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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.devtools.build.lib.syntax.SkylarkList.MutableList;
import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* Syntax node for list and tuple literals.
*
* <p>(Note that during evaluation, both list and tuple values are represented by
* java.util.List objects, the only difference between them being whether or not
* they are mutable.)
*/
public final class ListLiteral extends Expression {
/**
* Types of the ListLiteral.
*/
public static enum Kind {LIST, TUPLE}
private final Kind kind;
private final List<Expression> exprs;
private ListLiteral(Kind kind, List<Expression> exprs) {
this.kind = kind;
this.exprs = exprs;
}
public static ListLiteral makeList(List<Expression> exprs) {
return new ListLiteral(Kind.LIST, exprs);
}
public static ListLiteral makeTuple(List<Expression> exprs) {
return new ListLiteral(Kind.TUPLE, exprs);
}
/** A new literal for an empty list, onto which a new location can be specified */
public static ListLiteral emptyList() {
return makeList(Collections.<Expression>emptyList());
}
/**
* Returns the list of expressions for each element of the tuple.
*/
public List<Expression> getElements() {
return exprs;
}
/**
* Returns true if this list is a tuple (a hash table, immutable list).
*/
public boolean isTuple() {
return kind == Kind.TUPLE;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
Printer.printList(sb, exprs, isTuple(), '"');
return sb.toString();
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
List<Object> result = new ArrayList<>();
for (Expression expr : exprs) {
// Convert NPEs to EvalExceptions.
if (expr == null) {
throw new EvalException(getLocation(), "null expression in " + this);
}
result.add(expr.eval(env));
}
if (env.isSkylark()) {
return isTuple() ? Tuple.copyOf(result) : new MutableList(result, env);
} else {
return EvalUtils.makeSequence(result, isTuple());
}
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
void validate(ValidationEnvironment env) throws EvalException {
for (Expression expr : exprs) {
expr.validate(env);
}
}
}
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