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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Microsoft Public License. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Microsoft Public License, please send an email to
* dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Microsoft Public License.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System.Collections.Generic;
using System.Linq.Expressions;
using Microsoft.Scripting.Utils;
namespace Microsoft.Scripting.Ast {
public sealed class IfStatementBuilder {
private readonly List<IfStatementTest> _clauses = new List<IfStatementTest>();
internal IfStatementBuilder() {
}
public IfStatementBuilder ElseIf(Expression test, params Expression[] body) {
ContractUtils.RequiresNotNullItems(body, "body");
return ElseIf(test, Utils.BlockVoid(body));
}
public IfStatementBuilder ElseIf(Expression test, Expression body) {
ContractUtils.RequiresNotNull(test, "test");
ContractUtils.Requires(test.Type == typeof(bool), "test");
ContractUtils.RequiresNotNull(body, "body");
_clauses.Add(Utils.IfCondition(test, body));
return this;
}
public Expression Else(params Expression[] body) {
ContractUtils.RequiresNotNullItems(body, "body");
return Else(Utils.BlockVoid(body));
}
public Expression Else(Expression body) {
ContractUtils.RequiresNotNull(body, "body");
return BuildConditions(_clauses, body);
}
internal static Expression BuildConditions(IList<IfStatementTest> clauses, Expression @else) {
Expression result = @else != null ? @else : Utils.Empty();
// This should probably be using SwitchExpression to avoid stack
// overflow if we have lots of "else" clauses.
int index = clauses.Count;
while (index-- > 0) {
IfStatementTest ist = clauses[index];
result = Expression.IfThenElse(ist.Test, ist.Body, result);
}
return result;
}
public Expression ToStatement() {
return BuildConditions(_clauses, null);
}
public static implicit operator Expression(IfStatementBuilder builder) {
ContractUtils.RequiresNotNull(builder, "builder");
return builder.ToStatement();
}
}
public partial class Utils {
public static IfStatementBuilder If() {
return new IfStatementBuilder();
}
public static IfStatementBuilder If(Expression test, params Expression[] body) {
return If().ElseIf(test, body);
}
public static IfStatementBuilder If(Expression test, Expression body) {
return If().ElseIf(test, body);
}
public static Expression If(IfStatementTest[] tests, Expression @else) {
ContractUtils.RequiresNotNullItems(tests, "tests");
return IfStatementBuilder.BuildConditions(tests, @else);
}
public static Expression IfThen(Expression test, Expression body) {
return IfThenElse(test, body, null);
}
public static Expression IfThen(Expression test, params Expression[] body) {
return IfThenElse(test, Utils.BlockVoid(body), null);
}
public static Expression IfThenElse(Expression test, Expression body, Expression @else) {
return If(
new IfStatementTest[] {
Utils.IfCondition(test, body)
},
@else
);
}
public static Expression Unless(Expression test, Expression body) {
return IfThenElse(test, Utils.Empty(), body);
}
}
}
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