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This chapter describes builtin functions (as opposed to builtin commands.)

(in progress)

Values

len()

Returns the

• number of entries in a List
• number of pairs in a Dict
• number of bytes in a Str
  • TODO: countRunes() can return the number of UTF-8 encoded code points.

func/type()

Given an arbitrary value, returns a string representing the value's runtime type.

For example:

var d = {'foo': 'bar'}
var n = 1337

$ = type(d)
(Str)    'Dict'

$ = type(n)
(Str)    'Int'

Similar names: type

Conversions

bool()

Returns the truth value of its argument. Similar to bool() in python, it returns false for:

• false, 0, 0.0, '', {}, [], and null.

Returns true for all other values.

int()

Given a float, returns the largest integer that is less than its argument (i.e. floor()).

$ = int(1.99)
(Int)    1

Given a string, Int() will attempt to convert the string to a base-10 integer. The base can be overridden by calling with a second argument.

$ = int('10')
(Int)   10

$ = int('10', 2)
(Int)   2

ysh$ = Int('foo')
# fails with an expression error

float()

Given an integer, returns the corresponding floating point representation.

$ = float(1)
(Float)   1.0

Given a string, Float() will attempt to convert the string to float.

$ = float('1.23')
(Float)   1.23

ysh$ = float('bar')
# fails with an expression error

str()

Converts a Float or Int to a string.

list()

Given a list, returns a shallow copy of the original.

Given an iterable value (e.g. a range or dictionary), returns a list containing one element for each item in the original collection.

$ = list({'a': 1, 'b': 2})
(List)   ['a', 'b']

$ = list(1:5)
(List)   [1, 2, 3, 4, 5]

dict()

Given a dictionary, returns a shallow copy of the original.

runes()

TODO

Given a string, decodes UTF-8 into a List of integer "runes" (aka code points).

Each rune is in the range U+0 to U+110000, and excludes the surrogate range.

runes(s, start=-1, end=-1)

TODO: How do we signal errors?

(runes() can be used to implement implemented Python's ord().)

encodeRunes()

TODO

Given a List of integer "runes" (aka code points), return a string.

(encodeRunes() can be used to implement implemented Python's chr().)

bytes()

TODO

Given a string, return a List of integer byte values.

Each byte is in the range 0 to 255.

encodeBytes()

TODO

Given a List of integer byte values, return a string.

Str

strcmp()

TODO

shSplit()

Split a string into a List of strings, using the shell algorithm that respects $IFS.

Prefer split() to shSplit().

List

join()

Given a List, stringify its items, and join them by a separator. The default separator is the empty string.

var x = ['a', 'b', 'c']

$ echo $[join(x)]
abc

$ echo $[join(x, ' ')]  # optional separator
a b c

It's also often called with the => chaining operator:

var items = [1, 2, 3]

json write (items => join())      # => "123"
json write (items => join(' '))   # => "1 2 3"
json write (items => join(', '))  # => "1, 2, 3"

Dict

keys()

Returns all existing keys from a dict as a list of strings.

var en2fr = {
  hello: "bonjour",
  friend: "ami",
  cat: "chat"
}
= keys(en2fr)
# => (List 0x4689)   ["hello","friend","cat"]

values()

Similar to keys(), but returns the values of the dictionary.

var person = {
  name: "Foo",
  age: 25,
  hobbies: :|walking reading|
}
= values(en2fr)
# => (List 0x4689)   ["Foo",25,["walking","reading"]]

get()

Return value for given key, falling back to the default value if the key doesn't exist.

var book = {
  title: "Hitchhiker's Guide",
  published: 1979,
}

var published = get(book, 'published', null)
= published
# => (Int)   1979

var author = get(book, 'author', "???")
= author
# => (Str)   "???"

If not specified, the default value is null:

var author = get(book, 'author')
= author
# => (Null)   null

Float

floatsEqual()

Check if two floating point numbers are equal.

= floatsEqual(42.0, 42.0)
(Bool)   true

It's usually better to make an approximate comparison:

= abs(float1 - float2) < 0.001
(Bool)   false

Obj

first()

Get the Dict that contains an object's properties.

ysh$ = first(obj)
(Dict)  {x: 42}

The Dict and Obj share the same storage. So if the Dict is modified, the object is too.

If you want a copy, use dict(obj).

rest()

Get the "prototype" of an Obj, which is another Obj, or null:

ysh$ = rest(obj)
(Null)  null

Word

glob()

See glob-pat topic for syntax.

maybe()

Serialize

toJson()

Convert an object in memory to JSON text:

$ = toJson({name: "alice"})
(Str)   '{"name":"alice"}'

Add indentation by passing the space param:

$ = toJson([42], space=2)
(Str)   "[\n  42\n]"

Similar to json write (x), except the default value of space is 0.

See err-json-encode for errors.

fromJson()

Convert JSON text to an object in memory:

= fromJson('{"name":"alice"}')
(Dict)   {"name": "alice"}

Similar to json read <<< '{"name": "alice"}'.

See err-json-decode for errors.

toJson8()

Like toJson(), but it also converts binary data (non-Unicode strings) to J8-style b'foo \yff' strings.

In contrast, toJson() will do a lossy conversion with the Unicode replacement character.

See err-json8-encode for errors.

fromJson8()

Like fromJson(), but it also accepts binary data denoted by J8-style b'foo \yff' strings.

See err-json8-decode for errors.

Pattern

_group()

Like Match => group(), but accesses the global match created by ~:

if ('foo42' ~ / d+ /) {
  echo $[_group(0)]  # => 42
}

_start()

Like Match => start(), but accesses the global match created by ~:

if ('foo42' ~ / d+ /) {
  echo $[_start(0)]  # => 3
}

_end()

Like Match => end(), but accesses the global match created by ~:

if ('foo42' ~ / d+ /) {
  echo $[_end(0)]  # => 5
}

Introspect

shvarGet()

Given a variable name, return its value. It uses the "dynamic scope" rule, which looks up the stack for a variable.

It's meant to be used with shvar:

proc proc1 {
  shvar PATH=/tmp {  # temporarily set PATH in this stack frame
    my-proc
  }

  proc2
}

proc proc2 {
  proc3
}

proc proc3 {
  var path = shvarGet('PATH')  # Look up the stack (dynamic scoping)
  echo $path  # => /tmp
}

proc1

Note that shvar is usually for string variables, and is analogous to shopt for "booleans".

If the variable isn't defined, shvarGet() returns null. So there's no way to distinguish an undefined variable from one that's null.

getVar()

Given a variable name, return its value.

$ var x = 42
$ echo $[getVar('x')]
42

The variable may be local or global. (Compare with shvarGet().) the "dynamic scope" rule.)

If the variable isn't defined, getVar() returns null. So there's no way to distinguish an undefined variable from one that's null.

setVar()

Bind a name to a value, in the local scope. Returns nothing.

call setVar('myname', 42)

This is like

setvar myname = 42

except the name can is a string, which can be constructed at runtime.

parseCommand()

Given a code string, parse it as a command (with the current parse options).

Returns a value.Command instance, or raises an error.

parseExpr()

TODO:

Given a code string, parse it as an expression.

Returns a value.Expr instance, or raises an error.

Hay Config

parseHay()

evalHay()

Hashing

sha1dc()

Git's algorithm.

sha256()