (xyw_memory[*pc])
         {
             // clang-format off
@@ -394,7 +394,7 @@ /* IOR */ OPC_SR2(0x15, PUSH(a | b));
             /* XOR */ OPC_SR2(0x16, PUSH(a ^ b));
             /* NOT */ OPC_SR1(0x17, , SET(~ARG));
             /* NOT */ OPC_SR1r(0x17, SET(~ARGX); SET(~ARGY); );
-            /* SWP */ OPC_SR2(0x18, if ((rx||ry)) { SET(b); } else { PUSH(a); PUSH(b); } );
+            /* SWP */ OPC_SR2(0x18, if ((rx||ry)) { SET(b); } else { PUSH(b); PUSH(a); } );
             /* DUP */ OPC_SR1(0x19, , SET(READ(USER_STACK_START + (*u) - (w ? 2 : 1))));
             /* DUP */ OPC_SR1r(0x19, SETX(READ(USER_STACK_START + (*u) - (w ? 2 : 1))); SETY(READ(USER_STACK_START + (*u) - (w ? 2 : 1))); );
             /* OVR */ OPC_SR2(0x1A, PUSH(b); PUSH(a); PUSH(b));