JavaCC

1) Preliminaries. Obtain JavaCC and JJtree. JavaCC is a Java tool for building parsers

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and lexers, JJtree is an extension to it, provided as part of the JavaCC distribution. They

can be run from a command line, or in eclipse, or in netbeans.

Read at least the following pieces of documentation:

https://javacc.java.net/doc/javaccgrm.html

https://javacc.java.net/doc/JJTree.html

http://www.cs.may.ie/~jpower/Oberon/oberon.jj

The last one (Oberon-2 compiler) is used as a case study in lectures early next term.

2) Write the rules to allow JavaCC to build a lexical analyser for the various tokens of

this language. Do not have rules for strings, comments, octal hexadecimal or floating

point numbers: they are not part of this language.

3) Write the grammar rules to allow JavaCC to parse a complete error-free program in the

language. This involves removing extensive left recursion, performing left factoring on

rules relating to Test, and writing a valid JavaCC input specification.

4) Use JJtree to get a parse tree built.

5) Arrange for a ‘visitor’ to walk the tree and generate a list of 4-element vectors

representing instructions in 3-address code. The elements of the four-element vectors

should always be strings. The legal opcodes of these instructions are listed overleaf.

• The fields named Dest, Source1, Source2, Offset should be filled by names of

program variables or temporary variables created by your code generator. Such

temporary variables may be given names like t1, t2, t3 – since program variables

have no digits in their names there will be no danger of clashes.

• Note that the grammar specified gives a left-associative meaning to the “-”

operator.

• The “tag” argument to jump, jumpmore, jumpless, jumpequal, jumpnotequal and

label opcodes is another generated name like lbl1, lbl2 etc.

• Unused slots should always be filled with the empty string.

You are not asked to implement these instructions on any real or virtual machine. They

just provide the vocabulary of the language that your compiler is translating into.