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Homework 01 (Due: Friday, February 15, 2019, 11 : 59 : 00PM Central
Time)
CSCE 322
1 Instructions
In this assignment, you will be required to scan, parse, and check the semantics of a file that encodes the
state of a variation of Connect Four. The definition of a properly formatted input file is given in Section 1.1.
You will be submitting one .java file and two .g4 (ANTLR) files via web hand-in.
1.1 File Specification
• The file contains two (2) labeled sections: Moves and Game . Each section is enclosed by start and
end tags (/* and */, respectively).
• Moves is an underscore-separated (_) list of numbered columns that appear between { and } tokens.
Valid Moves are numerical symbols.
• Game contains a two-dimensional array of space-separated entries that uses numeric symbols (and
-) to encode the state of the game. Rows will be ended with a | and the Game will be begun with a
[ and ended with a ]. The two-dimensonal array contains numbers where that player (for example,
1 for Player 1) has played a piece and – for an empty space.
An example of a properly formatted file is shown in Figure 1.
moves /∗
{ 5 10 9 4 1 2 10 10 2 2 1 9 1 3 }
∗/
game /∗
[
− − − − − − − − − − |
− − − − − − − − − − |
− − − − − − − − − − |
− − − − − − − − − − |
− − − − − − − − − − |
− − − − − − − − − − |
− − − 2 − − − 1 − −
]
∗/
Figure 1: A properly formatted Connect Four (cnf) encoding
The assignment is made up of two parts: scanning the text of the input file and parsing the information
contained in the input file.
1.2 Scanning
Construct a combined grammar in a .g4 file that ANTLR can use to scan a supplied Connect Four
encoding. The logic in this file should be robust enough to identify tokens in the encoding and accurately
process any correctly formatted encoding. The rules in your .g4 file will be augmented with actions that
display information about the input file. An example of that output is specified in Section 2.
The purpose of the scanner is to extract tokens from the input and pass those along to the parser. For
the Connect Four encoding, the types of tokens that you will need to consider are given in Table 1.
1
Type Form
Section Beginning /*
Section Ending */
Section Title game and moves
Move Symbol One or more Numerical Symbols
Game Symbol – or One or more Numerical Symbols
Numerical Symbol 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9
Row Ending |
Game Beginning [
Game Ending ]
Moves Beginning {
Moves Ending }
White Space (to be ignored) spaces, tabs, newlines
Table 1: Tokens to Consider
1.2.1 Invalid Encodings
For invalid Connect Four encodings, the output SYNTAX PROBLEM ON LINE L should display. L would
be the line of input where the symbol was read. Your scanner should stop scanning the file after an
unrecognized token is found.
1.3 Parsing
Construct a combined grammar in a .g4 file that ANTLR can use to parse a supplied Connect Four
encoding. In addition to the rules for scanning, there are several parsing rules:
• Each section appears once and only once. The sections may appear in either Moves /Game or
Game /Moves order.
• There must be at least four (4) rows in a valid Game .
• There must be at least four (4) columns in a valid Game .
You may assume that each row has the same number of columns, and each column has
the same number of rows.
• There must be at least two (2) locations in the Moves section.
The semantics of a properly formatted Connect Four encoding are:
1. The Game must have at least 2 players
2. The Game must have between 6 and 10 (both inclusive) rows
3. The Game must have between 6 and 10 (both inclusive) columns
4. Extra Credit (10 points or Honors contract): Every move in the Moves section must be valid
(between 1 and the number of columns in the Game )
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2 Output
2.1 Scanner
Your .g4 file should produce output for both correctly formatted files and incorrectly formatted files. For
the correctly formatted file in Figure 1, the output would have the form of the output presented in Figure 2
Moves Section
Beginning of Section
Beginning of List
Number : 5
Number : 10

Number : 1
Number : 3
End of List
End of Section
Game Section
Beginning of Section
Start of Game
Space : Empty
Space : Empty

Space : Empty
End of Row
Space : Empty

Space : Empty
End of Row
Space : Empty

Space : Empty
End of Row
Space : Empty
Space : Empty
Space : Empty
Number : 2
Space : Empty
Space : Empty
Space : Empty
Number : 1
Space : Empty
Space : Empty
End of Game
End of Section
End of File
Figure 2: Truncated Output of Scanner for File in Figure 1
For a correctly formatted file in Part 2, the output would be: p pieces have been played where p
is the number of pieces in the Game . For the file in Figure 1, the output would be
2 pieces have been played.
2.1.1 Invalid Syntax & Semantics in Parsing
For invalid encodings in Part 2, the message SYNTAX PROBLEM ON LINE L should be displayed where L is
the line number where the error occurred. For a semantic rule violation, the output
SEMANTIC PROBLEM P should be displayed, where P is the number of the rule (from List 1.3) that was
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violated, but parsing should continue.
Syntax errors in Part 2 should be reported in the syntaxError method of
csce322assignment01partt02error.java.
3 Naming Conventions
The ANTLR file for the first part of the assignment should be named csce322assignment01part01.g4.
The ANTLR file for the second part of the assignment should be named csce322assignment01part02.g4.
Both grammars should contain a start rule named connectFour. The Java file for the second part of the
assignment should be named csce322assignment01part02error.java.
4 webgrader
The webgrader is available for this assignment. You can test your submitted files before the deadline
by submitting them on webhandin and going to http://cse.unl.edu/˜cse322/grade, choosing the correct
assignment and entering your cse.unl.edu credentials
The script should take approximately 2 minutes to run and produce a PDF.
4.1 The Use of diff
Because Part 1 of this assignment only depends on the symbols in the file, the order in which they are
displayed should not be submission dependent. Therefore, diff will be used to compare the output of a
particular submission against the output of the solution implementation. In Part 2, the output is sorted
and the unique lines extracted, so the order and number of times a semantic error is reported will not
affect the diff.
5 Point Allocation
Component Points
Part 1 35
Part 2 65
Total 100
6 External Resources
ANTLR
Getting Started with ANTLR v4
ANTLR 4 Documentation
Overview (ANTLR 4 Runtime 4.7.2 API)
7 Commands of Interest
alias antlr4 =’ java – jar / path / to / antlr -4.7.2 – complete . jar ‘
alias grun =’ java org . antlr . v4 . gui . TestRig ‘
export CLASSPATH =”/ path / to / antlr -4.7.2 – complete . jar : $CLASSPATH ”
antlr4 / path / to / csce322assignment01part0 #. g4
javac -d / path / for /. classfiles / path / to / csce322assignment01part0 #*. java
java / path / of /. classfiles csce322assignment01part02driver / path / to / inputfile
grun csce322assignment01part0 # connectFour – gui
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grun csce322assignment01part0 # connectFour – gui / path / to / inputfile
grun csce322assignment01part0 # connectFour
grun csce322assignment01part0 # connectFour / path / to / inputfile
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In this assignment, you will be required to scan, parse, and check the semantics of a file that encodes the state of a variation of Connect Four.
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