Pipes

A pipe is a self-operator that transforms a value in place. The colon notation receiver:name(args) looks up the function name in the pipe table and calls it with the receiver injected as the first argument:

receiver:name(args)  ==  receiver = name(receiver, args)

Two important properties:

• The result is assigned back to the receiver, so pipes read naturally as in-place transformations: s:trim():upper() trims then uppercases s.
• The return type must match the receiver's type. A pipe that returns a different type raises a TYPE_ERROR.

Pipes resolve through the pipe table and the global/std scope, never through the receiver's own members — a function stored in an object is called with dot (obj.fn(...), where the receiver is not passed).

var s  = "  hello  "
s:trim():upper()        // s -> "HELLO"

var arr = [3, 1, 2]
arr:sort():reverse()    // arr -> [3, 2, 1]

var obj = {a: 1}
obj:merge({b: 2})       // obj -> {a: 1, b: 2}

print("abc":upper())    // error: literals cannot be receivers

The pipe builtins

pipe(name, fn) registers a callable name in the pipe table. From then on, receiver:name(args) calls fn(receiver, args).

pipe_remove(name) unregisters it and returns true if it was removed:

pipe("double", fn(n) { return n * 2 })

var x = 21
x:double()              // x -> 42

print(pipe_remove("double"))   // true
// x:double()           // error: unknown pipe 'double'

Initially available pipes

The built-in pipe table is seeded with a curated set of standard library functions:

Strings

upper  lower  trim  trim_left  trim_right
substr  replace  replace_first  repeat  pad_left  pad_right

Arrays (from std.sort and std.seq)

sort  sort_by  shuffle  unique  flatten  slice  concat  fill
map  filter  find_all  zip
take  drop  chunk  enumerate
set_union  set_intersect  set_difference

Objects

merge

Dispatch pipes — work on more than one receiver type:

insert   // strings, arrays, objects
erase    // strings, arrays, objects
reverse  // strings, arrays

var s = "hello"
s:insert(1, "X")        // s -> "hXello"

var n = [1, 2, 3]
n:erase(1)              // n -> [1, 3]

var w = "abc"
w:reverse()             // w -> "cba"

note

Not every std.* function is available as a pipe — only the ones seeded above (plus anything you register). To call any other library function use the dot form, e.g. std.string.split(s, ",").