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Description
html markup
shown to student

Complete the program below by defining five strings, each containing a regular
expression to match one of the five languages indicated in the comments.
The first one is filled in for you as an example.
You may assume that we will only test your program on strings containing
the letters <tt>E</tt>, <tt>G</tt>, <tt>R</tt> and <tt>X</tt>.
Epilogue
html markup
shown when solved

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Public permissions remove
Remarks
Comments, history, license, etc.

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Engine
Choices
json list of string, bool pairs
e.g. [["good", true], ["bad", false]]

Correct answer
Template / Reference solution

public class RegularExercise {

// regular expression for: all strings that start with G or R
public static String startsWithGorR = "(G|R).*";

// regular expression for: all strings that contain a substring "EX"
public static String containsEX = \[".*EX.*"]\;

// regular expression for: all strings that do not contain an E
public static String noE = \["(R|G|X)*"]\;

// regular expression for: all strings in which every X is followed by a G
public static String everyXfollowedByG = \["(XG|G|R|E)*"]\;

// regular expression for: all strings that do not end with X
public static String doesNotEndWithX = \["(.*(G|R|E))|"]\;

public static void main(String[] args) {
StdOut.printf("%24s%12s%6s%18s%16s\n", "startsWithGorR", "containsEX",
"noE", "everyXfollowedByG", "doesNotEndWithX");
for (String a : args) {
StdOut.printf("%8s%16s%12s%6s%18s%16s\n", a,
a.matches(startsWithGorR),
a.matches(containsEX),
a.matches(noE),
a.matches(everyXfollowedByG),
a.matches(doesNotEndWithX));
}
}

}

Template / Reference solution

Java test suite
See manual

testMain("REGEX", "GREE", "XRXG", "XX");
test("main", (Object)new String[]{"", "R", "G", "E", "X"});
String[] letters = {"R","G","E","X"};
defaultOptions.quietOnPass = true;
for (String a : letters) for (String b : letters)
test("main", (Object)new String[]{a+b});
for (String a : letters) for (String b : letters)
for (String c : letters)
test("main", (Object)new String[]{a+b+c});
for (String a : letters) for (String b : letters)
for (String c : letters)
for (String d : letters)
test("main", (Object)new String[]{a+b+c+d});
for (String a : letters) for (String b : letters)
for (String c : letters)
for (String d : letters)
for (String e : letters)
test("main", (Object)new String[]{a+b+c+d+e});

C++ test suite
json list of stdin/args tests
e.g. [{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]
to just run once with no input use [{}]

C++ test suite
See manual

Forbidden substrings
json list of strings
e.g. ["for","while"]

remove
Solution visibility remove
Java imports
json list of importables
e.g. ["java.util.*"]

remove
Override Java classname
else defaults to
websheet name
remove
Dependent on other websheets?
json list of websheet names in this folder
e.g. ["DataStructure"]

remove
Is example?
i.e., just a demo
remove
Add compiler flag(s)
json list of flags
e.g. ["-Wno-unused-variable"]

remove
Remove default compiler flag(s)
json list of flags
see default_cppflags
e.g. ["-Wno-write-strings"]

remove

Property	Value
Description html markup shown to student	Complete the program below by defining five strings, each containing a regular expression to match one of the five languages indicated in the comments. The first one is filled in for you as an example. You may assume that we will only test your program on strings containing the letters <tt>E</tt>, <tt>G</tt>, <tt>R</tt> and <tt>X</tt>.
Epilogue html markup shown when solved	remove
Public permissions	remove
Remarks Comments, history, license, etc.	remove
Engine
Choices json list of string, bool pairs e.g. `[["good", true], ["bad", false]]`
Correct answer
Template / Reference solution	public class RegularExercise { // regular expression for: all strings that start with G or R public static String startsWithGorR = "(G\|R)."; // regular expression for: all strings that contain a substring "EX" public static String containsEX = \[".EX."]\; // regular expression for: all strings that do not contain an E public static String noE = \["(R\|G\|X)"]\; // regular expression for: all strings in which every X is followed by a G public static String everyXfollowedByG = \["(XG\|G\|R\|E)"]\; // regular expression for: all strings that do not end with X public static String doesNotEndWithX = \["(.(G\|R\|E))\|"]\; public static void main(String[] args) { StdOut.printf("%24s%12s%6s%18s%16s\n", "startsWithGorR", "containsEX", "noE", "everyXfollowedByG", "doesNotEndWithX"); for (String a : args) { StdOut.printf("%8s%16s%12s%6s%18s%16s\n", a, a.matches(startsWithGorR), a.matches(containsEX), a.matches(noE), a.matches(everyXfollowedByG), a.matches(doesNotEndWithX)); } } }
Template / Reference solution
Java test suite See manual	testMain("REGEX", "GREE", "XRXG", "XX"); test("main", (Object)new String[]{"", "R", "G", "E", "X"}); String[] letters = {"R","G","E","X"}; defaultOptions.quietOnPass = true; for (String a : letters) for (String b : letters) test("main", (Object)new String[]{a+b}); for (String a : letters) for (String b : letters) for (String c : letters) test("main", (Object)new String[]{a+b+c}); for (String a : letters) for (String b : letters) for (String c : letters) for (String d : letters) test("main", (Object)new String[]{a+b+c+d}); for (String a : letters) for (String b : letters) for (String c : letters) for (String d : letters) for (String e : letters) test("main", (Object)new String[]{a+b+c+d+e});
C++ test suite json list of stdin/args tests e.g. `[{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]` to just run once with no input use `[{}]`
C++ test suite See manual
Forbidden substrings json list of strings e.g. `["for","while"]`	remove
Solution visibility	remove
Java imports json list of importables e.g. `["java.util.*"]`	remove
Override Java classname else defaults to websheet name	remove
Dependent on other websheets? json list of websheet names in this folder e.g. `["DataStructure"]`	remove
Is example? i.e., just a demo	remove
Add compiler flag(s) json list of flags e.g. `["-Wno-unused-variable"]`	remove
Remove default compiler flag(s) json list of flags see default_cppflags e.g. `["-Wno-write-strings"]`	remove

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