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JSimpleDB classes for parsing Java expressions.

There is a newer version: 3.6.1


/*
 * Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
 */

package org.jsimpledb.parse.func;

import com.google.common.collect.Iterables;

import org.jsimpledb.SessionMode;
import org.jsimpledb.parse.ParseSession;
import org.jsimpledb.parse.expr.AbstractValue;
import org.jsimpledb.parse.expr.EvalException;
import org.jsimpledb.parse.expr.Value;

@Function(modes = { SessionMode.KEY_VALUE, SessionMode.CORE_API, SessionMode.JSIMPLEDB })
public class ConcatFunction extends SimpleFunction {

    public ConcatFunction() {
        super("concat", 1, 1);
    }

    @Override
    public String getHelpSummary() {
        return "Concatenates the Iterables within an Iterable";
    }

    @Override
    public String getUsage() {
        return "concat(items)";
    }

    @Override
    public String getHelpDetail() {
        return "The concat() function takes an argument which must be an Iterable of Iterables (i.e., an instance of"
          + " Iterable>), and returns a new Iterable which is the concatenation of the inner Iterables.";
    }

    @Override
    protected Value apply(ParseSession session, Value[] params) {
        final Value value = params[0];
        return new AbstractValue() {
            @Override
            public Object get(final ParseSession session) {
                return Iterables.concat(Iterables.transform((Iterable)value.checkType(session, "concat()", Iterable.class),
                  new com.google.common.base.Function>() {
                    @Override
                    public Iterable apply(Object item) {
                        if (item == null)
                            throw new EvalException("concat() operation encountered null Iterable");
                        if (!(item instanceof Iterable)) {
                            throw new EvalException("concat() operation encountered non-Iterable value of type "
                              + item.getClass().getName());
                        }
                        return (Iterable)item;
                    }
                }));
            }
        };
    }
}