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Draft

Operations on Arrays

Initialization

declare -a array 
declare -a array=()

declare -A assoc
# there is no empty literal here

Also valid, but not necessary since declare is local:

local -a array
local -A assoc

Makes a global array:

array=()

Array Literals

Respects the normal rules of argv.

prefix=foo
myarray=(one two -{three,four}- {5..8} *.py "$prefix*.py" '$prefix*.py')

myarray=(
  $var ${var} "$var" 
  $(echo hi) "$(echo hi)"
  $(1 + 2 * 3)
)

Associative Array Literals

(['k']=v)

Unlike bash, ([0]=v) is still an associative array literal.

It's not an indexed array literal.  This matters when you take slices and
so forth?

"${a[@]}" is Evaluating (Splicing)

echo "${array[@]}"
echo "${assoc[@]}"

Not Allowed, unlike in bash!

$assoc  ${assoc}  "${assoc}"
${!assoc}  ${assoc//pattern/replace}  # etc.

Iteration

Note that since a for loop takes an array of words, evaluating/splicing works:

for i in "${a1[@]}" "${a2[@]}"; do
  echo $i
done

${#a[@]} is the Length

echo ${#array[@]}
echo ${#assoc[@]}

Coercion to String by Joining Elements

echo ${!array[@]}
echo ${!assoc[@]}

echo ${!array[*]}
echo ${!assoc[*]}

echo "${!array[*]}"
echo "${!assoc[*]}"

Look Up By Index / Key With a[]

matrix: a['x'] a["x"] a["$x"] a[$x] a[${x}] a[${x#a}]

a[x] -- allowed
A[x] -- NOT allowed?  It should be a string

(( 'a' )) -- parsed, but can't evaluate

# This is a string in both cases
a[0]
A[0]

undef[0]=1 automatically creates an INDEXED array undef=(1)

Assign / Append To Location Specified by Index / Key

a[expr]=    # int_coerce
A[expr]=    # no integer coercion

Just like you can append to strings:

s+='foo'

Append to elements of an array, which are strings:

a[x+1]+=x
a[x+1]+=$x

Slicing With ${a[@]:5:2}

${array[@]:1:3}

Note the presence of DISALLOWED VALUES.

# TODO: disallow this?  because no order
${assoc[@]:1:3}

NOTE: string slicing:

Append Array to Array

a=(1 2 3)
a+=(4 5 6)

Get All Indices With ${!a[@]}

echo ${!array[@]}
echo ${!assoc[@]}

Vectorized String Operations

echo ${array[@]//x/X}

echo ${assoc[@]//x/X}