Data Types ​

The following page describes the most important data types. Some types may not be described here.

Boolean ​

Booleans are expressed using the true and false keywords.

Conversions ​

Dictionary ​

Dictionaries represent key-value pairs with unique keys. This can be expressed by putting comma-separated key-value pairs inside braces, such as { key1: value1, key2: value2 }. Indexing is done with square brackets, eg. dict["key1"] or with the indexing operator, eg. dict->key1.

let dict = {
    "key1": "x",
    "key2": "y",
}
assert(dict["key1"] == "x")
assert(dict->key2 == "y")

let dict = {
    "key1": "x",
    "key2": "y",
}
assert(dict["key1"] == "x")
assert(dict->key2 == "y")

Conversions ​

Iteration ​

When a dictionary is iterated over, a tuple containing the key and the value is given.

for key, value in dict: echo("${key}: ${value}")

for key, value in dict: echo("${key}: ${value}")

Error ​

The error type is used to represent errors and contains a string with an error message. An error message can be created using the error function, and the message can be retrieved by calling the message function.

let err = error("some error message")
if err | isType(Error): assert(message(err) == "some error message")

let err = error("some error message")
if err | isType(Error): assert(message(err) == "some error message")

Conversions ​

Float ​

Floats represent 64-bit floating point numbers and are created from number literals that contain decimals.

Conversions ​

Integer ​

Integers represent 64-bit integer numbers and are created from number literals that do not contain decimals.

Conversions ​

List ​

A list is a mutable dynamic data structure that can contain several values. Values are separated by commas. Indexing is done with square brackets and starts at zero. It is possible to index a list based on a range value in order to get a sub-list.

let items = [1, 2, 3]
assert(items[0] == 1)
items | add(4)
items | remove(0)

for item in items: echo(item)

let items = [1, 2, 3]
assert(items[0] == 1)
items | add(4)
items | remove(0)

for item in items: echo(item)

Conversions ​

Nil ​

Nil values are represented by the nil keyword.

Conversions ​

Generator ​

A Generator represents lazily evaluated values. A Generator can be collected with the function iter::collect.

# prints "hello" indefinitely
# `iter::repeat` returns a generator
for x in iter::repeat("hello") {
    println(x)
}

# prints "hello" indefinitely
# `iter::repeat` returns a generator
for x in iter::repeat("hello") {
    println(x)
}

Conversions ​

Pipe ​

Pipe objects are returned by program invocations and let you iterate over the program's stdout/stderr (depending on if it was piped with |, |err or |all). When iterating over a Pipe, the output stream is consumed line by line, but also buffered inside the object itself in order to make it possible to access these values later. Pipes can be implicitly converted to strings.

::: into Normally, the content of a Pipe is kept in memory for as long as the Pipe exists. However, when a Pipe object is piped to a program invocation or an std call that consumes it immediately, data is not stored in the Pipe, since it is consumed immediately anyway.

This means that you do not have to worry about excessive memory usage in these cases. :::

# `cat` returns a Pipe
# `map` will iterate over the file content line by line 
cat file.txt | map => x: x + "!"

# gets the 6th line
cat("file.txt")[5] | println

# converts the Pipe into a string and then applies str::upper
cat file.txt | str::upper

# `cat` returns a Pipe
# `map` will iterate over the file content line by line 
cat file.txt | map => x: x + "!"

# gets the 6th line
cat("file.txt")[5] | println

# converts the Pipe into a string and then applies str::upper
cat file.txt | str::upper

Conversions ​

Iteration ​

Iterating over a Pipe yields the individual lines.

Range ​

A range expresses a numerical range between two values. The syntax for a regular range is x..y where x and yare any type of expressions. Both expressions are expected to be integer values. When the first value is excluded, eg. ..y, the range will start at 0. When the last value is excluded, eg. x.., the range will not have a defined end.

Regular ranges are exclusive, meaning they don't include the value of the second expression. Iterating over the range 0..10 only yields the numbers 0 to 9. To instead make a range inclusive, an equal sign is added after the dots, eg. 0..=10.

for i in 0..10: echo(i)
let list = [1, 2, 3, 4, 5]
echo(list[1..3])

for i in 0..10: echo(i)
let list = [1, 2, 3, 4, 5]
echo(list[1..3])

Conversions ​

Iteration ​

Iterating over a range yields every number in the range.

Regex ​

A compiled regex pattern can be built by putting a pattern inside two slashes. Functions from the regex module and others can then be used together with the regex value.

# the regex functions take a Regex object, but
# will also implicitly convert strings to Regex
"abcdabdeghab" | re::findAll '[abc]'

# if you're going to use a pattern several times,
# it's better to create the Regex object immediately
let pattern = into::regex('[abc]')
"abcdabdeghab" | re::findAll(pattern)

# the regex functions take a Regex object, but
# will also implicitly convert strings to Regex
"abcdabdeghab" | re::findAll '[abc]'

# if you're going to use a pattern several times,
# it's better to create the Regex object immediately
let pattern = into::regex('[abc]')
"abcdabdeghab" | re::findAll(pattern)

Conversions ​

Set ​

A set represents a collection of unique unordered values with hashing.

2 in { "a", 2, true } #=> true
let s = set()
s | push(5)

2 in { "a", 2, true } #=> true
let s = set()
s | push(5)

String ​

Strings represent text values and are created by surrounding text with double quotes or single quotes. Backslashes are used to escape characters. However, in single quote literals, it is only possible to escape single quotes. String operations are done immutably, but some standard library functions may result in mutation.

Conversions ​

Escape Sequences ​

Interpolation ​

String interpolation is done by surrounding code with braces preceded by a dollar sign in a string literal, for example "Value: ${x + 1}". This is only possible with double quote strings. Environment variables can also be interpolated, for example Var: $VAR.

Iteration ​

Iterating over a string yields each character in the string, one by one.

Tuple ​

A tuple is an immutable data structure containing values. A tuple is created by surrounding comma-separated values with parentheses.

let a, b = (1, 2)

let a, b = (1, 2)

Conversions ​

Type ​

A type in Elk is a static value that represents a data type. It is created by writing the name of the data type.

assert("some string" | isType(String))
let dataType = Integer;

assert("some string" | isType(String))
let dataType = Integer;

Conversions ​