code vs comment

ปกติเวลาเราเขียนโปรแกรม
source code คือเนื้อหาหลัก ส่วน comment คือเนื้อหารอง
,comment จะแทรกอยู่ใน source code โดยมี prefix พิเศษนำหน้า

haskell มันมี file format อยู่อันหนึ่งที่เรียกว่า "lhs"
ถ้าอยู่ใน format นี้ source code จะหลายเป็นเนื้อหารองแทน
(คือต้องมี prefix นำหน้า)

-------------------------------------------------------------------------------
                        Haskell code and test cases
                         for the non-monadic stages
-------------------------------------------------------------------------------

This file contains the Haskell code for the various non-monadic stages
in the derivation of a Gaussian Elimination program using the
methodology. The remaining programs are in other files in the same
directory.

It also contains 3 sets of test data. Typing "main" runs the programs
for each non-monadic stage on this data and prints the results.

It needs modules which provide finite sequences:

> import SeqFinSeq
> import ParFinSeq
> import Cyclic

-------------------------------------------------------------------------------
The following function runs the functions on the test data:

> main :: IO()
> main = do putStr "The test data is:\n"
>           putStr "1st set: \n"
>           putStr ("a = " ++ (show a_matrix) ++ "\n")
>           putStr ("b = " ++ (show b_vector) ++ "\n")
>           putStr "2nd set: \n"
>           putStr ("a = " ++ (show a2_matrix) ++ "\n")
>           putStr ("b = " ++ (show b2_vector) ++ "\n")
>           putStr "3rd set: \n"
>           putStr ("a = " ++ (show a3_matrix) ++ "\n")
>           putStr ("b = " ++ (show b3_vector) ++ "\n")


------------------------------
Test data (need a matrix A and a vector b)

> a_matrix :: Matrix Rational
> a_matrix = [[2,3],[1,-1]]
> b_vector :: Vector Rational
> b_vector = [25,10]