Added build files to turn the bible into a book

manuscript/chapter2.txt

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+# Arrays
+
+## Reverse an array
+
+Enabling `extdebug` allows access to the `BASH_ARGV` array which stores
+the current function’s arguments in reverse.
+
+**Example Function:**
+
+```sh
+reverse_array() {
+    # Usage: reverse_array "array"
+    shopt -s extdebug
+    f()(printf '%s\n' "${BASH_ARGV[@]}"); f "$@"
+    shopt -u extdebug
+}
+```
+
+**Example Usage:**
+
+```shell
+$ reverse_array 1 2 3 4 5
+5
+4
+3
+2
+1
+
+$ arr=(red blue green)
+$ reverse_array "${arr[@]}"
+green
+blue
+red
+```
+
+## Remove duplicate array elements
+
+Create a temporary associative array. When setting associative array
+values and a duplicate assignment occurs, bash overwrites the key. This
+allows us to effectively remove array duplicates.
+
+**CAVEAT:** Requires `bash` 4+
+
+**Example Function:**
+
+```sh
+remove_array_dups() {
+    # Usage: remove_array_dups "array"
+    declare -A tmp_array
+
+    for i in "$@"; do
+        [[ "$i" ]] && IFS=" " tmp_array["${i:- }"]=1
+    done
+
+    printf '%s\n' "${!tmp_array[@]}"
+}
+```
+
+**Example Usage:**
+
+```shell
+$ remove_array_dups 1 1 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5
+1
+2
+3
+4
+5
+
+$ arr=(red red green blue blue)
+$ remove_array_dups "${arr[@]}"
+red
+green
+blue
+```
+
+## Random array element
+
+**Example Function:**
+
+```sh
+random_array_element() {
+    # Usage: random_array_element "array"
+    local arr=("$@")
+    printf '%s\n' "${arr[RANDOM % $#]}"
+}
+```
+
+**Example Usage:**
+
+```shell
+$ array=(red green blue yellow brown)
+$ random_array_element "${array[@]}"
+yellow
+
+# You can also just pass multiple arguments.
+$ random_array_element 1 2 3 4 5 6 7
+3
+```
+
+## Cycle through an array
+
+Each time the `printf` is called, the next array element is printed. When
+the print hits the last array element it starts from the first element
+again.
+
+```sh
+arr=(a b c d)
+
+cycle() {
+    printf '%s ' "${arr[${i:=0}]}"
+    ((i=i>=${#arr[@]}-1?0:++i))
+}
+```
+
+
+## Toggle between two values
+
+This works the same as above, this is just a different use case.
+
+```sh
+arr=(true false)
+
+cycle() {
+    printf '%s ' "${arr[${i:=0}]}"
+    ((i=i>=${#arr[@]}-1?0:++i))
+}
+```
+
+<!-- CHAPTER END -->
+