Calculator

• no priority
• no associativity
• the heap for computing the result is the heap of the recursive calls.

First version

• The interface Operator describes the methods necessary for an operator : get its symbol, its arity and evaluate a well-formed expression from this operator. .
• The class Operators gives certain usual operators as constants.
• The class SyntaxErrorException represents the exceptions due to a syntax error in an expression.
• The class Caculator allows to evaluate expressions, both from the standard input or an input file. The result may be given on the standard ouput or in an output file. This class specifically uses an instance of java.io.StreamTokenizer for the partition of the expressions in tokens.

Version with dynamic loading of operators

• In this version, the class Calculator has been cleaned, in order to separate the evaluation from the inputs/ouputs.
• The management of the inputs/ouputs has been moved to a class Calculators, which contains only class methods.
• The class Calculator has been extended into a class CalculatorWithPlugins, in which the operators are loaded from a directory given as parameter (instead of being loaded from a static array). This class specifically uses an instance of java.lang.ClassLoader.
  
• The classes Operator, Operators and SyntaxErrorException remain unchanged.
• The classes for operators, (files .class) are now in a directory named "plugins". These files are obtained from sources contained in a directory named "pluginsSrc".
• The main method of this version is now in a class outside the package calculator : DynamicCalculator.
  

1. ask to create a project with separated sources and binaries :
   
   • in the first dialog, click on the item  create separate source and output folders,
   • choose next,
   • in the second dialog, click on the item allow output folders for source folders.
2. create a second source directory, for example pluginsSrc :
   
   • use the command New from the menu File (menu bar or right click), then choose Source Folder, the project under examination being selected.
     
3. create a directory for the binaries obtained from the sources of the directory pluginsSrc :
   
   • click on the directory pluginsSrc with the right button, then select in the menu Build Path the item Configure Ouput Folder ... then choose Specific Ouput Folder and enter the wanted name, for example plugins.