Olle Jonsson's blog

[Io](http://www.iolanguage.com/)’s very self-documenting, at least when it comes to “what parameters does this and that take?” This is a little walk-through that gets you up and running in the interpreter. Get a binary from the downlaods page, and then come back here.

There is a docs slot — with some text about what the method does. First, let’s list a string (in Io, known as a Sequence, a sequence of characters, you know).

Whip out your Io interpreter, and write a string, and send the docs message to it:

Io> "olle" docs

==>  Object_0x6d5020:
  slots            = Object_0x6d5060

There we go, a memory address for the docs, and a list of slots. Open that!

Io> "olle" docs slots

==>  Object_0x6d5060:
  alignCenter      = Object_0x1120d90
  alignLeft        = Object_0x111fcf0
  alignLeftInPlace = Object_0x111e810
  alignRight       = Object_0x1120530
  findNthSeq       = Object_0x1121870
  interpolate      = Object_0x11222f0
  interpolateInPlace = Object_0x11226f0
  removeSeq        = Object_0x111f2d0
  repeated         = Object_0x6d4880

These contain documentation:

Io> "olle" docs slots repeated

==>  Object_0x6d4880:
  args             = List_0x6d4e20
  description      = "Returns a new sequence containing the receiver repeated aNumber number of times."

That is nice. But, there are many more methods on a Sequence. Where are the rest? Answer: not yet documented like this. Let’s go find the others.

Io> Sequence slotSummary

==>  "":
  ..               = method(arg, ...)
  afterSeq         = Sequence_afterSeq()
  alignCenter      = method(width, padding, ...)
  alignLeft        = method(width, padding, ...)
  alignLeftInPlace = method(width, padding, ...)
  alignRight       = method(width, padding, ...)
  append           = Sequence_append()
  appendPathSeq    = Sequence_appendPathSeq()
  appendSeq        = Sequence_appendSeq()
  asBinaryNumber   = Sequence_asBinaryNumber()
  asBuffer         = Sequence_asBuffer()
  asCapitalized    = Sequence_asCapitalized()
  asLowercase      = Sequence_asLowercase()
  asMessage        = Sequence_asMessage()
  asMutable        = Sequence_asMutable()
  asNumber         = Sequence_asNumber()
  asSimpleString   = method(...)
  asString         = Sequence_asString()
  asSymbol         = Sequence_asSymbol()
  asUppercase      = Sequence_asUppercase()
  at               = Sequence_at()
  atInsertSeq      = Sequence_atInsertSeq()
  atPut            = Sequence_atPut()
--- SNIPPED, FOR HER PLEASURE ---

That’s more like it! Notice the difference in the right-hand listing.

asNumber         = Sequence_asNumber()
asSimpleString   = method(...)

asNumber has a fast C implementation (the function name is a hint there), but asSimpleString is pure Io.

The Io-implemented methods have their argument list with them, like alignRight. The ellipsis (…) stands for the method body.

It’s possible to return any Io slot, serialized as a string. That includes all Io-implemented methods! Use the getSlot() method:

Io> Sequence alignRight getSlot("serialized")

==> method(b, if(b ==(nil), setSlot("b", Sequence clone));
b appendSeq(self asMutable replaceSeq("\"", "\\\"") asSimpleString))

So, Io has some documentation, and you can read much of the code in the interpreter.

The [online reference docs](http://iolanguage.com/docs/reference/browser.cgi) are not to be trusted, but they are helpful at times.