Data munging task from the Perl 6 advent calendar

grades.tcl

#!/usr/bin/env tclsh

package require sqlite3
package require fileutil

sqlite3 db :memory:
db eval {CREATE TABLE grades(name TEXT PRIMARY KEY, grade TEXT)}

foreach {name grade} [::fileutil::cat grades.txt] {
    if {![regexp {[A-F][+-]?} $grade]} {
        puts "Can't parse pair '$name $grade'"
        exit 1
    }
    db eval {INSERT INTO grades VALUES ($name, $grade)}
}

puts "Zsófia's grade: [db eval {SELECT grade FROM grades WHERE name='Zsófia'}]"

puts "List of students with a failing grade:"
puts "  [join [
    db eval {SELECT name FROM grades WHERE grade >= 'E' ORDER BY grade}
] {, }]"

set grades [db eval {
    SELECT DISTINCT trim(grade, '+-') FROM grades ORDER BY grade
}]
puts "Distribution of grades by letter:"
foreach grade $grades {
    puts -nonewline "  $grade: "
    set count [db eval {
        SELECT count(name) FROM grades WHERE trim(grade, '+-')=$grade
    }]
    puts -nonewline "$count student"
    if {$count > 1} { puts -nonewline s }
    puts {}
}

grades.txt

Peter	B
Celine	A-
Zsófia	B+
João	F
Maryam	B+
秀英	B-
Finn	D+
Aarav	A
Emma	F
Omar	B

output.txt

Zsófia's grade: B+
List of students with a failing grade:
  João, Emma
Distribution of grades by letter:
  A: 2 students
  B: 5 students
  D: 1 student
  F: 2 students

An outdated version of the code for https://dbohdan.com/wiki/data-munging.