Data-Processing: Grade Book Example

123456:Washington,George:SR
246802:Lincoln,Abraham "Abe":SO
357913:Jefferson,Thomas:JR
212121:Roosevelt,Theodore "Teddy":SO

123456 1 98
212121 1 86
246802 1 89
357913 1 90
123456 2 96
212121 2 88
357913 2 92
123456 3 97
212121 3 96
246802 3 95
357913 3 94

Stu-ID Name... 1 2 3 Totals:

357913 Jefferson,Thomas 90 92 94 276
246802 Lincoln,Abraham "Abe" 89 95 184
212121 Roosevelt,Theodore "Teddy" 86 88 96 270
123456 Washington,George 98 96 97 291

Totals: 363 276 382

#!/usr/local/bin/perl
# Gradebook - demonstrates I/O, associative
# arrays, sorting, and report formatting.
# This accommodates any number of exams and students
# and missing data. Input files are:
$stufile='stufile';
$scorefile='scorefile';

# If file opens successfully, this evaluates as "true", and Perl
# does not evaluate rest of the "or" "||"
open (NAMES,"<$stufile")
|| die "Can't open $stufile $!";
open (SCORES,"<$scorefile")
|| die "Can't open $scorefile $!";

# Build an associative array of student info
# keyed by student number

while (<NAMES>) {
($stuid,$name,$year) = split(':',$_);
$name{$stuid}=$name;
if (length($name)>$maxnamelength) {
$maxnamelength=length($name);
}
}
close NAMES;

# Build a table from the test scores:

while (<SCORES>) {
($stuid,$examno,$score) = split;
$score{$stuid,$examno} = $score;
if ($examno > $maxexamno) {
$maxexamno = $examno;
}
}
close SCORES;

# Print the report from accumulated data!

printf "%6s %-${maxnamelength}s ",
'Stu-ID','Name...';
foreach $examno (1..$maxexamno) {
printf "%4d",$examno;
}
printf "%10s\n\n",'Totals:';

# Subroutine "byname" is used to sort the %name array.
# The "sort" function gives variables $a and $b to
# subroutines it calls.
# "x cmp y" function returns -1 if x<y, 0 if x=y,
# +1 if x>y. See the Perl documentation for details.

sub byname { $name{$a} cmp $name{$b} }

# Order student IDs so the names appear alphabetically:
foreach $stuid ( sort byname keys(%name) ) {
# Print scores for a student, and a total:
printf "%6d %-${maxnamelength}s ",
$stuid,$name{$stuid};
$total = 0;
foreach $examno (1..$maxexamno) {
printf "%4s",$score{$stuid,$examno};
$total += $score{$stuid,$examno};
$examtot{$examno} += $score{$stuid,$examno};
}
printf "%10d\n",$total;
}

printf "\n%6s %${maxnamelength}s ",'',"Totals: ";
foreach $examno (1..$maxexamno) {
printf "%4d",$examtot{$examno};
}
print "\n";
exit(0);