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Code Issues Packages Projects Releases 10 Wiki Activity

Clean up ManualTransition for match statements. (#773)

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This commit is contained in:
Geoff Romer
2021-08-30 16:47:26 -07:00
committed by GitHub
parent 49013ae1cc
commit 3058fb99aa
2 changed files with 23 additions and 29 deletions
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executable_semantics/interpreter/interpreter.cpp
+22 -28
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@@ -722,11 +722,12 @@ static auto IsWhileAct(Ptr<Action> act) -> bool {
}
}
static auto IsBlockAct(Ptr<Action> act) -> bool {
static auto HasLocalScope(Ptr<Action> act) -> bool {
switch (act->Tag()) {
case Action::Kind::StatementAction:
switch (cast<StatementAction>(*act).Stmt()->Tag()) {
case Statement::Kind::Block:
case Statement::Kind::Match:
return true;
default:
return false;
@@ -746,12 +747,13 @@ auto Interpreter::StepStmt() -> Transition {
llvm::outs() << " --->\n";
}
switch (stmt->Tag()) {
case Statement::Kind::Match:
case Statement::Kind::Match: {
const auto& match_stmt = cast<Match>(*stmt);
if (act->Pos() == 0) {
// { { (match (e) ...) :: C, E, F} :: S, H}
// -> { { e :: (match ([]) ...) :: C, E, F} :: S, H}
return Spawn{
global_arena->New<ExpressionAction>(cast<Match>(*stmt).Exp())};
frame->scopes.Push(global_arena->New<Scope>(CurrentEnv()));
return Spawn{global_arena->New<ExpressionAction>(match_stmt.Exp())};
} else {
// Regarding act->Pos():
// * odd: start interpreting the pattern of a clause
@@ -763,11 +765,12 @@ auto Interpreter::StepStmt() -> Transition {
// * 2: the pattern for clause 1
// * ...
auto clause_num = (act->Pos() - 1) / 2;
if (clause_num >=
static_cast<int>(cast<Match>(*stmt).Clauses()->size())) {
if (clause_num >= static_cast<int>(match_stmt.Clauses()->size())) {
DeallocateScope(frame->scopes.Top());
frame->scopes.Pop();
return Done{};
}
auto c = cast<Match>(*stmt).Clauses()->begin();
auto c = match_stmt.Clauses()->begin();
std::advance(c, clause_num);
if (act->Pos() % 2 == 1) {
@@ -780,31 +783,20 @@ auto Interpreter::StepStmt() -> Transition {
auto pat = act->Results()[clause_num + 1];
std::optional<Env> matches = PatternMatch(pat, v, stmt->SourceLoc());
if (matches) { // we have a match, start the body
Env values = CurrentEnv();
std::list<std::string> vars;
// Ensure we don't process any more clauses.
act->SetPos(2 * match_stmt.Clauses()->size() + 1);
for (const auto& [name, value] : *matches) {
values.Set(name, value);
vars.push_back(name);
frame->scopes.Top()->values.Set(name, value);
frame->scopes.Top()->locals.push_back(name);
}
frame->scopes.Push(global_arena->New<Scope>(values, vars));
auto body_act = global_arena->New<StatementAction>(
global_arena->New<Block>(stmt->SourceLoc(), c->second));
body_act->IncrementPos();
frame->todo.Pop(1);
frame->todo.Push(body_act);
frame->todo.Push(global_arena->New<StatementAction>(c->second));
return ManualTransition{};
return Spawn{global_arena->New<StatementAction>(c->second)};
} else {
// this case did not match, moving on
int next_clause_num = act->Pos() / 2;
if (next_clause_num ==
static_cast<int>(cast<Match>(*stmt).Clauses()->size())) {
return Done{};
}
return RunAgain{};
}
}
}
}
case Statement::Kind::While:
if (act->Pos() % 2 == 0) {
// { { (while (e) s) :: C, E, F} :: S, H}
@@ -1050,7 +1042,8 @@ class Interpreter::DoTransition {
void operator()(const Spawn& spawn) {
Ptr<Frame> frame = interpreter->stack.Top();
frame->todo.Top()->IncrementPos();
Ptr<Action> action = frame->todo.Top();
action->SetPos(action->Pos() + 1);
frame->todo.Push(spawn.child);
}
@@ -1061,13 +1054,14 @@ class Interpreter::DoTransition {
}
void operator()(const RunAgain&) {
interpreter->stack.Top()->todo.Top()->IncrementPos();
Ptr<Action> action = interpreter->stack.Top()->todo.Top();
action->SetPos(action->Pos() + 1);
}
void operator()(const UnwindTo& unwind_to) {
Ptr<Frame> frame = interpreter->stack.Top();
while (frame->todo.Top() != unwind_to.new_top) {
if (IsBlockAct(frame->todo.Top())) {
if (HasLocalScope(frame->todo.Top())) {
interpreter->DeallocateScope(frame->scopes.Top());
frame->scopes.Pop();
}