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This commit is contained in:
Calum Grant
2024-05-17 17:00:00 +01:00
parent b200caba1b
commit faf480c995
1 changed files with 101 additions and 106 deletions
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207
cpp/ql/src/experimental/parsing/glr.qll
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@@ -1,16 +1,15 @@
/*
GLR parser framework.
This is purely for fun.
* GLR parser framework.
* This is purely for fun.
*/
signature string grammar();
signature string input(int i);
// A GLR parser
module GLR<grammar/0 g> {
// We need to add a special rule that includes the end of file symbol $
// We need to add a special rule that includes the end of file symbol $
string initialRule() { result = "Start_ -> G $" }
// Gets the left hand side of a rule - for internal use
@@ -75,7 +74,7 @@ module GLR<grammar/0 g> {
Eof() { this = "$" }
}
Terminal follows(Rule rule, int dot, Terminal lookahead) {
private Terminal follows(Rule rule, int dot, Terminal lookahead) {
dot >= 0 and
(
dot + 1 = rule.getLength() and lookahead = result
@@ -87,7 +86,7 @@ module GLR<grammar/0 g> {
}
// Modify the idea of a transition so that we don't need to compute the closure
predicate transition(
private predicate transition(
Rule rule1, int dot1, Terminal lookahead1, Symbol symbol, Rule rule2, int dot2,
Terminal lookahead2
) {
@@ -104,7 +103,7 @@ module GLR<grammar/0 g> {
bindingset[dot, lookahead]
string itemToString(Rule rule, int dot, Terminal lookahead) {
// item(rule, dot, lookahead) and
// item(rule, dot, lookahead) and
result =
rule.getLhs() + " -> " + concat(int i | i in [0 .. dot - 1] | rule.getRhs(i) + " " order by i)
+ ". " +
@@ -120,17 +119,6 @@ module GLR<grammar/0 g> {
concat(int i | i in [dot .. rule.getLength() - 1] | rule.getRhs(i) + " " order by i)
}
class KernelItem extends string {
Rule rule;
int dot;
KernelItem() { this = kernelItem(rule, dot) }
}
class InitialItem extends KernelItem {
InitialItem() { this = kernelItem(initialRule(), 0) }
}
predicate initialState(Rule rule, int dot, Terminal lookahead) {
rule = initialRule() and dot = 0 and lookahead = "$"
}
@@ -188,39 +176,39 @@ module GLR<grammar/0 g> {
// In this state, when the lookahead symbol is `s`, we can shift to `result`
State shift(Terminal s) { result = this.getTransition(s) }
// In this state, when the lookahead symbol is `s`, we can reduce rule `result`
Rule reduce(Terminal s)
{
this.hasItem(result, result.getLength(), s)
}
// In this state, when the lookahead symbol is `s`, we can reduce rule `result`
Rule reduce(Terminal s) { this.hasItem(result, result.getLength(), s) }
// This state has a reduce/reduce conflict, given by the possible shift to `state` or reduce by `rule`
predicate shiftReduceConflict(Terminal s, State state, Rule rule)
{
predicate shiftReduceConflict(Terminal s, State state, Rule rule) {
this.shift(s) = state and this.reduce(s) = rule
}
// This state has a reduce/reduce conflict, given by the possible reduce by `rule1` or `rule2`
predicate reduceReduceConflict(Terminal s, Rule rule1, Rule rule2)
{
this.reduce(s) = rule1 and this.reduce(s) = rule2 and rule1!=rule2
predicate reduceReduceConflict(Terminal s, Rule rule1, Rule rule2) {
this.reduce(s) = rule1 and this.reduce(s) = rule2 and rule1 != rule2
}
predicate hasClosure(Rule rule, int dot, Terminal lookahead)
{
predicate hasClosure(Rule rule, int dot, Terminal lookahead) {
this.hasItem(rule, dot, lookahead)
or
exists(Rule rule0, int dot0, Terminal lookahead0 |
this.hasClosure(rule0, dot0, lookahead0) and
rule.getLhs() = rule0.getRhs(dot0) and dot = 0 and lookahead = follows(rule0, dot0, lookahead0) // ?? Is this a problem
rule.getLhs() = rule0.getRhs(dot0) and
dot = 0 and
lookahead = follows(rule0, dot0, lookahead0)
)
}
string getClosureString() {
result = concat(string s |
exists(Rule rule, int dot, Terminal lookahead | this.hasClosure(rule, dot, lookahead) |
s = itemToString(rule, dot, lookahead)) | s + "; "
)
result =
concat(string s |
exists(Rule rule, int dot, Terminal lookahead | this.hasClosure(rule, dot, lookahead) |
s = itemToString(rule, dot, lookahead)
)
|
s + "; "
)
}
}
@@ -228,78 +216,84 @@ module GLR<grammar/0 g> {
InitialState() { this = getInitialState(_, _, _) }
}
module GLRparser<input/1 i>
{
module GLRparser<input/1 i> {
// We need to insert $ at the end of the input
string getInputToken(int inputPosition) {
result = i(inputPosition) or
string getInputToken(int inputPosition) {
result = i(inputPosition)
or
inputPosition = max(int p | exists(i(p))) and result = "$"
}
/*
The parse stack implements a linked list where the "previous" column is the previous node on the stack.
With reductions `TReduce` on the stack, `skip()` skips large chunks of the stack.
* The parse stack implements a linked list where the "previous" column is the previous node on the stack.
* With reductions `TReduce` on the stack, `skip()` skips large chunks of the stack.
*/
newtype Stack =
TEmpty()
or
TShift(int position, State state, Symbol terminal, ParseNode previous)
{
position = previous.getInputPosition() + 1 and
terminal = getInputToken(position-1) and
state = previous.getState().shift(terminal)
}
or
TReduce(int position, State state, Rule rule, ParseNode previous)
{
position = previous.getInputPosition() and
rule = previous.getState().reduce(getInputToken(position)) and
state = previous.skip(rule.getLength()).getState().goto(rule.getLhs())
}
abstract class ParseNode extends Stack
{
newtype Stack =
TEmpty() or
TShift(int position, State state, Symbol terminal, ParseNode previous) {
position = previous.getInputPosition() + 1 and
terminal = getInputToken(position - 1) and
state = previous.getState().shift(terminal)
} or
TReduce(int position, State state, Rule rule, ParseNode previous) {
position = previous.getInputPosition() and
rule = previous.getState().reduce(getInputToken(position)) and
state = previous.skip(rule.getLength()).getState().goto(rule.getLhs())
}
abstract class ParseNode extends Stack {
language[monotonicAggregates]
abstract string toString();
abstract int getInputPosition();
abstract State getState();
abstract ParseNode getPrevious();
abstract Symbol getSymbol();
string debugString()
{
result = this.toString() + "->" + this.getPrevious().debugString()
}
ParseNode skip(int i) // ?? Member
{
i=0 and result = this
or i>0 and result = this.getPrevious().skip(i-1)
abstract int getInputPosition();
abstract State getState();
abstract ParseNode getPrevious();
abstract Symbol getSymbol();
string debugString() { result = this.toString() + "->" + this.getPrevious().debugString() }
ParseNode skip(int i) {
i = 0 and result = this
or
i > 0 and result = this.getPrevious().skip(i - 1)
}
}
class EmptyNode extends ParseNode, TEmpty
{
class EmptyNode extends ParseNode, TEmpty {
override string toString() { result = "Empty" }
override int getInputPosition() { result = 0 }
override State getState() { result instanceof InitialState }
override ParseNode getPrevious() { none() }
override Symbol getSymbol() { none() }
override string debugString() { result = "ø" }
}
class TerminalNode extends ParseNode, TShift
{
class TerminalNode extends ParseNode, TShift {
int position;
State state;
Terminal terminal;
ParseNode previous;
TerminalNode() { this = TShift(position, state, terminal, previous) }
override string toString() { result = terminal + "@" + position } // + " state " + state.getNumber()}
override string debugString() { result = terminal + "@" + position + " state " + state.getNumber() + "->" + previous.debugString()}
override string toString() { result = terminal + "@" + position }
override string debugString() {
result =
terminal + "@" + position + " state " + state.getNumber() + "->" + previous.debugString()
}
override State getState() { result = state }
override ParseNode getPrevious() { result = previous }
override int getInputPosition() { result = position }
@@ -307,8 +301,7 @@ module GLR<grammar/0 g> {
override Symbol getSymbol() { result = terminal }
}
class NonTerminalNode extends ParseNode, TReduce
{
class NonTerminalNode extends ParseNode, TReduce {
int position;
State state;
Rule rule;
@@ -317,55 +310,57 @@ module GLR<grammar/0 g> {
NonTerminalNode() { this = TReduce(position, state, rule, previous) }
language[monotonicAggregates]
override string toString() { result = rule + "@" + position // + " state " + state.getNumber()
override string toString() {
result = rule + "@" + position
}
override State getState() { result = state }
override ParseNode getPrevious() { result = previous.skip(rule.getLength()) }
override int getInputPosition() { result = position }
override Symbol getSymbol() { result = rule.getLhs() }
ParseNode getChild(int i)
{
ParseNode getChild(int i) {
i in [0 .. rule.getLength() - 1] and
result = previous.skip(rule.getLength() - i-1)
}
result = previous.skip(rule.getLength() - i - 1)
}
}
class Root extends NonTerminalNode
{
class Root extends NonTerminalNode {
Root() { rule.getLhs() = "G" }
}
predicate dumpNodes(ParseNode node, int position, State state, string closure, int stateNumber, string debug)
{
position = node.getInputPosition() and state = node.getState() and stateNumber = state.getNumber() and
closure = state.getClosureString() and debug = node.debugString()
predicate dumpNodes(
ParseNode node, int position, State state, string closure, int stateNumber, string debug
) {
position = node.getInputPosition() and
state = node.getState() and
stateNumber = state.getNumber() and
closure = state.getClosureString() and
debug = node.debugString()
}
predicate tree(NonTerminalNode node, int i, ParseNode child)
{
node.getChild(i) = child
}
predicate tree(NonTerminalNode node, int i, ParseNode child) { node.getChild(i) = child }
}
predicate actionTable(int state, string closure, Symbol symbol, string action)
{
exists(State s | s.getNumber() = state and closure = s.getClosureString() |
if exists(s.shift(symbol)) then action = "shift to state " + s.shift(symbol).getNumber()
else if exists(s.reduce(symbol)) then action = "reduce by rule " + s.reduce(symbol)
else none()
predicate actionTable(int state, string closure, Symbol symbol, string action) {
exists(State s | s.getNumber() = state and closure = s.getClosureString() |
if exists(s.shift(symbol))
then action = "shift to state " + s.shift(symbol).getNumber()
else
if exists(s.reduce(symbol))
then action = "reduce by rule " + s.reduce(symbol)
else none()
)
}
predicate gotoTable(int state, string closure, NonTerminal symbol, int nextState)
{
exists(State s | s.getNumber() = state and closure = s.getClosureString() |
predicate gotoTable(int state, string closure, NonTerminal symbol, int nextState) {
exists(State s | s.getNumber() = state and closure = s.getClosureString() |
nextState = s.goto(symbol).getNumber()
)
}
}
string grammar1() { result = ["G -> E", "E -> x", "E -> E x"] }