Assignment 5, due Sep 22

#!/bin/sh
# compare f1 f2
# script to compare and comment on differences between 2 files
echo comparing $1 with $2
if diff $1 $2; then
        echo true
else
        echo false
fi

If you store this script in a file called compare and make that file executable with chmod +x compare, you can run it with ./compare f1 f2 for any 2 files f1 and f2. (Try it with small files.) Note, in the script, $1 is a reference to the first command line argument, and $2 is a reference to the second. This is really bad language design, but it works, so we live with it.

a) Does the diff command return an idication of success or failure? If so, when does it indicate success and when does it indicate failure. The above script lets you test this empirically. (0.5 points)

b) In the notes for Lecture 8, the test file was threatening to get very long by the end. Suggest a script that could be used in the test script in order to allow each test to be coded on one line, assuming that there were existing files holding the input, the expected output, and the expected error messages for each test, stored in the testfiles directory. (0.5 points)

#!/bin/sh
# test command outfile errfile errmsg
# script to run command with given input and test outputs against expected
$1 > actualoutfile 2> actualerrfile
if ! diff $2 actualoutfile; then
        echo $4 ": standard output differs"
fi
if ! diff $3 actualerrfile; then
        echo $4 ": standard error differs"
fi
rm actualerrfile actualoutfile

#!/bin/sh
./test "java RoadNetwork" /dev/null test1error "test1 (missing infile)"
./test "java RoadNetwork x y" /dev/null test2error "test2 (too many args)"
./test "java RoadNetwork gribble" /dev/null test3error "test3 (can't open file)"
./test "java RoadNetwork /dev/null" /dev/null /dev/null "test3 (empty infile)"
./test "java RoadNetwork test4infile" test4outfile /dev/null "test4 (whatever)"

A problem: What output would you expect from your solution to MP2 when given this input? (1.0 points)

gate A and 1.0
gate B or 0.5
gate C neg 0.5
wire A out B in1 0.1
wire B out A in1 0.3
wire A out C in 0.1
wire C out B in2 0.1

inters.add( new Intersection( sc ) );

What we want, with either solution, is to not-only not create a new intersection, but not add anything to the list inters.

a) Rewrite this line so that it handles the Intersection.ConstructorFailure exception thrown by the constructor. (0.5 points)

try {
    inters.add( new Intersection( sc ) );
} catch (Intersection.ConstructorFailure e) {
}

b) Rewrite this line so that it handles a return value of null from a call to a factory method that replaces new Intersection(). (0.5 points)

Intersection i = Intersection.Factory( sc );
if (i != null) {
    inters.add( i );
}