Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
Using Example 26−8 as an inspiration, write a script that emulates a 64−bit shift register as an array.
Implement functions to load the register, shift left, and shift right. Finally, write a function that
interprets the register contents as eight 8−bit ASCII characters.
Determinant
Solve a 4 x 4 determinant.
Hidden Words
Write a "word−find" puzzle generator, a script that hides 10 input words in a 10 x 10 matrix of
random letters. The words may be hidden across, down, or diagonally.
Anagramming
Anagram 4−letter input. For example, the anagrams of word are: do or rod row word. You may use
/usr/share/dict/linux.words as the reference list.
Fog Index
The "fog index" of a passage of text estimates its reading difficulty, as a number corresponding
roughly to a school grade level. For example, a passage with a fog index of 12 should be
comprehensible to anyone with 12 years of schooling.
The Gunning version of the fog index uses the following algorithm.
1. Choose a section of the text at least 100 words in length.
2. Count the number of sentences (a portion of a sentence truncated by the boundary of the text
section counts as one).
3. Find the average number of words per sentence.
AVE_WDS_SEN = TOTAL_WORDS / SENTENCES
4. Count the number of "difficult" words in the segment −− those containing at least 3 syllables.
Divide this quantity by total words to get the proportion of difficult words.
PRO_DIFF_WORDS = LONG_WORDS / TOTAL_WORDS
5. The Gunning fog index is the sum of the above two quantities, multiplied by 0.4, then
rounded to the nearest integer.
G_FOG_INDEX = int ( 0.4 * ( AVE_WDS_SEN + PRO_DIFF_WORDS ) )
Step 4 is by far the most difficult portion of the exercise. There exist various algorithms for estimating
the syllable count of a word. A rule−of−thumb formula might consider the number of letters in a word
and the vowel−consonant mix.
A strict interpretation of the Gunning Fog index does not count compound words and proper nouns as
"difficult" words, but this would enormously complicate the script.
Calculating PI using Buffon's Needle
The Eighteenth Century French mathematician de Buffon came up with a novel experiment.
Repeatedly drop a needle of length "n" onto a wooden floor composed of long and narrow parallel
boards. The cracks separating the equal−width floorboards are a fixed distance "d" apart. Keep track
of the total drops and the number of times the needle intersects a crack on the floor. The ratio of these
two quantities turns out to be a fractional multiple of PI.
In the spirit of Example 12−35, write a script that runs a Monte Carlo simulation of Buffon's Needle.
To simplify matters, set the needle length equal to the distance between the cracks, n = d.
Hint: there are actually two critical variables: the distance from the center of the needle to the nearest
crack to it, and the angle of the needle to that crack. You may use bc to handle the calculations.
Playfair Cipher
Appendix I. Exercises 437