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Code Issues Packages Projects Releases 10 Wiki Activity

Collapse Sequence into Block. (#927)

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This commit is contained in:
Jon Meow
2021-11-01 14:59:39 -07:00
committed by GitHub
parent e69ec3f528
commit 904774fbb8
7 changed files with 60 additions and 131 deletions
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executable_semantics/interpreter/interpreter.cpp
+12 -24
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@@ -857,17 +857,20 @@ auto Interpreter::StepStmt() -> Transition {
return UnwindTo{&cast<Continue>(stmt).loop()};
}
case Statement::Kind::Block: {
if (act->pos() == 0) {
const Block& block = cast<Block>(stmt);
if (block.sequence()) {
act->StartScope(Scope(CurrentEnv()));
return Spawn{arena_->New<StatementAction>(*block.sequence())};
} else {
return Done{};
}
} else {
const auto& block = cast<Block>(stmt);
if (act->pos() >= static_cast<int>(block.statements().size())) {
// If the position is past the end of the block, end processing. Note
// that empty blocks immediately end.
return Done{};
}
// Initialize a scope when starting a block.
if (act->pos() == 0) {
act->StartScope(Scope(CurrentEnv()));
}
// Process the next statement in the block. The position will be
// incremented as part of Spawn.
return Spawn{
arena_->New<StatementAction>(block.statements()[act->pos()])};
}
case Statement::Kind::VariableDefinition: {
const auto& definition = cast<VariableDefinition>(stmt);
@@ -962,21 +965,6 @@ auto Interpreter::StepStmt() -> Transition {
const FunctionDeclaration& function = cast<Return>(stmt).function();
return UnwindPast{*function.body(), act->results()[0]};
}
case Statement::Kind::Sequence: {
// { { (s1,s2) :: C, E, F} :: S, H}
// -> { { s1 :: s2 :: C, E, F} :: S, H}
const auto& seq = cast<Sequence>(stmt);
if (act->pos() == 0) {
return Spawn{arena_->New<StatementAction>(&seq.statement())};
} else {
if (seq.next()) {
return Delegate{
arena_->New<StatementAction>(*cast<Sequence>(stmt).next())};
} else {
return Done{};
}
}
}
case Statement::Kind::Continuation: {
CHECK(act->pos() == 0);
// Create a continuation object by creating a frame similar the