[IoLanguage]Io Programming Guide[转]

Io Programming Guide

Introduction

Overview

Perspective

In Io, all values are objects (of which, anything can change at runtime, including slots, methods and inheritance), all code is made up of expressions (which are runtime inspectable and modifiable) and all expressions are made up of dynamic message sends (including assignment and control structures). Execution contexts themselves are objects and activatable objects such as methods/blocks and functions are unified into blocks with assignable scope. Concurrency is made more easily manageable through actors and implemented using coroutines for scalability.

Goals

simple

• conceptually simple and consistent
• easily embedded and extended

powerful

• highly dynamic and introspective
• highly concurrent (via coroutines and async i/o)

practical

• fast enough
• multi-platform
• unrestrictive BSD/MIT license
• comprehensive standard packages in distro

Downloading

Installing

make vm

sudo make install

Installing Addon Dependencies

Some of Io's addons require libraries that may not be installed on your system already. To install these automatically, type either:

su -c "sudo make aptget"

or:

su -c "make emerge"

or:

sudo make port

Depending on which package installer you use. (port is for OSX)

Compiling Addons

To build, from the top folder, run:

make

Binaries will be placed in the _build/binaries subfolder. To install:

sudo make install

or, if you'd like the install to simply link to your development folder:

sudo make linkInstall

and to run all unit tests:

make test

Don't worry if some of the addons won't build unless it's a particular addon that you need. Addons are just optional libraries.

Notes

To make a particular addon, you can do:

make AddonName

After doing a pull from the source control repo, be sure to do:

make clean; make

To test just the vm:

make testvm

And to update the reference documentation (found in docs/IoReference.html) from the source code:

make doc

Binaries

io_static

io

The io_static executable contains the vm with a minimal set of primitives all statically linked into the executable. The io executable contains just enough to load the iovm dynamically linked library and is able to dynamically load io addons when they are referenced.

Running Scripts

io samples/misc/HelloWorld.io

There is no main() function or object that gets executed first in Io. Scripts are executed when compiled.

Interactive Mode

./_build/binaries/io

Or, if Io is installed, running:

io

will open the Io interpreter prompt.

You can evaluate code by entering it directly. Example:

Io> "Hello world!" println

==> Hello world!

Expressions are evaluated in the context of the Lobby:

Io> print

[printout of lobby contents]

If you have a .iorc file in your home folder, it will be evaled before the interactive prompt starts.

Inspecting objects

Io> someObject slotNames

To show them in sorted order:

Io> someObject slotNames sort

For a nicely formatted description of an object, the slotSummary method is handy:

Io> slotSummary

==>  Object_0x20c4e0:

  Lobby            = Object_0x20c4e0

  Protos           = Object_0x20bff0

  exit             = method(...)

  forward          = method(...)

Exploring further:

Io> Protos

==>  Object_0x20bff0:

  Addons           = Object_0x20c6f0

  Core             = Object_0x20c4b0

Io> Protos Addons

==>  Object_0x20c6f0:

  ReadLine         = Object_0x366a10

Only ReadLine is seen in the Addons since no other Addons have been loaded yet.

Inspecting a method will print a decompiled version of it:

Io> Lobby getSlot("forward")

==> # io/Z_Importer.io:65

method(

    Importer import(call)

)

doFile and doString

A script can be run from the interactive mode using the doFile method:

doFile("scriptName.io")

The evaluation context of doFile is the receiver, which in this case would be the lobby. To evaluate the script in the context of some other object, simply send the doFile message to it:

someObject doFile("scriptName.io")

The doString method can be used to evaluate a string:

Io> doString("1+1")

==> 2

And to evaluate a string in the context of a particular object:

someObject doString("1 + 1")

Command Line Arguments

Example of printing out command line arguments:

System args foreach(k, v, write("'", v, "'\n"))

launchPath

The System "launchPath" slot is set to the location of the initial source file that is executed; when the interactive prompt is started (without specifying a source file to execute), the launchPath is the current working directory:

System launchPath

Syntax

Expressions

exp        ::= { message | terminator }

message    ::= symbol [arguments]

arguments  ::= "(" [exp [ { "," exp } ]] ")"

symbol     ::= identifier | number | string

terminator ::= "\n" | ";"

For performance reasons, String and Number literal messages have their results cached in their message objects.

Messages

for(i, 1, 10, i println)

a := if(b == 0, c + 1, d)

In the above code, "for" and "if" are just normal messages, not special forms or keywords.

Likewise, dynamic evaluation can be used with enumeration without the need to wrap the expression in a block. Examples:

people select(person, person age < 30)

names := people map(person, person name)

Methods like map and select will typically apply the expression directly to the values if only the expression is provided:

people select(age < 30)

names := people map(name)

There is also some syntax sugar for operators (including assignment), which are handled by an Io macro executed on the expression after it is compiled into a message tree. Some sample source code:

Account := Object clone

Account balance := 0

Account deposit := method(amount,

    balance = balance + amount

)

account := Account clone

account deposit(10.00)

account balance println

Like Self[2], Io's syntax does not distinguish between accessing a slot containing a method from one containing a variable.

Operators

1 + 2

This just gets compiled into the normal message:

1 +(2)

Which is the form you can use if you need to do grouping:

1 +(2 * 4)

Standard operators follow C's precedence order, so:

1 + 2 * 3 + 4

Is parsed as:

1 +(2 *(3)) +(4)

User defined operators (that don't have a standard operator name) are performed left to right.

Assignment

These operators are compiled to normal messages whose methods can be overridden. For example:

On Locals objects, updateSlot is overridden so it will update the slot in the object in which the method was activated if the slot is not found the locals. This is done so update assignments in methods don't require self to be an explicit target.

Numbers

123

123.456

0.456

.456

123e-4

123e4

123.456e-7

123.456e2

Hex numbers are also supported (in any casing):

0x0

0x0F

0XeE

Strings

s := "this is a \"test\".\nThis is only a test."

Or for strings with non-escaped characters and/or spanning many lines, triple quotes can be used.

s := """this is a "test".

This is only a test."""

Comments

a := b // add a comment to a line

/* comment out a group

a := 1

b := 2

*/

The "#" style is useful for unix scripts:

#!/usr/local/bin/io

That's it! You now know everything there is to know about Io's syntax. Control flow, objects, methods, exceptions are expressed with the syntax and semantics described above.

Objects

Overview

Prototypes

clone and init

New objects are made by cloning existing ones. A clone is an empty object that has the parent in its list of protos. A new instance's init slot will be activated which gives the object a chance to initialize itself. Like NewtonScript[3], slots in Io are create-on-write.

me := Person clone

To add an instance variable or method, simply set it:

myDog name := "rover"

myDog sit := method("I'm sitting\n" print)

When an object is cloned, its "init" slot will be called if it has one.

Inheritance

Since there are no classes, there's no difference between a subclass and an instance. Here's an example of creating the equivalent of a subclass:

Io> Dog := Object clone

==> Object_0x4a7c0

The above code sets the Lobby slot "Dog" to a clone of the Object object; the protos list of this new object contains only a reference to Object, essentially indicating that a subclass of Object has been created. Instance variables and methods are inherited from the objects referenced in the protos list. If a slot is set, it creates a new slot in our object instead of changing the protos:

  Io> Dog color := "red"

  Io> Dog

  ==> Object_0x4a7c0:

    color := "red"

Multiple Inheritance

You can add any number of protos to an object's protos list. When responding to a message, the lookup mechanism does a depth first search of the proto chain.

Methods

method((2 + 2) print)

An example of using a method in an object:

Dog := Object clone

Dog bark := method("woof!" print)

The above code creates a new "subclass" of object named Dog and adds a bark slot containing a block that prints "woof!". Example of calling this method:

Dog bark

The default return value of a block is the result of the last expression.

Arguments

Methods can also be defined to take arguments. Example:

add := method(a, b, a + b)

The general form is:

method(<arg name 0>, <arg name 1>, ..., <do message>)

Blocks

b := block(a, a + b)

Blocks vs. Methods

This is sometimes a source of confusion so it's worth explaining in detail. Both methods and blocks create an object to hold their locals when they are called. The difference is what the "proto" and "self" slots of that locals object are set to. In a method, those slots are set to the target of the message. In a block, they're set to the locals object where the block was created. So a failed variable lookup in a block's locals continue in the locals where it was created. And a failed variable lookup in a method's locals continue in the object to which the message that activated it was sent.

call and self slots

When a locals object is created, its self slot is set (to the target of the message, in the case of a method, or to the creation context, in the case of a block) and its call slot is set to a Call object that can be used to access information about the block activation:

Variable Arguments

The "call message" slot in locals can be used to access the unevaluated argument messages. Example of implementing if() within Io:

myif := method(

    (call sender doMessage(call message argAt(0))) ifTrue(

    call sender doMessage(call message argAt(1))) ifFalse(

    call sender doMessage(call message argAt(2)))

)

myif(foo == bar, write("true\n"), write("false\n"))

The doMessage() method evaluates the argument in the context of the receiver. A shorter way to express this is to use the evalArgAt() method on the call object:

myif := method(

    call evalArgAt(0) ifTrue(

    call evalArgAt(1)) ifFalse(

    call evalArgAt(2))

)

myif(foo == bar, write("true\n"), write("false\n"))

Forward

MyObject forward := method(

    write("sender = ", call sender, "\n")

    write("message name = ", call message name, "\n")

    args := call message argsEvaluatedIn(call sender)

    args foreach(i, v, write("arg", i, " = ", v, "\n") )

)

Resend

A := Object clone

A m := method(write("in A\n"))

B := A clone

B m := method(write("in B\n"); resend)

B m

will print:

in B

in A

For sending other messages to the receiver's proto, super is used.

Super

Dog := Object clone

Dog bark := method(writeln("woof!"))

fido := Dog clone

fido bark := method(

    writeln("ruf!")

    super(bark)

)

Both resend and super are implemented in Io.

Introspection

slotNames

The slotNames method returns a list of the names of an object's slots:

Io> Dog slotNames

==> list("bark")

protos

The protos method returns a list of the objects which an object inherits from:

Io> Dog protos

==> list("Object")

getSlot

The "getSlot" method can be used to get the value of a block in a slot without activating it:

myMethod := Dog getSlot("bark")

Above, we've set the locals object's "myMethod" slot to the bark method. It's important to remember that if you then want use the myMethod without activating it, you'll need to use the getSlot method:

otherObject newMethod := getSlot("myMethod")

Here, the target of the getSlot method is the locals object.

code

The arguments and expressions of methods are open to introspection. A useful convenience method is "code", which returns a string representation of the source code of the method in a normalized form.

Io> method(a, a * 2) code

==> "method(a, a *(2))"

Control Flow

true, false and nil

Comparison

==, !=, >=, <=, >, <

return either the true or false. The compare() method is used to implement the comparison methods and returns -1, 0 or 1 which mean less-than, equal-to or greater-than, respectively.

if, then, else

if(<condition>, <do message>, <else do message>)

Example:

if(a == 10, "a is 10" print)

The else argument is optional. The condition is considered false if the condition expression evaluates to false or nil, and true otherwise.

The result of the evaluated message is returned, so:

if(y < 10, x := y, x := 0)

is the same as:

x := if(y < 10, y, 0)

Conditions can also be used in this form:

if(y < 10) then(x := y) else(x := 2)

elseif() is supported:

if(y < 10) then(x := y) elseif(y == 11) then(x := 0) else(x := 2)

ifTrue, ifFalse

(y < 10) ifTrue(x := y) ifFalse(x := 2)

Notice that the condition expression must have parenthesis surrounding it.

loop

loop("foo" println)

repeat

3 repeat("foo" print)

==> foofoofoo

while

while(<condition>, <do message>)

Example:

a := 1

while(a < 10,

    a print

    a = a + 1

)

for

for(<counter>, <start>, <end>, <optional step>, <do message>)

The start and end messages are only evaluated once, when the loop starts. Example:

for(a, 0, 10,

    a println

)

Example with a step:

for(x, 0, 10, 3, x println)

Which would print:

0

3

6

9

To reverse the order of the loop, add a negative step:

for(a, 10, 0, -1, a println)

Note: the first value will be the first value of the loop variable and the last will be the last value on the final pass through the loop. So a loop of 1 to 10 will loop 10 times and a loop of 0 to 10 will loop 11 times.

break, continue

for(i, 1, 10,

    if(i == 3, continue)

    if(i == 7, break)

    i print

)

Output:

12456

return

Io> test := method(123 print; return "abc"; 456 print)

Io> test

123

==> abc

Internally, break, continue and return all work by setting a IoState internal variable called "stopStatus" which is monitored by the loop and message evaluation code.

Importing

Concurrency

Coroutines

Scheduler

Actors

Examples:

result := self foo // synchronous

futureResult := self futureSend(foo) // async, immediately returns a Future

self asyncSend(foo) // async, immediately returns nil

When an object receives an asynchronous message it puts the message in its queue and, if it doesn't already have one, starts a coroutine to process the messages in its queue. Queued messages are processed sequentially in a first-in-first-out order. Control can be yielded to other coroutines by calling "yield". Example:

obj1 := Object clone

obj1 test := method(for(n, 1, 3, n print; yield))

obj2 := obj1 clone

obj1 asyncSend(test); obj2 asyncSend(test)

while(Scheduler yieldingCoros size > 1, yield)

This would print "112233". Here's a more real world example:

HttpServer handleRequest := method(aSocket,

    HttpRequestHandler clone asyncSend(handleRequest(aSocket))

)

Futures

Auto Deadlock Detection

An advantage of using futures is that when a future requires a wait, it will check to see if pausing to wait for the result would cause a deadlock and if so, avoid the deadlock and raise an exception. It performs this check by traversing the list of connected futures.

Futures and the Command Line Interface

The command line will attempt to print the result of expressions evaluated in it, so if the result is a Future, it will attempt to print it and this will wait on the result of Future. Example:

Io> q := method(wait(1))

Io> futureSend(q)

[1-second delay]

==> nil

To avoid this, just make sure the Future isn't the result. Example:

Io> futureSend(q); nil

[no delay]

==> nil

Yield

Pause and Resume

It's also possible to pause and resume an object. See the concurrency methods of the Object primitive for details and related methods.

Exceptions

Raise

Exception raise("generic foo exception")

Try and Catch

e := try(<doMessage>)

To catch a particular exception, the Exception catch() method can be used. Example:

e := try(

    // ...

) 

e catch(Exception,

    writeln(e coroutine backTraceString)

)

The first argument to catch indicates which types of exceptions will be caught. catch() returns the exception if it doesn't match and nil if it does.

Pass

e := try(

    // ...

) 

e catch(Error,

    // ...

) catch(Exception,

    // ...

) pass

Custom Exceptions

MyErrorType := Error clone

Primitives

Object

The ? Operator

Sometimes it's desirable to conditionally call a method only if it exists (to avoid raising an exception). Example:

if(obj getSlot("foo"), obj foo)

Putting a "?" before a message has the same effect:

obj ?foo

List

Create an empty list:

a := List clone

Create a list of arbitrary objects using the list() method:

a := list(33, "a")

Append an item:

a append("b")

==> list(33, "a", "b")

Get the list size:

a size

==> 3

Get the item at a given index (List indexes begin at zero):

a at(1)

==> "a"

Note: List indexes begin at zero and nil is returned if the accessed index doesn't exist.

Set the item at a given index:

a atPut(2, "foo")

==> list(33, "a", "foo", "b")

a atPut(6, "Fred")

==> Exception: index out of bounds

Remove an item at a given index:

a remove("foo")

==> list(33, "a", "b")

Inserting an item at a given index:

a atInsert(2, "foo")

==> list(33, "a", "foo", "56")

foreach

The foreach, map and select methods can be used in three forms:

Io> a := list(65, 21, 122)

In the first form, the first argument is used as an index variable, the second as a value variable and the 3rd as the expression to evaluate for each value.

Io> a foreach(i, v, write(i, ":", v, ", "))

==> 0:65, 1:21, 2:122,

The second form removes the index argument:

Io> a foreach(v, v println)

==> 65

21

122

The third form removes the value argument and simply sends the expression as a message to each value:

Io> a foreach(println)

==> 65

21

122

map and select

Io's map and select (known as filter in some other languages) methods allow arbitrary expressions as the map/select predicates.

Io> numbers := list(1, 2, 3, 4, 5, 6)

Io> numbers select(isOdd)

==> list(1, 3, 5)

Io> numbers select(x, x isOdd)

==> list(1, 3, 5)

Io> numbers select(i, x, x isOdd)

==> list(1, 3, 5)

Io> numbers map(x, x*2)

==> list(2, 4, 6, 8, 10, 12)

Io> numbers map(i, x, x+i)

==> list(1, 3, 5, 7, 9, 11)

Io> numbers map(*3)

==> list(3, 6, 9, 12, 15, 18)

The map and select methods return new lists. To do the same operations in-place, you can use selectInPlace() and mapInPlace() methods.

Sequence

"abc" size

==> 3

Checking if a string contains a substring:

"apples" containsSeq("ppl")

==> true

Getting the character (byte) at position N:

"Kavi" at(1)

==> 97

Slicing:

"Kirikuro" slice(0, 2)

==> "Ki"

"Kirikuro" slice(-2)  # NOT: slice(-2, 0)!

==> "ro"

Io> "Kirikuro" slice(0, -2)

# "Kiriku"

Stripping whitespace:

"  abc  " asMutable strip

==> "abc"

"  abc  " asMutable lstrip

==> "abc  "

"  abc  " asMutable rstrip

==> "  abc"

Converting to upper/lowercase:

"Kavi" asUppercase

==> "KAVI"

"Kavi" asLowercase

==> "kavi"

Splitting a string:

"the quick brown fox" split

==> list("the", "quick", "brown", "fox")

Splitting by others character is possible as well.

"a few good men" split("e")

==> list("a f", "w good m", "n")

Converting to number:

"13" asNumber

==> 13

"a13" asNumber

==> nil

String interpolation:

name := "Fred"

==> Fred

"My name is #{name}" interpolate

==> My name is Fred
 

Interpolate will eval anything with #{} as Io code in the local context. The code may include loops or anything else but needs to return an object that responds to asString.

Ranges

The Range protocol

Each object that can be used in Ranges needs to implement a "nextInSequence" method which takes a single optional argument (the number of items to skip in the sequence of objects), and return the next item after that skip value. The default skip value is 1. The skip value of 0 is undefined. An example:

Number nextInSequence := method(skipVal,

    if(skipVal isNil, skipVal = 1)

    self + skipVal

)

With this method on Number (it's already there in the standard libraries), you can then use Numbers in Ranges, as demonstrated below:

1 to(5) foreach(v, v println)

The above will print 1 through 5, each on its own line.

File

f := File with("foo.txt)

f remove

f openForUpdating

f write("hello world!")

f close

Directory

dir := Directory with("/Users/steve/")

Get a list of file objects for all the files in a directory:

files := dir files

==> list(File_0x820c40, File_0x820c40, ...)

Get a list of both the file and directory objects in a directory:

items := Directory items

==> list(Directory_0x8446b0, File_0x820c40, ...)

items at(4) name

==> DarkSide-0.0.1 # a directory name

Setting a Directory object to a certain directory and using it:

root := Directory clone setPath("c:/")

==> Directory_0x8637b8

root fileNames

==> list("AUTOEXEC.BAT", "boot.ini", "CONFIG.SYS", ...)

Testing for existence:

Directory clone setPath("q:/") exists

==> false

Getthing the current working directory:

Directory currentWorkingDirectory

==> "/cygdrive/c/lang/IoFull-Cygwin-2006-04-20"

Date

d := Date clone

Setting it to the current date/time:

d now

Getting the date/time as a number, in seconds:

Date now asNumber

==> 1147198509.417114

Date now asNumber

==> 1147198512.33313

Getting individual parts of a Date object:

d := Date now

==> 2006-05-09 21:53:03 EST

d

==> 2006-05-09 21:53:03 EST

d year

==> 2006

d month

==> 5

d day

==> 9

d hour

==> 21

d minute

==> 53

d second

==> 3.747125

Find how long it takes to execute some code:

Date cpuSecondsToRun(100000 repeat(1+1))

==> 0.02

Networking

Creating a URL object:

url := URL with("http://example.com/")

Fetching an URL:

data := url fetch

Streaming a URL to a file:

url streamTo(File with("out.txt"))

A simple whois client:

whois := method(host,

    socket := Socket clone \

		setHostName("rs.internic.net") setPort(43)

    socket connect streamWrite(host, "\n")

    while(socket streamReadNextChunk, nil)

    return socket readBuffer

)

A minimal web server:

WebRequest := Object clone do(

    handleSocket := method(aSocket,

        aSocket streamReadNextChunk

        request := aSocket readBuffer \

			betweenSeq("GET ", " HTTP")

        f := File with(request)

        if(f exists,

			f streamTo(aSocket)

		,

			aSocket streamWrite("not found")

		)

        aSocket close

    )

)

WebServer := Server clone do(

    setPort(8000)

    handleSocket := method(aSocket,

        WebRequest clone asyncSend(handleSocket(aSocket))

    )

)

WebServer start

XML

SGML // reference this to load the SGML addon

xml := URL with("http://www.yahoo.com/") fetch asXML

links := xml elementsWithName("a") map(attributes at("href"))

Vector

Vector := Sequence clone setItemType("float32")

The Sequence primitive supports SIMD acceleration on a number of float32 operations. Currently these include add, subtract, multiple and divide but in the future can be extended to support most math, logic and string manipulation related operations. Here's a small example:

iters := 1000

size := 1024

ops := iters * size

v1 := Vector clone setSize(size) rangeFill

v2 := Vector clone setSize(size) rangeFill

dt := Date secondsToRun(

    iters repeat(v1 *= v2)

)

writeln((ops/(dt*1000000000)) asString(1, 3), " GFLOPS")

Which when run on 2Ghz Mac Laptop, outputs:

1.255 GFLOPS

A similar bit of C code (without SIMD acceleration) outputs:

0.479 GFLOPS

So for this example, Io is about three times faster than plain C.

Unicode

Sequences

uint8, uint16, uint32, uint64

int8, int16, int32, int64

float32, float64

Encodings

number, ascii, ucs2, ucs4, utf8

UCS-2 and UCS-4 are the fixed character width versions of UTF-16 and UTF-32, respectively. A String is just a Sequence with a text encoding, a Symbol is an immutable String and a Vector is a Sequence with a number encoding.

UTF encodings are assumed to be big endian.

Except for input and output, all strings should be kept in a fixed character width encoding. This design allows for a simpler implementation, code sharing between vector and string ops, fast index-based access, and SIMD acceleration of Sequence operations. All Sequence methods will do automatic type conversions as needed.

Source Code

Io> "hello" encoding

==> ascii

Io> "π" encoding

==> ucs2

Io> "∞" encoding

==> ucs2

We can also inspect the internal representation:

Io> "π" itemType

==> uint16

Io> "π" itemSize

==> 2

Conversion

asUTF8

asUCS2

asUCS4

Embedding

Conventions

Structures

Member names are words that begin with a lower case character with successive words each having their first character upper cased. Acronyms are capitalized. Structure names are words with their first character capitalized. Example:

typdef struct

{

    char *firstName;

    char *lastName;

    char *address;

} Person;

Functions

Function names begin with the name of structure they operate on followed by an underscore and the method name. Each structure has a new and free function.

Example:

List *List_new(void);

void List_free(List *self);

All methods (except new) have the structure (the "object") as the first argument the variable is named "self". Method names are in keyword format. That is, for each argument, the method name has a description followed by an underscore. The casing of the descriptions follow that of structure member names.

Examples:

int List_count(List *self); // no argument

void List_add_(List *self, void *item); // one argument

void Dictionary_key_value_(Dictionary *self,

	char *key, char *value);

File Names

Each structure has its own separate .h and .c files. The names of the files are the same as the name of the structure. These files contain all the functions(methods) that operate on the given structure.

IoState

Multiple states

Io is multi-state, meaning that it is designed to support multiple state instances within the same process. These instances are isolated and share no memory so they can be safely accessed simultaneously by different os threads, though a given state should only be accessed by one os thread at a time.

Creating a state

Here's a simple example of creating a state, evaluating a string in it, and freeing the state:

#include "IoState.h"

int main(int argc, const char *argv[])

{

    IoState *self = IoState_new();

    IoState_init(self);

    IoState_doCString_(self, "writeln(\"hello world!\"");

    IoState_free(self);

    return 0;

}

Values

IoObject *v = IoState_doCString_(self, someString);

char *name = IoObject_name(v);

printf("return type is a ‘%s', name);

IoObject_print(v);

Checking value types

There are some macro short cuts to help with quick type checks:

if (ISNUMBER(v))

{

    printf("result is the number %f", IoNumber_asFloat(v));

}

else if(ISSEQ(v))

{

    printf("result is the string %s", IoSeq_asCString(v));

}

else if(ISLIST(v))

{

    printf("result is a list with %i elements",

		IoList_rawSize(v));

}

Note that return values are always proper Io objects (as all values are objects in Io). You can find the C level methods (functions like IoList_rawSize()) for these objects in the header files in the folder Io/libs/iovm/source.

Bindings

Appendix

Grammar

messages

expression ::= { message | sctpad }

message ::= [wcpad] symbol [scpad] [arguments]

arguments ::= Open [argument [ { Comma argument } ]] Close

argument ::= [wcpad] expression [wcpad]

symbols

symbol ::= Identifier | number | Operator | quote

Identifier ::= { letter | digit | "_" }

Operator ::= { ":" | "." | "'" | "~" | "!" | "@" | "$" |

"%" | "^" | "&" | "*" | "-" | "+" | "/" | "=" | "{" | "}" |

"[" | "]" | "|" | "\" | "<" | ">" | "?" }

quotes

quote ::= MonoQuote | TriQuote

MonoQuote ::= """ [ "\"" | not(""")] """

TriQuote ::= """"" [ not(""""")] """""

spans

Terminator ::= { [separator] ";" | "\n" | "\r" [separator] }

separator ::= { " " | "\f" | "\t" | "\v" }

whitespace ::= { " " | "\f" | "\r" | "\t" | "\v" | "\n" }

sctpad ::= { separator | Comment | Terminator }

scpad ::= { separator | Comment }

wcpad ::= { whitespace | Comment }

comments

Comment ::= slashStarComment | slashSlashComment | poundComment

slashStarComment ::= "/*" [not("*/")] "*/"

slashSlashComment ::= "//" [not("\n")] "\n"

poundComment ::= "#" [not("\n")] "\n"

numbers

number ::= HexNumber | Decimal

HexNumber ::= "0" anyCase("x") { [ digit | hexLetter ] }

hexLetter ::= "a" | "b" | "c" | "d" | "e" | "f"

Decimal ::= digits | "." digits |

	digits "." digits ["e" [-] digits]

characters

Comma ::= ","

Open ::= "(" | "[" | "{"

Close ::= ")" | "]" | "}"

letter ::= "a" ... "z" | "A" ... "Z"

digit ::= "0" ... "9"

digits ::= { digit }

The uppercase words above designate elements the lexer treats as tokens.

Credits

References

License

Redistribution and use of this document with or without modification, are permitted provided that the copies reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

This documentation is provided "as is" and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall the authors be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this documentation, even if advised of the possibility of such damage.