Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
filter ()
{
# Filter out negative array indices.
echo −n " " # Provides the tilt.
if [[ "$1" −ge 0 && "$1" −lt "$Rows" && "$2" −ge 0 && "$2" −lt "$Columns" ]]
then
let "index = $1 * $Rows + $2"
# Now, print it rotated.
echo −n " ${alpha[index]}" # alpha[$row][$column]
fi
}
rotate () # Rotate the array 45 degrees
{ # ("balance" it on its lower lefthand corner).
local row
local column
for (( row = Rows; row > −Rows; row−− )) # Step through the array backwards.
do
for (( column = 0; column < Columns; column++ ))
do
if [ "$row" −ge 0 ]
then
let "t1 = $column − $row"
let "t2 = $column"
else
let "t1 = $column"
let "t2 = $column + $row"
fi
filter $t1 $t2
done
# Filter out negative array indices.
echo; echo
done
# Array rotation inspired by examples (pp. 143−146) in
# "Advanced C Programming on the IBM PC", by Herbert Mayer
# (see bibliography).
}
#−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−#
load_alpha # Load the array.
print_alpha # Print it out.
rotate
# Rotate it 45 degrees counterclockwise.
#−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−#
# This is a rather contrived, not to mention kludgy simulation.
#
# Exercises:
Chapter 26. Arrays 308