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Add symbolic constants.
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Chris Pressey
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@ -1,6 +1,12 @@
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History of SixtyPical
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=====================
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0.15
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----
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* Symbolic constants can be defined with the `const` keyword, and can
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be used in most places where literal values can be used.
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0.14
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----
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@ -81,7 +81,6 @@ is probably NP-complete. But doing it adequately is probably not that hard.
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### And at some point...
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* `low` and `high` address operators - to turn `word` type into `byte`.
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* `const`s that can be used in defining the size of tables, etc.
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* Tests, and implementation, ensuring a routine can be assigned to a vector of "wider" type
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* Related: can we simply view a (small) part of a buffer as a byte table? If not, why not?
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* Related: add constant to buffer to get new buffer. (Or to table, but... well, maybe.)
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@ -1,7 +1,7 @@
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SixtyPical
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==========
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This document describes the SixtyPical programming language version 0.14,
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This document describes the SixtyPical programming language version 0.15,
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both its static semantics (the capabilities and limits of the static
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analyses it defines) and its runtime semantics (with reference to the
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semantics of 6502 machine code.)
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@ -555,9 +555,10 @@ The block is always executed as least once.
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Grammar
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-------
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Program ::= {TypeDefn} {Defn} {Routine}.
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Program ::= {ConstDefn | TypeDefn} {Defn} {Routine}.
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ConstDefn::= "const" Ident<new> Const.
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TypeDefn::= "typedef" Type Ident<new>.
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Defn ::= Type Ident<new> [Constraints] (":" Literal | "@" LitWord).
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Defn ::= Type Ident<new> [Constraints] (":" Const | "@" LitWord).
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Type ::= TypeTerm ["table" TypeSize].
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TypeExpr::= "byte"
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| "word"
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@ -573,12 +574,13 @@ Grammar
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| "routine" Ident<new> Constraints (Block | "@" LitWord)
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.
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LocExprs::= LocExpr {"," LocExpr}.
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LocExpr ::= Register | Flag | Literal | Ident.
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LocExpr ::= Register | Flag | Const | Ident.
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Register::= "a" | "x" | "y".
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Flag ::= "c" | "z" | "n" | "v".
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Const ::= Literal | Ident<const>.
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Literal ::= LitByte | LitWord | LitBit.
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LitByte ::= "0" ... "255".
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LitWord ::= "0" ... "65535".
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LitWord ::= ["word"] "0" ... "65535".
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LitBit ::= "on" | "off".
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Block ::= "{" {Instr} "}".
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Instr ::= "ld" LocExpr "," LocExpr ["+" LocExpr]
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@ -598,6 +600,6 @@ Grammar
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| "copy" LocExpr "," LocExpr ["+" LocExpr]
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| "if" ["not"] LocExpr Block ["else" Block]
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| "repeat" Block ("until" ["not"] LocExpr | "forever")
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| "for" LocExpr ("up"|"down") "to" Literal Block
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| "for" LocExpr ("up"|"down") "to" Const Block
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| "with" "interrupts" LitBit Block
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.
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@ -24,6 +24,7 @@ class Parser(object):
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self.symbols = {} # token -> SymEntry
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self.current_statics = {} # token -> SymEntry
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self.typedefs = {} # token -> Type AST
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self.consts = {} # token -> Loc
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for token in ('a', 'x', 'y'):
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self.symbols[token] = SymEntry(None, LocationRef(TYPE_BYTE, token))
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for token in ('c', 'z', 'n', 'v'):
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@ -51,8 +52,11 @@ class Parser(object):
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def program(self):
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defns = []
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routines = []
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while self.scanner.on('typedef'):
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typedef = self.typedef()
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while self.scanner.on('typedef', 'const'):
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if self.scanner.on('typedef'):
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self.typedef()
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if self.scanner.on('const'):
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self.defn_const()
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typenames = ['byte', 'word', 'table', 'vector', 'buffer', 'pointer'] # 'routine',
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typenames.extend(self.typedefs.keys())
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while self.scanner.on(*typenames):
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@ -110,6 +114,15 @@ class Parser(object):
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self.typedefs[name] = type_
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return type_
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def defn_const(self):
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self.scanner.expect('const')
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name = self.defn_name()
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if name in self.consts:
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self.syntax_error('Const "%s" already declared' % name)
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loc = self.const()
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self.consts[name] = loc
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return loc
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def defn(self):
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type_ = self.defn_type()
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name = self.defn_name()
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@ -118,10 +131,9 @@ class Parser(object):
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if self.scanner.consume(':'):
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if isinstance(type_, TableType) and self.scanner.on_type('string literal'):
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initial = self.scanner.token
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else:
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self.scanner.check_type('integer literal')
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initial = int(self.scanner.token)
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self.scanner.scan()
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else:
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initial = self.const().value
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addr = None
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if self.scanner.consume('@'):
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@ -136,21 +148,31 @@ class Parser(object):
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return Defn(self.scanner.line_number, name=name, addr=addr, initial=initial, location=location)
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def literal_int(self):
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self.scanner.check_type('integer literal')
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c = int(self.scanner.token)
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def const(self):
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if self.scanner.token in ('on', 'off'):
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loc = ConstantRef(TYPE_BIT, 1 if self.scanner.token == 'on' else 0)
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self.scanner.scan()
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return loc
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elif self.scanner.on_type('integer literal'):
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value = int(self.scanner.token)
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self.scanner.scan()
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return c
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def literal_int_const(self):
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value = self.literal_int()
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type_ = TYPE_WORD if value > 255 else TYPE_BYTE
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loc = ConstantRef(type_, value)
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return loc
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elif self.scanner.consume('word'):
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loc = ConstantRef(TYPE_WORD, int(self.scanner.token))
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self.scanner.scan()
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return loc
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elif self.scanner.token in self.consts:
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loc = self.consts[self.scanner.token]
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self.scanner.scan()
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return loc
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else:
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self.syntax_error('bad constant "%s"' % self.scanner.token)
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def defn_size(self):
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self.scanner.expect('[')
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size = self.literal_int()
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size = self.const().value
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self.scanner.expect(']')
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return size
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@ -294,16 +316,8 @@ class Parser(object):
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return accum
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def locexpr(self, forward=False):
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if self.scanner.token in ('on', 'off'):
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loc = ConstantRef(TYPE_BIT, 1 if self.scanner.token == 'on' else 0)
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self.scanner.scan()
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return loc
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elif self.scanner.on_type('integer literal'):
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return self.literal_int_const()
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elif self.scanner.consume('word'):
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loc = ConstantRef(TYPE_WORD, int(self.scanner.token))
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self.scanner.scan()
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return loc
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if self.scanner.token in ('on', 'off', 'word') or self.scanner.token in self.consts or self.scanner.on_type('integer literal'):
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return self.const()
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elif forward:
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name = self.scanner.token
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self.scanner.scan()
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@ -387,7 +401,7 @@ class Parser(object):
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else:
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self.syntax_error('expected "up" or "down", found "%s"' % self.scanner.token)
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self.scanner.expect('to')
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final = self.literal_int_const()
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final = self.const()
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block = self.block()
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return For(self.scanner.line_number, dest=dest, direction=direction, final=final, block=block)
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elif self.scanner.token in ("ld",):
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@ -228,6 +228,31 @@ Can't have two typedefs with the same name.
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| }
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? SyntaxError
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Constants.
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| const lives 3
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| const days lives
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| const w1 1000
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| const w2 word 0
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| typedef byte table[days] them
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| byte lark: lives
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| routine main {
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| ld a, lives
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| }
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= ok
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Can't have two constants with the same name.
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| const w1 1000
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| const w1 word 0
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| routine main {
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| }
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? SyntaxError
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Explicit memory address.
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| byte screen @ 1024
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