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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.syntax;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.syntax.FlowStatement.FlowException;
import java.util.List;
/**
* Syntax node for a for loop statement.
*/
public final class ForStatement extends Statement {
private final LValue variable;
private final Expression collection;
private final ImmutableList<Statement> block;
/**
* Constructs a for loop statement.
*/
ForStatement(Expression variable, Expression collection, List<Statement> block) {
this.variable = new LValue(Preconditions.checkNotNull(variable));
this.collection = Preconditions.checkNotNull(collection);
this.block = ImmutableList.copyOf(block);
}
public LValue getVariable() {
return variable;
}
public Expression getCollection() {
return collection;
}
public ImmutableList<Statement> block() {
return block;
}
@Override
public String toString() {
// TODO(bazel-team): if we want to print the complete statement, the function
// needs an extra argument to specify indentation level.
return "for " + variable + " in " + collection + ": ...\n";
}
@Override
void doExec(Environment env) throws EvalException, InterruptedException {
Object o = collection.eval(env);
Iterable<?> col = EvalUtils.toIterable(o, getLocation());
int i = 0;
for (Object it : ImmutableList.copyOf(col)) {
variable.assign(env, getLocation(), it);
try {
for (Statement stmt : block) {
stmt.exec(env);
}
} catch (FlowException ex) {
if (ex.mustTerminateLoop()) {
return;
}
}
i++;
}
// TODO(bazel-team): This should not happen if every collection is immutable.
if (i != EvalUtils.size(col)) {
throw new EvalException(getLocation(),
String.format("Cannot modify '%s' during during iteration.", collection.toString()));
}
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
void validate(ValidationEnvironment env) throws EvalException {
if (env.isTopLevel()) {
throw new EvalException(getLocation(), "'For' is not allowed as a top level statement");
}
env.enterLoop();
try {
// TODO(bazel-team): validate variable. Maybe make it temporarily readonly.
collection.validate(env);
variable.validate(env, getLocation());
for (Statement stmt : block) {
stmt.validate(env);
}
} finally {
env.exitLoop(getLocation());
}
}
}
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