From 6e0ca3838e7d6c1e7008d6bd83c0b5b365021fdd Mon Sep 17 00:00:00 2001
From: Chris Pressey <cpressey@catseye.tc>
Date: Tue, 20 Oct 2015 14:39:32 +0100
Subject: [PATCH] Recast Evaluator as an object. Handle `goto` inside it.

---
 bin/sixtypical                |   4 +-
 src/sixtypical/evaluator.py   | 277 +++++++++++++++++-----------------
 tests/SixtyPical Execution.md |  18 +++
 3 files changed, 162 insertions(+), 137 deletions(-)

diff --git a/bin/sixtypical b/bin/sixtypical
index 32cc6df..00645dc 100755
--- a/bin/sixtypical
+++ b/bin/sixtypical
@@ -18,7 +18,7 @@ import sys
 import traceback
 
 from sixtypical.parser import Parser
-from sixtypical.evaluator import eval_program
+from sixtypical.evaluator import Evaluator
 from sixtypical.analyzer import analyze_program
 from sixtypical.emitter import Emitter, Byte, Word
 from sixtypical.compiler import Compiler
@@ -88,5 +88,5 @@ if __name__ == '__main__':
                 emitter.serialize(fh)
 
         if options.execute:
-            context = eval_program(program)
+            context = Evaluator().eval_program(program)
             print str(context)
diff --git a/src/sixtypical/evaluator.py b/src/sixtypical/evaluator.py
index 53c3b9d..90b9513 100644
--- a/src/sixtypical/evaluator.py
+++ b/src/sixtypical/evaluator.py
@@ -29,144 +29,151 @@ class Context(object):
         self._store[ref.name] = value
 
 
-def eval_program(program):
-    assert isinstance(program, Program)
-    context = Context()
-    for ref in (REG_A, REG_X, REG_Y, FLAG_Z, FLAG_N, FLAG_V, FLAG_C):
-        context.set(ref, 0)
-    main = None
-    for routine in program.routines:
-        context.set(routine.location, routine)
-        if routine.name == 'main':
-            main = routine
-    eval_routine(main, context)
-    return context
+class Evaluator(object):
 
+    def eval_program(self, program):
+        assert isinstance(program, Program)
+        context = Context()
+        for ref in (REG_A, REG_X, REG_Y, FLAG_Z, FLAG_N, FLAG_V, FLAG_C):
+            context.set(ref, 0)
+        main = None
+        for routine in program.routines:
+            context.set(routine.location, routine)
+            if routine.name == 'main':
+                main = routine
+        self.eval_routine(main, context)
+        return context
 
-def eval_routine(routine, context):
-    assert isinstance(routine, Routine)
-    eval_block(routine.block, context)
+    def eval_routine(self, routine, context):
+        assert isinstance(routine, Routine)
+        self.next_routine = routine
+        while self.next_routine:
+            routine = self.next_routine
+            self.next_routine = None
+            self.eval_block(routine.block, context)
 
+    def eval_block(self, block, context):
+        assert isinstance(block, Block)
+        for i in block.instrs:
+            self.eval_instr(i, context)
+            if self.next_routine:
+                break
 
-def eval_block(block, context):
-    assert isinstance(block, Block)
-    for i in block.instrs:
-        eval_instr(i, context)
+    def eval_instr(self, instr, context):
+        assert isinstance(instr, Instr)
+        opcode = instr.opcode
+        dest = instr.dest
+        src = instr.src
 
-
-def eval_instr(instr, context):
-    assert isinstance(instr, Instr)
-    opcode = instr.opcode
-    dest = instr.dest
-    src = instr.src
-
-    if opcode == 'ld':
-        result = context.get(src)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'st':
-        context.set(dest, context.get(src))
-    elif opcode == 'add':
-        carry = context.get(FLAG_C)
-        val = context.get(src)
-        now = context.get(dest)
-        result = now + val + carry
-        if result > 255:
-            result &= 255
-            context.set(FLAG_C, 1)
+        if opcode == 'ld':
+            result = context.get(src)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'st':
+            context.set(dest, context.get(src))
+        elif opcode == 'add':
+            carry = context.get(FLAG_C)
+            val = context.get(src)
+            now = context.get(dest)
+            result = now + val + carry
+            if result > 255:
+                result &= 255
+                context.set(FLAG_C, 1)
+            else:
+                context.set(FLAG_C, 0)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'sub':
+            carry = context.get(FLAG_C)
+            val = context.get(src)
+            now = context.get(dest)
+            result = now - val - carry
+            if result < 0:
+                result &= 255
+                context.set(FLAG_C, 1)
+            else:
+                context.set(FLAG_C, 0)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'inc':
+            val = context.get(dest)
+            result = (val + 1) & 255
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'dec':
+            val = context.get(dest)
+            result = (val - 1) & 255
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'cmp':
+            val = context.get(src)
+            now = context.get(dest)
+            result = now - val
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            if result < 0:
+                result &= 255
+                context.set(FLAG_C, 1)
+            else:
+                context.set(FLAG_C, 0)
+        elif opcode == 'and':
+            result = context.get(dest) & context.get(src)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'or':
+            result = context.get(dest) | context.get(src)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'xor':
+            result = context.get(dest) ^ context.get(src)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'shl':
+            val = context.get(dest)
+            carry = context.get(FLAG_C)
+            context.set(FLAG_C, 1 if val & 128 else 0)
+            result = ((val << 1) + carry) & 255
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'shr':
+            val = context.get(dest)
+            carry = context.get(FLAG_C)
+            context.set(FLAG_C, 1 if val & 1 else 0)
+            result = (val >> 1) + (carry * 128)
+            context.set(FLAG_Z, 1 if result == 0 else 0)
+            context.set(FLAG_N, 1 if result & 128 else 0)
+            context.set(dest, result)
+        elif opcode == 'call':
+            self.eval_routine(context.get(instr.location), context)
+        elif opcode == 'goto':
+            self.next_routine = context.get(instr.location)
+        elif opcode == 'if':
+            val = context.get(src)
+            test = (val != 0) if not instr.inverted else (val == 0)
+            if test:
+                self.eval_block(instr.block1, context)
+            elif instr.block2:
+                self.eval_block(instr.block2, context)
+        elif opcode == 'repeat':
+            self.eval_block(instr.block, context)
+            while context.get(src) == 0:
+                self.eval_block(instr.block, context)
+        elif opcode == 'copy':
+            context.set(dest, context.get(src))
+            # these are trashed; so could be anything really
+            context.set(REG_A, 0)
+            context.set(FLAG_Z, 0)
+            context.set(FLAG_N, 0)
+        elif opcode == 'with-sei':
+            self.eval_block(instr.block)
         else:
-            context.set(FLAG_C, 0)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'sub':
-        carry = context.get(FLAG_C)
-        val = context.get(src)
-        now = context.get(dest)
-        result = now - val - carry
-        if result < 0:
-            result &= 255
-            context.set(FLAG_C, 1)
-        else:
-            context.set(FLAG_C, 0)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'inc':
-        val = context.get(dest)
-        result = (val + 1) & 255
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'dec':
-        val = context.get(dest)
-        result = (val - 1) & 255
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'cmp':
-        val = context.get(src)
-        now = context.get(dest)
-        result = now - val
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        if result < 0:
-            result &= 255
-            context.set(FLAG_C, 1)
-        else:
-            context.set(FLAG_C, 0)
-    elif opcode == 'and':
-        result = context.get(dest) & context.get(src)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'or':
-        result = context.get(dest) | context.get(src)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'xor':
-        result = context.get(dest) ^ context.get(src)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'shl':
-        val = context.get(dest)
-        carry = context.get(FLAG_C)
-        context.set(FLAG_C, 1 if val & 128 else 0)
-        result = ((val << 1) + carry) & 255
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'shr':
-        val = context.get(dest)
-        carry = context.get(FLAG_C)
-        context.set(FLAG_C, 1 if val & 1 else 0)
-        result = (val >> 1) + (carry * 128)
-        context.set(FLAG_Z, 1 if result == 0 else 0)
-        context.set(FLAG_N, 1 if result & 128 else 0)
-        context.set(dest, result)
-    elif opcode == 'call':
-        eval_routine(context.get(instr.location), context)
-    elif opcode == 'if':
-        val = context.get(src)
-        test = (val != 0) if not instr.inverted else (val == 0)
-        if test:
-            eval_block(instr.block1, context)
-        elif instr.block2:
-            eval_block(instr.block2, context)
-    elif opcode == 'repeat':
-        eval_block(instr.block, context)
-        while context.get(src) == 0:
-            eval_block(instr.block, context)
-    elif opcode == 'copy':
-        context.set(dest, context.get(src))
-        # these are trashed; so could be anything really
-        context.set(REG_A, 0)
-        context.set(FLAG_Z, 0)
-        context.set(FLAG_N, 0)
-    elif opcode == 'with-sei':
-        eval_block(instr.block)
-    else:
-        raise NotImplementedError
+            raise NotImplementedError
diff --git a/tests/SixtyPical Execution.md b/tests/SixtyPical Execution.md
index af3cf1a..1b526d0 100644
--- a/tests/SixtyPical Execution.md	
+++ b/tests/SixtyPical Execution.md	
@@ -420,3 +420,21 @@ Indirect call.
     = x: 200
     = y: 0
     = z: 0
+
+goto.
+
+    | routine bar outputs x trashes z, n {
+    |     ld x, 200
+    | }
+    | 
+    | routine main outputs x trashes a, z, n {
+    |     ld y, 200
+    |     goto bar
+    | }
+    = a: 0
+    = c: 0
+    = n: 1
+    = v: 0
+    = x: 200
+    = y: 200
+    = z: 0