12 KiB
this is a WIP based on Builtins.bend.
Built-in Types and Functions
Bend built-in types and functions, this document serves as a reference guide. Read more at FEATURES.md.
String
type String = (Cons head ~tail) | (Nil)
- Nil: Represents an empty string.
- Cons head ~tail: Represents a string with a
head
character and atail
string.
Syntax
A String literal is surrounded with "
. Accepts the same values as characters literals.
"Hello, World!"
List
type List = (Cons head ~tail) | (Nil)
- Nil: Represents an empty list.
- Cons head ~tail: Represents a list with a
head
element and atail
list.
Syntax
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"]
Functions
List/length
def List/length(list: [a]) -> (length: u24, list: [a])
Returns a tuple containing the length and the list itself.
List/reverse
def List/reverse(list: [a]) -> [a]
Reverses the elements of a list.
List/flatten
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]
List/concat
def List/concat(xs: [a], ys: [a]) -> [a]
Appends two lists together. Example:
List/concat([1, 2], [4, 5])
# Result: [1, 2, 4, 5]
Tree
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
.
Syntax
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.
Map
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.
Syntax
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
.
Map functions
Map/empty
Initializes an empty map.
Map/empty = Map/Leaf
Map/get
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)
}
}
Syntax
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"
Map/set
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)
}
}
Syntax
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"}
Map/map
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)
}
Syntax
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"
Nat
type Nat = (Succ ~pred) | (Zero)
- Succ ~pred: Represents a natural number successor.
- Zero: Represents the natural number zero.
Syntax
A Natural Number can be written with literals with a #
before the literal number.
#1337
IO
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.
Printing
def IO/print(text)
Prints the string text
to the standard output, encoded with utf-8.
Input
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.
File IO
File open
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.
File descriptors for standard files
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
File close
def IO/FS/close(file)
Closes the file with the given file
descriptor.
File read
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.
File write
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
.
File seek
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 (*
).
Numeric operations
log
def log(x: f24, base: f24) -> f24
Computes the logarithm of x
with the specified base
.
atan2
def atan2(x: f24, y: f24) -> f24
Computes the arctangent of y / x
.
Has the same behaviour as atan2f
in the C math lib.
to_f24
def to_f24(x: any number) -> f24
Casts any native number to an f24.
to_u24
def to_u24(x: any number) -> u24
Casts any native number to a u24.
to_i24
def to_i24(x: any number) -> i24
Casts any native number to an i24.
String encoding / decoding
Bytes/decode_utf8
def Bytes/decode_utf8(bytes: [u24]) -> String
Decodes a sequence of bytes to a String using utf-8 encoding.
Bytes/decode_ascii
def Bytes/decode_ascii(bytes: [u24]) -> String
Decodes a sequence of bytes to a String using ascii encoding.
String/encode_utf8
def String/encode_utf8(s: String) -> [u24]
Encodes a String to a sequence of bytes using utf-8 encoding.
String/encode_ascii
def String/encode_ascii(s: String) -> [u24]
Encodes a String to a sequence of bytes using ascii encoding.
Utf8/decode_character
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.
Utf8/REPLACEMENT_CHARACTER
def Utf8/REPLACEMENT_CHARACTER: u24 = '\u{FFFD}'
Math
Math/PI
Defines the Pi constant.
def Math/PI: f24 = 3.1415926535
Math/sin
Computes the sine of the given angle in radians.
def Math/sin(a: f24) -> f24
Math/cos
Computes the cosine of the given angle in radians.
def Math/cos(a: f24) -> f24
Math/tan
Computes the tangent of the given angle in radians.
def Math/tan(a: f24) -> f24
Math/cot
Computes the cotangent of the given angle in radians.
def Math/cot(a: f24) -> f24
Math/sec
Computes the secant of the given angle in radians.
def Math/sec(a: f24) -> f24
Math/csc
Computes the cosecant of the given angle in radians.
def Math/csc(a: f24) -> f24
Math/radians
Converts degrees to radians.
def Math/radians(a: f24) -> f24
Math/sqrt
Computes the square root of the given number.
def Math/sqrt(n: f24) -> f24
Math/ceil
Round float up to the nearest integer.
def Math/ceil(n: f24) -> f24
Math/floor
Round float down to the nearest integer.
def Math/floor(n: f24) -> f24