Application: gvSIG desktop

package org.gvsig.expressionevaluator.impl.function.programming;

import org.apache.commons.lang3.Range;

import org.gvsig.expressionevaluator.ExpressionBuilder;

import org.gvsig.expressionevaluator.Function;

import org.gvsig.expressionevaluator.Interpreter;

import org.gvsig.expressionevaluator.MutableSymbolTable;

import org.gvsig.expressionevaluator.SymbolTable;

import org.gvsig.expressionevaluator.spi.AbstractFunction;

public class LetFunction extends AbstractFunction {

    public LetFunction() {

        super(Function.GROUP_PROGRAMMING, 

                ExpressionBuilder.FUNCTION_LET, 

            Range.is(2),

            "Assigns the value indicated in the second argument to the variable indicated in the first argument.",

            "SET {{identifier}} = expression",

            new String[]{

                "identifier_name - Name of the variable",

                "value - Value to assign to the variable"

            },

            "Object",

            false

        );

        this.addAlias("SET");

    }

    @Override

    public boolean allowConstantFolding() {

        return false;

    }

    @Override

    public Object call(Interpreter interpreter, Object[] args) throws Exception {

        String name = getStr(args,0);

        Object obj = getObject(args, 1);

        if( name == null ) {

            throw new NullPointerException("A string with a variable name was expected and a null was received");

        }

        SymbolTable symbolTable = interpreter.getSymbolTable();

        if( symbolTable instanceof MutableSymbolTable ) {

            ((MutableSymbolTable)symbolTable).setVar(name, obj);

        } else {

            throw new RuntimeException("A MutableSymbolTable is required for use let function.");

        }

        return obj;

    }

}