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-- Copyright (C) 2011, Gabriel Dos Reis.
-- All rights reserved.
--
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are
-- met:
--
-- - Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
--
-- - Redistributions in binary form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in
-- the documentation and/or other materials provided with the
-- distribution.
--
-- - Neither the name of OpenAxiom. nor the names of its contributors
-- may be used to endorse or promote products derived from this
-- software without specific prior written permission.
--
-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
-- IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
-- TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
-- PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
-- OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
-- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
-- PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
-- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--
--%
--% Author: Gabriel Dos Reis
--%
import sys_-utility
namespace BOOT
module lexing
--%
--% Token abstract datatype.
--% Operational semantics:
--% structure Token ==
--% Record(symbol: Identifier, type: TokenType, nonBlank?: Boolean)
--%
--% type in '(NUMBER IDENTIFIER SPECIAL_-CHAR)
--% nonBlank? if token is not preceded by a blank.
--%
makeToken(sym == nil, typ == nil, blnk? == true) ==
[sym,typ,blnk?]
macro copyToken t ==
copyList t
macro tokenSymbol t ==
first t
macro tokenType t ==
second t
macro tokenNonblank? t ==
third t
++ Last seen token
$priorToken := makeToken()
++ Is there no blank in front of current token?
$nonblank := true
++ First token in input stream
$currentToken := makeToken()
++ Next token in input stream
$nextToken := makeToken()
++ Number of token in the buffer (0, 1, 2)
$validTokens := 0
tokenInstall(sym,typ,tok,nonblank == true) ==
tokenSymbol(tok) := sym
tokenType(tok) := typ
tokenNonblank?(tok) := nonblank
tok
tryGetToken tok ==
GET_-BOOT_-TOKEN tok =>
$validTokens := $validTokens + 1
tok
nil
++ Returns the current token or gets a new one if necessary
currentToken() ==
$validTokens > 0 => $currentToken
tryGetToken $currentToken
++ Returns the token after the current token, or nil if there is none after
nextToken() ==
currentToken()
$validTokens > 1 => $nextToken
tryGetToken $nextToken
matchToken(tok,typ,sym == false) ==
tok ~= nil and symbolEq?(tokenType tok,typ) and
(sym = nil or symbolEq?(sym,tokenSymbol tok)) and tok
++ Return the current token if it has type `typ', and possibly the
++ same spelling as `sym'.
matchCurrentToken(typ,sym == nil) ==
matchToken(currentToken(),typ,sym)
++ Return the next token if it has type `typ;, and possibly the same
++ spelling as `sym'.
matchNextToken(typ,sym == nil) ==
matchToken(nextToken(),typ,sym)
++ Makes the next token be the current token.
advanceToken() ==
$validTokens = 0 => tryGetToken $currentToken
$validTokens = 1 =>
$validTokens := $validTokens - 1
$priorToken := copyToken $currentToken
tryGetToken $currentToken
$validTokens = 2 =>
$priorToken := copyToken $currentToken
$currentToken := copyToken $nextToken
$validTokens := $validTokens - 1
nil
makeSymbolOf tok ==
tok = nil => nil
tokenSymbol tok = nil => nil
char? tokenSymbol tok => makeSymbol charString tokenSymbol tok
tokenSymbol tok
currentSymbol() ==
makeSymbolOf currentToken()
--%
--% Stack abstract datatype.
--% Operational semantics:
--% structure Stack ==
--% Record(store: List T, size: Integer, top: T, updated?: Boolean)
++ Construct a new stack
makeStack() ==
[nil,0,nil,false]
macro stackStore st ==
first st
macro stackSize st ==
second st
macro stackTop st ==
third st
macro stackUpdated? st ==
fourth st
stackLoad!(l,st) ==
stackStore(st) := l
stackSize(st) := #l
stackTop(st) := first l
stackClear! st ==
stackStore(st) := nil
stackSize(st) := 0
stackTop(st) := nil
stackUpdated?(st) := false
stackPush!(x,st) ==
stackStore(st) := [x,:stackStore st]
stackTop(st) := x
stackSize(st) := stackSize st + 1
stackUpdated?(st) := true
stackPop! st ==
y := first stackStore st
stackStore(st) := rest stackStore st
stackSize(st) := stackSize st - 1
if stackStore st ~= nil then
stackTop(st) := first stackStore st
y
--%
--% Parsing reduction stack
--%
--% Abstractly;
--% structure Reduction == Record(rule: RuleName, value: ParseTree)
--%
makeReduction(p == nil,v == nil) ==
[p,v]
macro reductionRule r ==
first r
macro reductionValue r ==
second r
++ stack of results of reduced productions
$reduceStack := makeStack()
pushReduction(rn,pt) ==
stackPush!(makeReduction(rn,pt),$reduceStack)
popReduction() ==
stackPop! $reduceStack
reduceStackClear() ==
stackClear! $reduceStack
popStack1() ==
reductionValue popReduction()
popStack2() ==
r1 := popReduction()
r2 := popReduction()
stackPush!(r1,$reduceStack)
reductionValue r2
popStack3() ==
r1 := popReduction()
r2 := popReduction()
r3 := popReduction()
stackPush!(r2,$reduceStack)
stackPush!(r1,$reduceStack)
reductionValue r3
popStack4() ==
r1 := popReduction()
r2 := popReduction()
r3 := popReduction()
r4 := popReduction()
stackPush!(r3,$reduceStack)
stackPush!(r2,$reduceStack)
stackPush!(r1,$reduceStack)
reductionValue r4
nthStack n ==
reductionValue stackStore($reduceStack).(n - 1)
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