r.base.special.SwitchFunction.java Source code

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Here is the source code for r.base.special.SwitchFunction.java

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/*
 * R : A Computer Language for Statistical Data Analysis
 * Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 * Copyright (C) 1997--2008  The R Development Core Team
 * Copyright (C) 2003, 2004  The R Foundation
 * Copyright (C) 2010 bedatadriven
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package r.base.special;

import com.google.common.collect.Iterables;
import r.lang.*;
import r.lang.exception.EvalException;

public class SwitchFunction extends SpecialFunction {

    @Override
    public String getName() {
        return "switch";
    }

    @Override
    public SEXP apply(Context context, Environment rho, FunctionCall call, PairList args) {
        EvalException.check(call.length() > 1, "argument \"EXPR\" is missing");

        SEXP expr = context.evaluate(call.getArgument(0), rho);
        EvalException.check(expr.length() == 1, "EXPR must return a length 1 vector");

        PromisePairList branchPromises = (PromisePairList) context.evaluate(call.getArgument(1), rho);
        Iterable<PairList.Node> branches = branchPromises.nodes();

        if (expr instanceof StringVector) {
            String name = ((StringVector) expr).getElementAsString(0);
            if (StringVector.isNA(name)) {
                context.setInvisibleFlag();
                return Null.INSTANCE;
            }
            SEXP partialMatch = null;
            int partialMatchCount = 0;
            for (PairList.Node node : branches) {
                if (node.hasTag()) {
                    String branchName = node.getTag().getPrintName();
                    if (branchName.equals(name)) {
                        return context.evaluate(nextNonMissing(node), rho);
                    } else if (branchName.startsWith(name)) {
                        partialMatch = nextNonMissing(node);
                        partialMatchCount++;
                    }
                }
            }
            if (partialMatchCount == 1) {
                return context.evaluate(partialMatch, rho);
            } else if (Iterables.size(branches) > 0) {
                PairList.Node last = Iterables.getLast(branches);
                if (!last.hasTag()) {
                    return context.evaluate(last.getValue(), rho);
                }
            }

        } else if (expr instanceof AtomicVector) {
            int branchIndex = ((AtomicVector) expr).getElementAsInt(0);
            if (branchIndex >= 1 && branchIndex <= Iterables.size(branches)) {
                return context.evaluate(Iterables.get(branches, branchIndex - 1).getValue(), rho);
            }
        }

        return Null.INSTANCE;
    }

    private SEXP nextNonMissing(PairList.Node node) {
        do {
            if (node.getValue() != Symbol.MISSING_ARG) {
                return node.getValue();
            }
            if (!node.hasNextNode()) {
                return Null.INSTANCE;
            }
            node = node.getNextNode();
        } while (true);
    }
}