this is a WIP based on Builtins.bend.
Bend built-in types and functions, this document serves as a reference guide. Read more at FEATURES.md.
type String = (Cons head ~tail) | (Nil)
- Nil: Represents an empty string.
- Cons head ~tail: Represents a string with a
head
character and atail
string.
A String literal is surrounded with "
. Accepts the same values as characters literals.
"Hello, World!"
type List = (Cons head ~tail) | (Nil)
- Nil: Represents an empty list.
- Cons head ~tail: Represents a list with a
head
element and atail
list.
A List of values can be written using [ ]
, it can have multiple values inside, using ,
you can divide its value in a list of multiple elements.
["This", "List", "Has", "Multiple", "Values"]
def List/length(list: [a]) -> (length: u24, list: [a])
Returns a tuple containing the length and the list itself.
def List/reverse(list: [a]) -> [a]
Reverses the elements of a list.
def List/flatten(list: [[a]]) -> [a]
Returns a flattened list from a list of lists. Example:
List/flatten([[1], [2, 3], [4]])
# Result: [1, 2, 3, 4]
def List/concat(xs: [a], ys: [a]) -> [a]
Appends two lists together. Example:
List/concat([1, 2], [4, 5])
# Result: [1, 2, 4, 5]
type Tree:
Node { ~left, ~right }
Leaf { value }
Tree
represents a tree with values stored in the leaves.
Trees are a structure that naturally lends itself to parallel recursion, so writing your problem in terms of trees is a good first approach to parallelize your code.
- Node { ~left ~right }: Represents a tree node with
left
andright
subtrees. - Leaf { value }: Represents one of the ends of the tree, storing
value
.
Bend provides the ![]
operator to create tree branches and the !
operator to create a tree leaf.
# ![a, b] => Equivalent to Tree/Node { left: a, right: b }
# !x => Equivalent to Tree/Leaf { value: x }
tree = ![![!1, !2],![!3, !4]]
Technically your trees don't need to end with leaves, but if you don't, your program will be very hard to reason about.
type Map:
Node { value ~left ~right }
Leaf
Map
represents a tree with values stored in the branches.
It is meant to be used as an efficient map data structure with integer keys and O(log n) read and write operations.
- Node { value ~left ~right }: Represents a map node with a
value
andleft
andright
subtrees. Empty nodes have*
stored in thevalue
field. - Leaf: Represents an unwritten, empty portion of the map.
Here's how you create a new Map
with some initial values.:
{ 0: 4, `hi`: "bye", 'c': 2 + 3 }
The keys must be U24
numbers, and can be given as literals or any other expression that evaluates to a U24
.
The values can be anything, but storing data of different types in a Map
will make it harder for you to reason about it.
You can read and write a value of a map with the []
operator:
map = { 0: "zero", 1: "one", 2: "two", 3: "three" }
map[0] = "not zero"
map[1] = 2
map[2] = 3
map[3] = map[1] + map[map[1]]
Here, map
must be the name of the Map
variable, and the keys inside []
can be any expression that evaluates to a U24
.
Initializes an empty map.
Map/empty = Map/Leaf
Retrieves a value
from the map
based on the key
.
Returns a tuple with the value and the map
unchanged.
Map/get map key =
match map {
Map/Leaf: (*, map)
Map/Node:
switch _ = (== 0 key) {
0: switch _ = (% key 2) {
0:
let (got, rest) = (Map/get map.left (/ key 2))
(got, (Map/Node map.value rest map.right))
_:
let (got, rest) = (Map/get map.right (/ key 2))
(got, (Map/Node map.value map.left rest))
}
_: (map.value, map)
}
}
Considering the following map
{ 0: "hello", 1: "bye", 2: "maybe", 3: "yes"}
The get
function can be written as
return x[0] # Gets the value of the key 0
And the value resultant from the get function would be:
"hello"
Sets a value
in the map
at the specified key
.
Returns the map with the new value.
Map/set map key value =
match map {
Map/Node:
switch _ = (== 0 key) {
0: switch _ = (% key 2) {
0: (Map/Node map.value (Map/set map.left (/ key 2) value) map.right)
_: (Map/Node map.value map.left (Map/set map.right (/ key 2) value))
}
_: (Map/Node value map.left map.right)
}
Map/Leaf:
switch _ = (== 0 key) {
0: switch _ = (% key 2) {
0: (Map/Node * (Map/set Map/Leaf (/ key 2) value) Map/Leaf)
_: (Map/Node * Map/Leaf (Map/set Map/Leaf (/ key 2) value))
}
_: (Map/Node value Map/Leaf Map/Leaf)
}
}
Considering the following tree
{ 0: "hello", 1: "bye", 2: "maybe", 3: "yes"}
The set
function can be written as
x[0] = "swapped" # Assigns the key 0 to the value "swapped"
And the value resultant from the get function would be:
{ 0: "swapped", 1: "bye", 2: "maybe", 3: "yes"}
If there's no matching key
in the tree, it would add a new branch to that tree with the value set
x[4] = "added" # Assigns the key 4 to the value "added"
The new tree
{ 0: "swapped", 1: "bye", 2: "maybe", 3: "yes", 4: "added"}
Applies a function to a value in the map. Returns the map with the value mapped.
Map/map (Map/Leaf) key f = Map/Leaf
Map/map (Map/Node value left right) key f =
switch _ = (== 0 key) {
0: switch _ = (% key 2) {
0:
(Map/Node value (Map/map left (/ key 2) f) right)
_:
(Map/Node value left (Map/map right (/ key 2) f))
}
_: (Map/Node (f value) left right)
}
With the same map that we set
in the previous section, we can map it's values with @=
:
x[0] @= lambda y: String/concat(y, " and mapped")
# x[0] now contains "swapped and mapped"
type Nat = (Succ ~pred) | (Zero)
- Succ ~pred: Represents a natural number successor.
- Zero: Represents the natural number zero.
A Natural Number can be written with literals with a #
before the literal number.
#1337
The basic builtin IO functions are under development and will be stable in the next milestone.
Here is the current list of functions, but be aware that they may change in the near future.
def IO/print(text)
Prints the string text
to the standard output, encoded with utf-8.
def IO/input() -> String
Reads characters from the standard input until a newline is found.
Returns the read input as a String decoded with utf-8.
def IO/FS/open(path, mode)
Opens a file with with path
being given as a string and mode
being a string with the mode to open the file in. The mode should be one of the following:
"r"
: Read mode"w"
: Write mode (write at the beginning of the file, overwriting any existing content)"a"
: Append mode (write at the end of the file)"r+"
: Read and write mode"w+"
: Read and write mode"a+"
: Read and append mode
Returns an U24 with the file descriptor. File descriptors are not necessarily the same as the ones assigned by the operating system, but rather unique identifiers internal to Bend's runtime.
The standard input/output files are always open and assigned the following file descriptors:
IO/FS/STDIN = 0
: Standard inputIO/FS/STDOUT = 1
: Standard outputIO/FS/STDERR = 2
: Standard error
def IO/FS/close(file)
Closes the file with the given file
descriptor.
def IO/FS/read(file, num_bytes)
Reads num_bytes
bytes from the file with the given file
descriptor.
Returns a list of U24 with each element representing a byte read from the file.
def IO/FS/read_line(file)
Reads a line from the file with the given file
descriptor.
Returns a list of U24 with each element representing a byte read from the file.
def IO/FS/read_until_end(file)
Reads until the end of the file with the given file
descriptor.
Returns a list of U24 with each element representing a byte read from the file.
def IO/FS/read_file(path)
Reads an entire file with the given path
and returns a list of U24 with each element representing a byte read from the file.
def IO/FS/write(file, bytes)
Writes bytes
, a list of U24 with each element representing a byte, to the file with the given file
descriptor.
Returns nothing (*
).
def IO/FS/write_file(path, bytes)
Writes bytes
, a list of U24 with each element representing a byte, as the entire content of the file with the given path
.
def IO/FS/seek(file, offset, mode)
Moves the current position of the file with the given file
descriptor to the given offset
, an I24 or U24 number, in bytes.
mode
can be one of the following:
IO/FS/SEEK_SET = 0
: Seek from start of fileIO/FS/SEEK_CUR = 1
: Seek from current positionIO/FS/SEEK_END = 2
: Seek from end of file
Returns nothing (*
).
def log(x: f24, base: f24) -> f24
Computes the logarithm of x
with the specified base
.
def atan2(x: f24, y: f24) -> f24
Computes the arctangent of y / x
.
Has the same behaviour as atan2f
in the C math lib.
def to_f24(x: any number) -> f24
Casts any native number to an f24.
def to_u24(x: any number) -> u24
Casts any native number to a u24.
def to_i24(x: any number) -> i24
Casts any native number to an i24.
def Bytes/decode_utf8(bytes: [u24]) -> String
Decodes a sequence of bytes to a String using utf-8 encoding.
def Bytes/decode_ascii(bytes: [u24]) -> String
Decodes a sequence of bytes to a String using ascii encoding.
def String/encode_utf8(s: String) -> [u24]
Encodes a String to a sequence of bytes using utf-8 encoding.
def String/encode_ascii(s: String) -> [u24]
Encodes a String to a sequence of bytes using ascii encoding.
def Utf8/decode_character(bytes: [u24]) -> (rune: u24, rest: [u24])
Decodes a utf-8 character, returns a tuple containing the rune and the rest of the byte sequence.
def Utf8/REPLACEMENT_CHARACTER: u24 = '\u{FFFD}'