From d815e05e0ce713d8d59da35b42ccf61141f67750 Mon Sep 17 00:00:00 2001
From: Chris Pressey <cpressey@catseye.tc>
Date: Thu, 8 Mar 2018 16:54:12 +0000
Subject: [PATCH] Syntax for "open-faced for loop".

---
 src/sixtypical/ast.py      |  5 +++++
 src/sixtypical/parser.py   | 23 +++++++++++++++++++----
 tests/SixtyPical Syntax.md | 16 ++++++++++++++++
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/src/sixtypical/ast.py b/src/sixtypical/ast.py
index 0ab9f33..2029173 100644
--- a/src/sixtypical/ast.py
+++ b/src/sixtypical/ast.py
@@ -83,5 +83,10 @@ class Repeat(Instr):
     child_attrs = ('block',)
 
 
+class For(Instr):
+    value_attrs = ('dest', 'direction', 'final')
+    child_attrs = ('block',)
+
+
 class WithInterruptsOff(Instr):
     child_attrs = ('block',)
diff --git a/src/sixtypical/parser.py b/src/sixtypical/parser.py
index 4caf862..061ba03 100644
--- a/src/sixtypical/parser.py
+++ b/src/sixtypical/parser.py
@@ -1,6 +1,6 @@
 # encoding: UTF-8
 
-from sixtypical.ast import Program, Defn, Routine, Block, SingleOp, If, Repeat, WithInterruptsOff
+from sixtypical.ast import Program, Defn, Routine, Block, SingleOp, If, Repeat, For, WithInterruptsOff
 from sixtypical.model import (
     TYPE_BIT, TYPE_BYTE, TYPE_WORD,
     RoutineType, VectorType, TableType, BufferType, PointerType,
@@ -136,11 +136,15 @@ class Parser(object):
 
         return Defn(self.scanner.line_number, name=name, addr=addr, initial=initial, location=location)
 
+    def literal_int(self):
+         self.scanner.check_type('integer literal')
+         c = int(self.scanner.token)
+         self.scanner.scan()
+         return c
+
     def defn_size(self):
         self.scanner.expect('[')
-        self.scanner.check_type('integer literal')
-        size = int(self.scanner.token)
-        self.scanner.scan()
+        size = self.literal_int()
         self.scanner.expect(']')
         return size
 
@@ -372,6 +376,17 @@ class Parser(object):
             else:
                 self.scanner.expect('forever')
             return Repeat(self.scanner.line_number, src=src, block=block, inverted=inverted)
+        elif self.scanner.consume('for'):
+            dest = self.locexpr()
+            if self.scanner.consume('downto'):
+                direction = -1
+            elif self.scanner.consume('upto'):
+                direction = 1
+            else:
+                self.syntax_error('expected "upto" or "downto", found "%s"' % self.scanner.token)
+            final = self.literal_int()
+            block = self.block()
+            return For(self.scanner.line_number, dest=dest, direction=direction, final=final, block=block)
         elif self.scanner.token in ("ld",):
             # the same as add, sub, cmp etc below, except supports an indlocexpr for the src
             opcode = self.scanner.token
diff --git a/tests/SixtyPical Syntax.md b/tests/SixtyPical Syntax.md
index a434345..29bd84b 100644
--- a/tests/SixtyPical Syntax.md	
+++ b/tests/SixtyPical Syntax.md	
@@ -131,6 +131,22 @@ Repeat with not
     | }
     = ok
 
+Basic "open-faced for" loops, up and down.
+
+    | byte table[256] tab
+    | 
+    | routine foo trashes a, x, c, z, v {
+    |     ld x, 0
+    |     for x upto 15 {
+    |         ld a, tab + x
+    |     }
+    |     ld x, 15
+    |     for x downto 0 {
+    |         ld a, tab + x
+    |     }
+    | }
+    = ok
+
 User-defined memory addresses of different types.
 
     | byte byt