Examples of sunlabs.brazil.util.Calculator

sunlabs.brazil.util.Calculator

Calculator implements a simple arithmetic expression evaluator. It can evaluate typical expressions with the "normal" operators and precedence. Formally, the BNF for the supported grammar is:

 <stmt>    ::= <var> = <expr> | <expr> <expr>    ::= <rexpr> | <expr> <bool op> <rexpr> <bool op> ::= && | <or> <or>      ::= || <rexpr>   ::= <aexpr> | <rexpr> <rel op> <aexpr> <rel op>  ::= < | <= | > | >= | == | != <aexpr>   ::= <term> | <aexpr> <add op> <term> <add op>  ::= + | - <term>    ::= <factor> | <term> <mult op> <factor> <mult op> ::= * | / | % <factor>  ::= <var> | <num> | ! <factor> | ( <expr> ) <var>     ::= <letter> | <var> <var2> <var2>    ::= <letterordigit> | . | _ <num>     ::= <unum> | + <unum> | - <unum> <unum>    ::= <int> | <int> . | <int> . <int> | . <int> <int>     ::= <digit> | <int> <digit>

A <letter> is defined as a Java char for which Char.isLetter(char) is true. A <letterordigit> is defined as a Java char for which Char.isLetterOrDigit(char) is true. A digit is defined as a Java char for which Char.isDigit(char) is true.

Values for <var> are looked up in the supplied Dictionary. If <var> can not be found, it is assumed to have the value zero. If the value found is "true" or "yes" (case insensitive), it is assumed to be one. Similarly, if the value found is "false" or "no", it is assumed to be zero. Assignment to <var> stores the computed value in the same Dictionary.

The period in <unum>, if there is one, must be immediately adjacent to surrounding <int>s. @author Steve Drach <drach@sun.com> @version 2.3

     * This constructor creates a <code>Calculator</code> instance with
     * this instance of <code>ExprProps</code> as it's symbol table.
     */
    public ExprProps() {
  super();
  c = new Calculator(this);
    }

     *
     * @param defaults                the defaults
     */
    public ExprProps(Properties defaults) {
  super(defaults);
  c = new Calculator(this);
    }

   * for example, after Calculator is initialized.  Save request so
         * a new request.props can be passed to each call to
         * Calculator.getValue().
         */
  this.request = request;
  c = new Calculator(request.props);
    }

     * @param defaults                the defaults
     */
    public ExprProps(Request request, Properties defaults) {
  super(defaults);
  this.request = request;
  c = new Calculator(request.props);
    }

Examples of sunlabs.brazil.util.Calculator

Related Classes of sunlabs.brazil.util.Calculator