Built-ins

Batteries included!

Kal does not come with a separate standard library. Rather, everything is intrinsic to the interpreter. This chapter covers general intrinsics.

Kal exposes a global

ARGS

list variable that contains all the command line arguments. Command line arguments are additional pieces of information passed to the interpreter while passing the program.

stdout ARGS "\n".

args.kal

$ kal args.kal sun earth moon

Arguments can be extracted from

ARGS

as you would from a normal list.

stdout ARGS[3] "\n".

args.kal

$ kal args.kal sun earth moon

You can make Kal programs end early using the

exit

statement.

exit 100.
stdout "Won't run!".

exit.kal

$ kal exitCode.kal
$ echo $?

Text can be colorized using the

style

statement. It accepts color, mode or a combination of both.

style "red" "bold".
stdout "Text Red!\n".

color.kal

Valid colors and modes are:

Colors	Modes
black	bold
red	italic
green	underline
yellow	blink
blue	bg
magenta	strike
cyan	reset
white

Use

"reset"

to go back to default.

style "reset".

reset.kal

Kal comes with statements for working with lists and dictionaries. Those are documented as follows.

Add a new element to a list using the

push

statement.

var data = [1, 2, 3].
stdout "Before: " data "\n".

push data 4.
stdout "After: " data "\n".

push.kal

By default Kal will push an element to the end of the list. Optionally provide the index where you want to push the element to as the third argument.

var data = [1, 2, 3].
stdout "Before: " data "\n".

push data 4 1.
stdout "After: " data "\n".

pushIndex.kal

Fetch the first element of a list using the

first

statement.

var data = ["x", "y", "z"].
first data -> f.
stdout "First: " f "\n".

first.kal

Fetch the last element of a list using the

last

statement.

var data = ["x", "y", "z"].
last data -> l.
stdout "Last: " l "\n".

last.kal

Remove the last element of the list using the

pop

statement.

var data = [1, 2, 3].
stdout "Before: " data "\n".

pop data.
stdout "After: " data "\n".

pop.kal

Remove the first element of the list using the

popFirst

statement.

var data = [1, 2, 3].
stdout "Before: " data "\n".

popFirst data.
stdout "After: " data "\n".

popFirst.kal

Reverse a list using the reverse statement.

var data = [1, 2, 3].
stdout "Before: " data "\n".

reverse data.
stdout "After: " data "\n".

reverse.kal

Concatenate lists using the

extend

statement.

var listX = [1, 2, 3],
    listY = [4, 5, 6].

extend listX listY -> listZ.
stdout listZ "\n".

extend.kal

Flatten nested lists into a linear list using the

flat

statement.

var data = [
    [1, 2, 3],
    [4, 5, 6]
].

flat data -> line.
stdout line "\n".

flat.kal

There could be many levels of list nesting, simple invocation of the

flat

statement only removed the top level Pass in the number of levels you want to resolve in case of deeply nested lists.

var data = [
    [1, [2, 3]],
    [4, [5, 6]]
].

flat data -> line.
stdout "First Level: " line "\n".

;; resolve of 2 levels
flat data 2 -> secondLine.
stdout "Second Level: " secondLine "\n".

flatLevels.kal

For a dictionary, use the

keys

statement to obtain a list of all keys.

var planet = #(
    name -> "Earth",
    is -> "Planet"
).

keys planet -> dictKeys.
stdout "Keys = " dictKeys "\n"

keys.kal

Similarly, use the

values

statement to obtain a list of all values.

var planet = #(
    name -> "Earth",
    is -> "Planet"
).

values planet -> dictValues.
stdout "Values = " dictValues "\n".

values.kal

To obtain combined key-value pairs, use the

items

statement.

var planet = #(
    name -> "Earth",
    is -> "Planet"
).

items planet -> dictItems.
stdout "Items = " dictItems "\n".

items.kal

Check whether a key exists or not in a dictionary using the

exists

statement.

var planet = #(
    name -> "Earth",
    is -> "Planet"
).

exists planet "name" -> x.
exists planet "biomes" -> y

stdout "Name? " x "\n"
    "Biomes? " y "\n".

items.kal

Update an existing dictionary using the

update

statement.

update

takes in another dictionary and patches it over the original one. This adds or updates values in the original dictionary.

var planet = #(
    name -> "Earth",
    is -> "Planet"
).

var planetPatch = #(
    name -> "Home",
    biomes -> ["Forest", "Ocean"]
).

update planet planetPatch -> final.
stdout final "\n".

update.kal

Finally, use the

len

statement to get the length of a list, dictionary or a string. It returns the number of elements, the number of keys and the number of characters for these respective types.

var data = [1, 2, 3].
len data -> listLen.

var info = #(
    name -> "Earth",
    home -> "yes"
).
len info -> dictLen.

var day = "24 hours".
len day -> strLen.
stdout listLen "\n"
    dictLen "\n"
    strLen "\n".

len.kal

Throughout the examples we used lists and dictionaries as variables. However, you can also pass them to these statements as literals.

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