Homework 01 (Due: Friday, March 5, 2021, 11 : 59 : 00PM) 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 Gravity Maze. 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: Maze and Moves . Each section is enclosed by start and end tags (begin{section} and end{section}, respectively). The value of the section is set by the :: assignment operator.
• Movesisantilde-separated(~)listofmovevaluesthatappearbetweenbegin{moves}andend{moves}. Valid moves are c (Clockwise rotation), cc (Counterclockwise rotation), and 180 (180 degree rota- tion).
• Maze is a two-dimensional array of space-separated entries that uses alphanumeric symbols to encode the state of the maze. Rows will be ended with a \ and the Maze will be begun with a begin{maze} and ended with a end{maze}.
• You may assume that tabs will not appear in the file.
An example of a properly formatted file is shown in Figure 1.
begin{ section } t i t l e {Moves} : : begin{moves} cc̃ 180̃ 180̃ c̃ 180̃ begin{ section } t i t l e {Maze} : : begin{maze}
x x x x x x x x x x x x x x\ x − − − − − − − − − − − − x\ x − − x − − − − − − x − x x\ x − − − − − − − x − − − − x\ x − − − − − − − − 2 − − − x\ x − − − − − − − − − − − − x\ x − g 1 − − − x − − − − − x\ x − − − − x − − − x − − − x\ xxxxxxxxxxxxxx
cc̃
c̃
c̃
cc̃ 180̃
cend{moves}
end{ section }
end{maze} end{section}
Figure 1: A properly formatted Gravity Game (G) 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 Gravity Game 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.
1
The purpose of the scanner is to extract tokens from the input and pass those along to the parser. For the Gravity Game encoding, the types of tokens that you will need to consider are given in Table 1.
1.2.1 Invalid Encodings
Type Section Beginning Section Ending Section Title Assign Value Move Symbol Maze Symbol Numerical Symbol Row Ending Maze Beginning Maze Ending List Beginning List Ending White Space (to be ignored)
Form
begin{section}
end{section}
title{Moves} and title{Maze}
::
c, cc, or l80
-, g, x, or one (1) or more numerical symbols 0,1,2,3,4,5,6,7,8,9
\
begin{maze}
end{maze}
begin{moves}
end{moves}
spaces, tabs, newlines
Table 1: Tokens to Consider
ForinvalidMazeGameencodings,theoutputThe unrecognizable token T appears in line L.should display. T would be the symbol read and 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 Gravity Game 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 /Maze or Maze /Moves order.
• There must be more than five (5) rows in a valid Maze .
• There must be more than five (5) columns in a valid Maze .
You may assume that each row has the same number of columns, and each column has the same number of rows.
• The first row, last row, first column, and last column of the Maze must contain only x symbols.
• There must be more than five (5) moves in the Moves section. The semantics of a properly formatted Maze Game encoding are:
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1. Between one (1) and four (4) (inclusive) players must appear in the Maze .
2. The Maze must contain exactly one (1) g symbol.
3. The number of x symbols in the Maze must not exceed 60% of all symbols in the Maze .
4. c, cc, and 180 must each appear at least once in the Moves .
5. Extra Credit (10 points or Honors contract): The goal must not be adjacent to an x symbol (considering only the up, down, left, and right directions).
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
Open Section: begin{section} Section Title: title{Moves} Designation: ::
Open Moves: begin{moves} Move: cc
…
Move: c
Close Moves: end{moves} Close Section: end{section} Open Section: begin{section} Section Title: title{Maze} Designation: ::
Open Maze: begin{maze} Location: x
…
Location: x
Close Row: \
Location: x
…
Location: x
Close Maze: end{maze}
Close Section: end{section} Close 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: This game has p players. where p is the
number of players in the Maze . For the file in Figure 1, the output would be This game has 2 players.. 2.1.1 Invalid Syntax & Semantics in Parsing
For invalid Maze Game encodings in Part 2, a message describing the error should be displayed. For a syntax error (violation of the syntax rules), the output
Something unexpected happened on Line L. should be displayed, where L is the line number where parsing stopped. For that error, the parser should stop processing the file. For a semantic rule violation, the output
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The semantic rule R was violated. should be displayed, where R is the number of the rule (from List 1.3) that was violated, but parsing should continue.
Syntax errors in Part 2 should be reported in the syntaxError method of csce322hw01pt02error.java.
3 Naming Conventions
The ANTLR file for the first part of the assignment should be named csce322hw01pt01.g4. The ANTLR file for the second part of the assignment should be named csce322hw01pt02.g4. Both grammars should contain a start rule named gravityGame. The Java file for the second part of the assignment should be named csce322hw01pt02error.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, output will be sorted (and duplicate lines removed), so diff will also be used to compared submission and solution output.
5 Point Allocation
Component
Points
Part 1
Test Cases Compilation Total
2%×10 15% 35%
Part 2
Test Cases Compilation Total
3%×15 20% 65%
Total
100%
6 External Resources
ANTLR
Getting Started with ANTLR v4 ANTLR 4 Documentation
Overview (ANTLR 4 Runtime 4.9 API)
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7 Commands of Interest
alias antlr4=’java -jar /path/to/antlr-4.9.1-complete.jar’ alias grun=’java org.antlr.v4.gui.TestRig ‘
export CLASSPATH=”/path/to/antlr -4.9.1-complete.jar:$CLASSPATH” antlr4 /path/to/csce322hw01pt0#.g4
javac -d /path/for/.classfiles /path/to/csce322hw01pt0#*.java
java /path/of/.classfiles csce322hw01pt02driver /path/to/inputfile grun csce322hw01pt0# gravityGame -gui
grun csce322hw01pt0# gravityGame -gui /path/to/inputfile
grun csce322hw01pt0# gravityGame
grun csce322hw01pt0# gravityGame /path/to/inputfile
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