Add descriptions to each exercise

.template.lua

@@ -1,3 +1,5 @@
+-- Description
+--
 -- Solution --------------------------------------------------------------------
 function f()
 	-- Your implementation here

anagrams.lua

@@ -1,3 +1,7 @@
+-- Implement the is_anagram() function below, so that it returns true if
+-- the two passed strings are anagrams of each other.  Any non-
+-- alphabetical characters in the string should be ignored.
+--
 -- Solution --------------------------------------------------------------------
 function is_anagram(str1, str2)
 	-- Your implementation here

balanced_brackets.lua

@@ -1,3 +1,7 @@
+-- Implement is_balanced(), which should return true or false depending
+-- on whether the brackets in the input string are balanced,
+-- i.e. there is a closing bracket for each opening one.
+--
 -- Solution --------------------------------------------------------------------
 function is_balanced(input)
 	-- Your implementation here

fibonacci_numbers.lua

@@ -1,3 +1,5 @@
+-- Write a function to calculate the nth fibonacci number.
+--
 -- Solution --------------------------------------------------------------------
 function nth_fibonacci_number(n)
 	-- Your implementation here

greatest_common_divisor.lua

@@ -1,3 +1,7 @@
+-- The greatest common divisor (GCD) of two numbers X and Y is, as the
+-- name suggests, the largest number which evenly divides both X and
+-- Y.  Implement the function below to calculate this.
+--
 -- Solution --------------------------------------------------------------------
 function greatest_common_divisor(x, y)
 	-- Your implementation here

hamming_distance.lua

@@ -1,3 +1,8 @@
+-- The hamming distance is the number of positions in which two
+-- strings differ, and is used to measure how similar strings are.
+-- Implement the hamming_distance() function below to calculate this;
+-- you may assume that the strings are of equal length.
+--
 -- Solution --------------------------------------------------------------------
 function hamming_distance(str1, str2)
 	-- Your implementation here

hexadecimal.lua

@@ -1,3 +1,6 @@
+-- Write a function to return the hexadecimal representation (in a
+-- string) of a number.  Use lowercase a to f.
+--
 -- Solution --------------------------------------------------------------------
 function hexadecimal(x)
 	-- Your implementation here

leap_years.lua

@@ -1,3 +1,6 @@
+-- Implement is_leap_year() below, returning whether the given year is
+-- a leap year according to the Gregorian calendar.
+--
 -- Solution --------------------------------------------------------------------
 function is_leap_year(year)
 	-- Your implementation here

maximum.lua

@@ -1,3 +1,5 @@
+-- Implement a function to return the largest value in a list.
+--
 -- Solution --------------------------------------------------------------------
 function maximum(list)
 	-- Your implementation here

palindromes.lua

@@ -1,3 +1,7 @@
+-- Implement is_palindrome(), which should return whether the passed
+-- string is palindromic (i.e the same forwards as it is backwards).
+-- Ignore non-letters and case.
+--
 -- Solution --------------------------------------------------------------------
 function is_palindrome(str)
 	-- Your implementation here

prime_numbers.lua

@@ -1,3 +1,5 @@
+-- Write a function to determine whether a given number is prime.
+--
 -- Solution --------------------------------------------------------------------
 function is_prime(x)
 	-- Your implementation here

queen_threats.lua

@@ -1,3 +1,8 @@
+-- Implement the function is_queen_threat() below.  It should return
+-- true if the queen is threatening the pawn and false otherwise.  The
+-- coordinates are as given as file (A-H), rank (1-8) pairs such as B3
+-- and D7.
+--
 -- Solution --------------------------------------------------------------------
 function is_queen_threat(queen_position, pawn_position)
 	-- Your implementation here

resistor_colours.lua

@@ -1,3 +1,7 @@
+-- Write a function to determine the resistance (in ohms) of a given
+-- three-part resistor colour code.  The colour code is passed as a
+-- list of strings.
+--
 -- Solution --------------------------------------------------------------------
 function decode_resistance(colours)
 	-- Your implementation here