Then, invoking Jacc on a grammar file from a terminal console is done by typing:
java ilog.language.syntax.Jacc <grammar file>Or, more conveniently by defining a command for invoking Jacc; e.g., in UNIX:
alias jacc java ilog.language.syntax.Jaccso that one need only type:
jacc <grammar file>to invoke it. Options available to Jacc are described by specifying no arguments. Thus:
jacc Usage: jacc [options] grammar_file(s) Option (Default) Description ------ --------- ----------- -doc () generate only the grammar documentation -i () tolerate an incomplete grammar (no parser is generated) -n () do not generate the parser -o (System.out) redirect the log to the specified file -e (System.err) redirect errors to the specified file -p (Parser) parser name (default: grammar="Foo.grm" => parser="FooParser.java") -rrp () resolve R/R conflicts based on precedence (dangerous!) -s (\) file separator character -m (1000) max number of instructions in parser initialization method -trail (100) max size of trail history (for dynamic parsing) -v (1) information verbosity (number between 0 and 4) -amb () allow ambiguous actions (for dynamic parsing) -choices (10) max size of choice history (for dynamic parsing)
A Jacc grammar for such a calculator is specified in the file Calculator.grm. To generate the parser corresponding to this grammar, one simply runs Jacc as indicated above on the grammar file. In our case:
% jacc Calculator *** Reading grammar in file Calculator.grm ... *** Starting grammar analysis ... *** Grammar analysis completed in 70 ms. *** Building parsing tables ... *** Writing parser file CalculatorParser.java *** Parser generation completed in 90 ms. *** Total processing time: 240 ms.This generates a parser for the specified grammar as a java program called CalculatorParser.java.
In order to have a complete system, we need a tokenizer and a driver.
Our calculator grammar uses a tokenizer class called CalculatorTokenizer. A possible implementation for it is shown in the file CalculatorTokenizer.java.
A simple driver for the complete calculator is shown in the file CalculatorMain.java.
Then, all one must do is compile the three files (parser, tokenizer, and driver) using javac, and the calculator is ready by executing its driver. To wit:
% java CalculatorMain *** Welcome to the number calculator! *** Version of Sun Dec 19 18:27:13 PST 2004 > 1+2; expression 'NUMBER'(1.0) '+' 'NUMBER'(2.0) 3.0 > a+1; *** Undefined identifier: a expression 'IDENTIFIER'(a) '+' 'NUMBER'(1.0) > a = 3.14159; definition 'IDENTIFIER'(a) '=' 'NUMBER'(3.14159) *** Defined a (3.14159) > b = 2*a+(a-1.234); definition 'IDENTIFIER'(b) '=' expression 'NUMBER'(2.0) '*' 'IDENTIFIER'(a) '+' '(' 'IDENTIFIER'(a) '-' 'NUMBER'(1.234) ')' *** Defined b (8.19077) > a-b+2/b; expression 'IDENTIFIER'(a) '-' 'IDENTIFIER'(b) '+' 'NUMBER'(2.0) '/' 'IDENTIFIER'(b) -4.805002712638739 > 1 ++ 2; *** Syntax Error: unexpected '+' - see stdin (line 6, column 4) > exit; *** Bye bye!... %Another similar example illustrating Jacc's handling of dynamic operators is described here. All concomitant files for it along with those done for the Calculator examples are also provided to let you run the example.