feat: replace IO class with System class and remove separate IO module

- Delete wren_io.c, wren_io.h, and io.wren source files
- Remove multi-arity print overloads and IO.read/IO.time methods
- Add System class with print, printAll, write, writeAll methods to core.wren
- Update all documentation examples and README to use System.print instead of IO.print

doc/site/classes.markdown

@@ -25,7 +25,7 @@ To let our unicorn do stuff, we need to give it methods.
     :::dart
     class Unicorn {
       prance() {
-        IO.print("The unicorn prances in a fancy manner!")
+        System.print("The unicorn prances in a fancy manner!")
       }
     }
 
@@ -35,7 +35,7 @@ parameters, put their names inside the parentheses:
     :::dart
     class Unicorn {
       prance(where, when) {
-        IO.print("The unicorn prances in " + where + " at " + when)
+        System.print("The unicorn prances in " + where + " at " + when)
       }
     }
 
@@ -49,15 +49,15 @@ fine:
     :::dart
     class Unicorn {
       prance() {
-        IO.print("The unicorn prances in a fancy manner!")
+        System.print("The unicorn prances in a fancy manner!")
       }
 
       prance(where) {
-        IO.print("The unicorn prances in " + where)
+        System.print("The unicorn prances in " + where)
       }
 
       prance(where, when) {
-        IO.print("The unicorn prances in " + where + " at " + when)
+        System.print("The unicorn prances in " + where + " at " + when)
       }
     }
 
@@ -83,7 +83,7 @@ Many methods on a class exist to expose or compute some property of the object.
 For example:
 
     :::dart
-    IO.print("string".count) // "6".
+    System.print("string".count) // "6".
 
 These *getters* are just another kind of method—one without a parameter
 list. You can define them like so:
@@ -152,12 +152,12 @@ You can define operators in your class like so:
     class Unicorn {
       // Infix:
       +(other) {
-        IO.print("Adding to a unicorn?")
+        System.print("Adding to a unicorn?")
       }
 
       // Prefix:
       ! {
-        IO.print("Negating a unicorn?!")
+        System.print("Negating a unicorn?!")
       }
     }
 
@@ -191,7 +191,7 @@ like so:
     :::dart
     class Unicorn {
       construct new(name, color) {
-        IO.print("My name is " + name + " and I am " + color + ".")
+        System.print("My name is " + name + " and I am " + color + ".")
       }
     }
 
@@ -210,7 +210,7 @@ and each can clarify how it creates the instance:
     :::dart
     class Unicorn {
       construct brown(name) {
-        IO.print("My name is " + name + " and I am brown.")
+        System.print("My name is " + name + " and I am brown.")
       }
     }
 
@@ -326,13 +326,13 @@ not the instance. They can be used in *both* instance and static methods.
 Just like instance fields, static fields are initially `null`:
 
     :::dart
-    IO.print(Foo.bar) // null.
+    System.print(Foo.bar) // null.
 
 They can be used from static methods:
 
     :::dart
     Foo.set("foo")
-    IO.print(Foo.bar) // foo.
+    System.print(Foo.bar) // foo.
 
 And also instance methods. When you do so, there is still only one static field
 shared among all instances of the class:
@@ -342,7 +342,7 @@ shared among all instances of the class:
     var foo2 = Foo.new()
 
     foo1.setFromInstance("updated")
-    IO.print(foo2.baz) // updated.
+    System.print(foo2.baz) // updated.
 
 ## Inheritance
 
@@ -381,7 +381,7 @@ This also means constructors are not inherited:
     :::dart
     class Unicorn {
       this new(name) {
-        IO.print("My name is " + name + ".")
+        System.print("My name is " + name + ".")
       }
     }
 
@@ -398,7 +398,7 @@ This means you can do `super` calls inside a constructor:
     :::dart
     class Unicorn {
       this new(name) {
-        IO.print("My name is " + name + ".")
+        System.print("My name is " + name + ".")
       }
     }
 

doc/site/control-flow.markdown

@@ -31,7 +31,7 @@ The simplest branching statement, `if` lets you conditionally skip a chunk of
 code. It looks like this:
 
     :::dart
-    if (ready) IO.print("go!")
+    if (ready) System.print("go!")
 
 That evaluates the parenthesized expression after `if`. If it's true, then the
 statement after the condition is evaluated. Otherwise it is skipped. Instead of
@@ -39,23 +39,23 @@ a statement, you can have a [block](syntax.html#blocks):
 
     :::dart
     if (ready) {
-      IO.print("getSet")
-      IO.print("go!")
+      System.print("getSet")
+      System.print("go!")
     }
 
 You may also provide an `else` branch. It will be executed if the condition is
 false:
 
     :::dart
-    if (ready) IO.print("go!") else IO.print("not ready!")
+    if (ready) System.print("go!") else System.print("not ready!")
 
 And, of course, it can take a block too:
 
     :::dart
     if (ready) {
-      IO.print("go!")
+      System.print("go!")
     } else {
-      IO.print("not ready!")
+      System.print("not ready!")
     }
 
 ## While statements
@@ -100,7 +100,7 @@ That's what `for` is for. It looks like this:
 
     :::dart
     for (beatle in ["george", "john", "paul", "ringo"]) {
-      IO.print(beatle)
+      System.print(beatle)
     }
 
 A `for` loop has three components:
@@ -124,7 +124,7 @@ keyword all by itself. That will immediately exit out of the nearest enclosing
 
     :::dart
     for (i in [1, 2, 3, 4]) {
-      IO.print(i)
+      System.print(i)
       if (i == 3) break
     }
 
@@ -138,7 +138,7 @@ sequence of numbers, or loop a number of times. For that, you can create a
 
     :::dart
     for (i in 1..100) {
-      IO.print(i)
+      System.print(i)
     }
 
 This loops over the numbers from 1 to 100, including 100 itself. If you want to
@@ -146,7 +146,7 @@ leave off the last value, use three dots instead of two:
 
     :::dart
     for (i in 1...100) {
-      IO.print(i)
+      System.print(i)
     }
 
 This looks like some special "range" syntax in the `for` loop, but it's
@@ -168,7 +168,7 @@ When you write a loop like this:
 
     :::dart
     for (i in 1..100) {
-      IO.print(i)
+      System.print(i)
     }
 
 Wren sees it something like this:
@@ -178,7 +178,7 @@ Wren sees it something like this:
     var seq_ = 1..100
     while (iter_ = seq_.iterate(iter_)) {
       var i = seq_.iteratorValue(iter_)
-      IO.print(i)
+      System.print(i)
     }
 
 First, Wren evaluates the sequence expression and stores it in a hidden

doc/site/core/bool.markdown

@@ -9,10 +9,9 @@ Boolean values. There are two instances, `true` and `false`.
 
 Returns the logical complement of the value.
 
-    > !true
-    false
-    > !false
-    true
+    :::dart
+    System.print(!true) // "false".
+    System.print(!false) // "true".
 
 ### toString
 

doc/site/core/class.markdown

@@ -15,14 +15,14 @@ The superclass of this class.
     class Crustacean {}
     class Crab is Crustacean {}
 
-    IO.print(Crab.supertype)        // "Crustacean"
+    System.print(Crab.supertype) // "Crustacean".
 
 A class with no explicit superclass implicitly inherits Object:
 
     :::dart
-    IO.print(Crustacean.supertype)  // "Object"
+    System.print(Crustacean.supertype) // "Object".
 
 Object forms the root of the class hierarchy and has no supertype:
 
     :::dart
-    IO.print(Object.supertype)  // "null"
+    System.print(Object.supertype) // "null".

doc/site/core/fiber.markdown

@@ -10,7 +10,7 @@ fiber is run. Does not immediately start running the fiber.
 
     :::dart
     var fiber = Fiber.new {
-      IO.print("I won't get printed")
+      System.print("I won't get printed")
     }
 
 ## Static Methods
@@ -34,14 +34,14 @@ here means the last fiber that was started using `call` and not `run`.
 
     :::dart
     var fiber = Fiber.new {
-      IO.print("Before yield")
+      System.print("Before yield")
       Fiber.yield()
-      IO.print("After yield")
+      System.print("After yield")
     }
 
-    fiber.call()            // "Before yield"
-    IO.print("After call")  // "After call"
-    fiber.call()            // "After yield"
+    fiber.call()                // "Before yield"
+    System.print("After call")  // "After call"
+    fiber.call()                // "After yield"
 
 When resumed, the parent fiber's `call()` method returns `null`.
 
@@ -50,7 +50,7 @@ If a yielded fiber is resumed by calling `call()` or `run()` with an argument,
 
     :::dart
     var fiber = Fiber.new {
-      IO.print(Fiber.yield()) // "value"
+      System.print(Fiber.yield()) // "value"
     }
 
     fiber.call()        // Run until the first yield.
@@ -65,7 +65,7 @@ later.
 
     :::dart
     Fiber.yield()
-    IO.print("this does not get reached")
+    System.print("this does not get reached")
 
 ### Fiber.**yield**(value)
 
@@ -77,7 +77,7 @@ Similar to `Fiber.yield` but provides a value to return to the parent fiber's
       Fiber.yield("value")
     }
 
-    IO.print(fiber.call()) // "value"
+    System.print(fiber.call()) // "value"
 
 ## Methods
 
@@ -87,9 +87,9 @@ Starts or resumes the fiber if it is in a paused state.
 
     :::dart
     var fiber = Fiber.new {
-      IO.print("Fiber called")
+      System.print("Fiber called")
       Fiber.yield()
-      IO.print("Fiber called again")
+      System.print("Fiber called again")
     }
 
     fiber.call() // Start it.
@@ -103,7 +103,7 @@ If the called fiber is resuming from a yield, the `yield()` method returns
 
     :::dart
     var fiber = Fiber.new {
-      IO.print(Fiber.yield())
+      System.print(Fiber.yield())
     }
 
     fiber.call()
@@ -116,7 +116,7 @@ Invokes the fiber or resumes the fiber if it is in a paused state and sets
 
     :::dart
     var fiber = Fiber.new {
-      IO.print(Fiber.yield())
+      System.print(Fiber.yield())
     }
 
     fiber.call()

doc/site/core/fn.markdown

@@ -13,7 +13,7 @@ argument](../functions.html#block-arguments) to some other method.
 
     :::dart
     var fn = Fn.new {
-      IO.print("The body")
+      System.print("The body")
     }
 
 It is a runtime error if `function` is not a function.
@@ -25,8 +25,8 @@ It is a runtime error if `function` is not a function.
 The number of arguments the function requires.
 
     :::dart
-    IO.print(Fn.new {}.arity)             // 0.
-    IO.print(Fn.new {|a, b, c| a }.arity) // 3.
+    System.print(Fn.new {}.arity)             // 0.
+    System.print(Fn.new {|a, b, c| a }.arity) // 3.
 
 ### **call**(args...)
 
@@ -34,7 +34,7 @@ Invokes the function with the given arguments.
 
     :::dart
     var fn = Fn.new { |arg|
-      IO.print(arg)
+      System.print(arg)
     }
 
     fn.call("Hello world") // Prints "Hello world".

doc/site/core/index.markdown

@@ -20,6 +20,6 @@ All Wren source files automatically have access to the following classes:
 * [Range](range.html)
 * [Sequence](sequence.html)
 * [String](string.html)
-* [IO](io.html)
+* [System](system.html)
 
 [embedding]: ../embedding-api.html

doc/site/core/io.markdown

@@ -1,60 +0,0 @@
-^title IO Class
-^category core
-
-The IO class can be used to read and write to and from the console.
-
-## Static Methods
-
-### IO.**print**(objects...)
-
-Prints a series of objects to the console followed by a newline. Each object is
-converted to a string by calling `toString` on it. This is overloaded to
-support up to 16 objects. To pass more, use `printAll()`.
-
-  > IO.print("I like bananas")
-  I like bananas
-  > IO.print("Oranges", 10)
-  Oranges10
-
-### IO.**printAll**(sequence)
-
-Iterates over [sequence] and prints each element, then prints a single newline
-at the end. Each element is converted to a string by calling `toString` on it.
-
-  > IO.printAll([1, [2, 3], 4])
-  1[2, 3]4
-
-### IO.**write**(object)
-
-Prints a single value to the console, but does not print a newline character
-afterwards. Converts the value to a string by calling `toString` on it.
-
-  > IO.write(4 + 5)
-  9>
-
-In the above example, the result of `4 + 5` is printed, and then the prompt is
-printed on the same line because no newline character was printed afterwards.
-
-### IO.**read**()
-
-Reads in a line of text from stdin. Note that the returned text includes the
-trailing newline.
-
-  > var name = IO.read()
-  John
-  > IO.print("Hello " + name + "!")
-  Hello John
-  !
-  >
-
-### IO.**read**(prompt)
-
-Displays `prompt` then reads in a line of text from stdin. Note that the
-returned text includes the trailing newline.
-
-  > var name = IO.read("Enter your name: ")
-  Enter your name: John
-  > IO.print("Hello " + name + "!")
-  Hello John
-  !
-  >

doc/site/core/list.markdown

@@ -26,14 +26,14 @@ Inserts the `item` at `index` in the list.
     :::dart
     var list = ["a", "b", "c", "d"]
     list.insert(1, "e")
-    IO.print(list) // "[a, e, b, c, d]"
+    System.print(list) // "[a, e, b, c, d]".
 
 The `index` may be one past the last index in the list to append an element.
 
     :::dart
     var list = ["a", "b", "c"]
     list.insert(3, "d")
-    IO.print(list) // "[a, b, c, d]"
+    System.print(list) // "[a, b, c, d]".
 
 If `index` is negative, it counts backwards from the end of the list. It bases this on the length of the list *after* inserted the element, so that `-1` will append the element, not insert it before the last element.
 
@@ -41,12 +41,12 @@ If `index` is negative, it counts backwards from the end of the list. It bases t
     var list = ["a", "b"]
     list.insert(-1, "d")
     list.insert(-2, "c")
-    IO.print(list) // "[a, b, c, d]"
+    System.print(list) // "[a, b, c, d]".
 
 Returns the inserted item.
 
     :::dart
-    IO.print(["a", "c"].insert(1, "b")) // "b".
+    System.print(["a", "c"].insert(1, "b")) // "b".
 
 It is a runtime error if the index is not an integer or is out of bounds.
 
@@ -64,11 +64,11 @@ are shifted up to fill in where the removed element was.
     :::dart
     var list = ["a", "b", "c", "d"]
     list.removeAt(1)
-    IO.print(list) // "[a, c, d]".
+    System.print(list) // "[a, c, d]".
 
 Returns the removed item.
 
-    IO.print(["a", "b", "c"].removeAt(1)) // "b".
+    System.print(["a", "b", "c"].removeAt(1)) // "b".
 
 It is a runtime error if the index is not an integer or is out of bounds.
 
@@ -79,7 +79,7 @@ the end of the list where `-1` is the last element.
 
     :::dart
     var list = ["a", "b", "c"]
-    IO.print(list[1]) // "b".
+    System.print(list[1]) // "b".
 
 It is a runtime error if the index is not an integer or is out of bounds.
 
@@ -91,6 +91,6 @@ backwards from the end of the list where `-1` is the last element.
     :::dart
     var list = ["a", "b", "c"]
     list[1] = "new"
-    IO.print(list) // "[a, new, c]".
+    System.print(list) // "[a, new, c]".
 
 It is a runtime error if the index is not an integer or is out of bounds.

doc/site/core/map.markdown

@@ -50,8 +50,8 @@ map, returns `null`.
 
     :::dart
     var map = {"george": "harrison", "ringo": "starr"}
-    IO.print(map["ringo"]) // "starr".
-    IO.print(map["pete"])  // "null".
+    System.print(map["ringo"]) // "starr".
+    System.print(map["pete"])  // "null".
 
 ### **[**key**]=**(value) operator
 

doc/site/core/null.markdown

@@ -7,5 +7,5 @@
 
 Returns `true`, since `null` is considered [false](../control-flow.html#truth).
 
-    > !null
-    true
+    :::dart
+    System.print(!null) // "true".

doc/site/core/num.markdown

@@ -132,9 +132,9 @@ from the beginning number to the ending number.
 
     :::dart
     var range = 1.2..3.4
-    IO.print(range.min)         // 1.2
-    IO.print(range.max)         // 3.4
-    IO.print(range.isInclusive) // true
+    System.print(range.min)         // 1.2
+    System.print(range.max)         // 3.4
+    System.print(range.isInclusive) // true
 
 ### **...**(other) operator
 
@@ -143,6 +143,6 @@ from the beginning number to the ending number not including the ending number.
 
     :::dart
     var range = 1.2...3.4
-    IO.print(range.min)         // 1.2
-    IO.print(range.max)         // 3.4
-    IO.print(range.isInclusive) // false
+    System.print(range.min)         // 1.2
+    System.print(range.max)         // 3.4
+    System.print(range.isInclusive) // false

doc/site/core/sequence.markdown

@@ -59,7 +59,7 @@ and counting the number of times the returned value evaluates to `true`.
 Iterates over the sequence, passing each element to the given `function`.
 
     :::dart
-    ["one", "two", "three"].each {|word| IO.print(word) }
+    ["one", "two", "three"].each {|word| System.print(word) }
 
 ### **isEmpty**
 
@@ -88,7 +88,7 @@ original sequence while it is iterated.
     :::dart
     var doubles = [1, 2, 3].map {|n| n * 2 }
     for (n in doubles) {
-      IO.print(n) // "2", "4", "6".
+      System.print(n) // "2", "4", "6".
     }
 
 The returned sequence is *lazy*. It only applies the mapping when you iterate
@@ -105,7 +105,7 @@ To force eager evaluation, just call `.toList` on the result.
     var numbers = [1, 2, 3]
     var doubles = numbers.map {|n| n * 2 }.toList
     numbers.add(4)
-    IO.print(doubles) // [2, 4, 6].
+    System.print(doubles) // [2, 4, 6].
 
 ### **reduce**(function)
 
@@ -142,7 +142,7 @@ function `predicate`. If it returns `false`, the element is skipped.
     :::dart
     var odds = (1..10).where {|n| n % 2 == 1 }
     for (n in odds) {
-      IO.print(n) // "1", "3", "5", "7", "9".
+      System.print(n) // "1", "3", "5", "7", "9".
     }
 
 The returned sequence is *lazy*. It only applies the filtering when you iterate
@@ -160,4 +160,4 @@ To force eager evaluation, just call `.toList` on the result.
     var numbers = [1, 2, 3, 4, 5, 6]
     var odds = numbers.where {|n| n % 2 == 1 }.toList
     numbers.add(7)
-    IO.print(odds) // [1, 3, 5].
+    System.print(odds) // [1, 3, 5].

doc/site/core/string.markdown

@@ -37,7 +37,7 @@ on strings *return* byte indexes too. So, for example, this does what you want:
     :::dart
     var metalBand = "Fäcëhämmër"
     var hPosition = metalBand.indexOf("h")
-    IO.print(metalBand[hPosition]) // "h"
+    System.print(metalBand[hPosition]) // "h"
 
 If you want to work with a string as a sequence numeric code points, call the
 `codePoints` getter. It returns a [Sequence](sequence.html) that decodes UTF-8
@@ -68,7 +68,7 @@ methods, the returned object also has a subscript operator that can be used to
 directly index bytes.
 
     :::dart
-    IO.print("hello".bytes[1]) // 101, for "e".
+    System.print("hello".bytes[1]) // 101, for "e".
 
 The `count` method on the returned sequence returns the number of bytes in the
 string. Unlike `count` on the string itself, it does not have to iterate over
@@ -83,15 +83,15 @@ single-character strings, this returns the numeric code point values.
 
     :::dart
     var string = "(ᵔᴥᵔ)"
-    IO.print(string.codePoints[0]) // 40, for "(".
-    IO.print(string.codePoints[4]) // 7461, for "ᴥ".
+    System.print(string.codePoints[0]) // 40, for "(".
+    System.print(string.codePoints[4]) // 7461, for "ᴥ".
 
 If the byte at `index` does not begin a valid UTF-8 sequence, or the end of the
 string is reached before the sequence is complete, returns `-1`.
 
     :::dart
     var string = "(ᵔᴥᵔ)"
-    IO.print(string.codePoints[2]) // -1, in the middle of "ᵔ".
+    System.print(string.codePoints[2]) // -1, in the middle of "ᵔ".
 
 ### **contains**(other)
 
@@ -132,7 +132,7 @@ for iterating over the *code points* in the string:
       codePoints.add(c)
     }
 
-    IO.print(codePoints) // ["(", "ᵔ", "ᴥ", "ᵔ", ")"].
+    System.print(codePoints) // ["(", "ᵔ", "ᴥ", "ᵔ", ")"].
 
 If the string contains any bytes that are not valid UTF-8, this iterates over
 those too, one byte at a time.
@@ -162,7 +162,7 @@ Check if the string is not equal to `other`.
 Returns a string containing the code point starting at byte `index`.
 
     :::dart
-    IO.print("ʕ•ᴥ•ʔ"[5]) // "ᴥ".
+    System.print("ʕ•ᴥ•ʔ"[5]) // "ᴥ".
 
 Since `ʕ` is two bytes in UTF-8 and `•` is three, the fifth byte points to the
 bear's nose.
@@ -171,7 +171,7 @@ If `index` points into the middle of a UTF-8 sequence or at otherwise invalid
 UTF-8, this returns a one-byte string containing the byte at that index:
 
     :::dart
-    IO.print("I ♥ NY"[3]) // One-byte string whose value is 153.
+    System.print("I ♥ NY"[3]) // One-byte string whose value is 153.
 
 It is a runtime error if `index` is greater than the number of bytes in the
 string.

doc/site/core/system.markdown

@@ -0,0 +1,43 @@
+^title System Class
+^category core
+
+The System class is a grab-bag of functionality exposed by the VM, mostly for
+use during development or debugging.
+
+## Static Methods
+
+### System.**print**()
+
+Prints a single newline to the console.
+
+### System.**print**(object)
+
+Prints [object] to the console followed by a newline. If not already a string,
+the object is converted to a string by calling `toString` on it.
+
+    :::dart
+    System.print("I like bananas") // Prints "I like bananas".
+
+### System.**printAll**(sequence)
+
+Iterates over [sequence] and prints each element, then prints a single newline
+at the end. Each element is converted to a string by calling `toString` on it.
+
+    :::dart
+    System.printAll([1, [2, 3], 4]) // Prints "1[2, 3]4".
+
+### System.**write**(object)
+
+Prints a single value to the console, but does not print a newline character
+afterwards. Converts the value to a string by calling `toString` on it.
+
+    :::dart
+    System.write(4 + 5) // Prints "9".
+
+In the above example, the result of `4 + 5` is printed, and then the prompt is
+printed on the same line because no newline character was printed afterwards.
+
+### System.**clock**
+
+Returns the number of seconds (including fractional seconds) since the program
+was started. This is usually used for benchmarking.

doc/site/embedding-api.markdown

@@ -70,7 +70,7 @@ You can tell the VM to execute a string of Wren source code like so:
     :::c
     WrenInterpretResult result = wrenInterpret(vm,
         "<where>",
-        "IO.print(\"Hi!\")");
+        "System.print(\"Hi!\")");
 
 The first string parameter is a "source path". It's just an arbitrary string that describes where the source code is from. It's what shows up in stack traces if a runtime error occurs in the code. It can be whatever you want as long as it's not `NULL`.
 

doc/site/error-handling.markdown

@@ -108,7 +108,7 @@ For example, if you run this program:
     }
 
     var error = fiber.try()
-    IO.print("Caught error: ", error)
+    System.print("Caught error: " + error)
 
 It prints:
 
@@ -120,7 +120,7 @@ usual. When a fiber has been aborted because of a runtime error, you can also
 get the error from the fiber object. Continuing the above example:
 
     :::dart
-    IO.print(fiber.error)
+    System.print(fiber.error)
 
 This also prints:
 

doc/site/expressions.markdown

@@ -29,7 +29,7 @@ Wren is object-oriented, so most code consists of method calls. Most of them
 look like so:
 
     :::dart
-    IO.print("hello")
+    System.print("hello")
     items.add("another")
     items.insert(1, "value")
 
@@ -61,7 +61,7 @@ argument](functions.html#block-arguments):
 
     :::dart
     blondie.callMeAt(867, 5309) {
-      IO.print("This is the body!")
+      System.print("This is the body!")
     }
 
 Semantically, all method calls work like so:
@@ -98,7 +98,7 @@ call:
     :::dart
     class Base {
       method {
-        IO.print("base method")
+        System.print("base method")
       }
     }
 
@@ -114,7 +114,7 @@ base class constructor:
     :::dart
     class Base {
       this new(arg) {
-        IO.print("base constructor got ", arg)
+        System.print("base constructor got " + arg)
       }
     }
 
@@ -218,16 +218,16 @@ A `&&` ("logical and") expression evaluates the left-hand argument. If it's
 and returns the right-hand argument.
 
     :::dart
-    IO.print(false && 1)  // false
-    IO.print(1 && 2)      // 2
+    System.print(false && 1)  // false
+    System.print(1 && 2)      // 2
 
 An `||` ("logical or") expression is reversed. If the left-hand argument is
 [true](control-flow.html#truth), it's returned, otherwise the right-hand
 argument is evaluated and returned:
 
     :::dart
-    IO.print(false || 1)  // 1
-    IO.print(1 || 2)      // 1
+    System.print(false || 1)  // 1
+    System.print(1 || 2)      // 1
 
 ## The conditional operator `?:`
 
@@ -236,7 +236,7 @@ the little "if statement in the form of an expression" you know and love from C
 and its brethren.
 
     :::dart
-    IO.print(1 != 2 ? "math is sane" : "math is not sane!")
+    System.print(1 != 2 ? "math is sane" : "math is not sane!")
 
 It takes a condition expression, followed by `?`, followed by a then
 expression, a `:`, then an else expression. Just like `if`, it evaluates the

doc/site/fibers.markdown

@@ -28,7 +28,7 @@ using the `Fiber` class's constructor:
 
     :::dart
     var fiber = Fiber.new {
-      IO.print("This runs in a separate fiber.")
+      System.print("This runs in a separate fiber.")
     }
 
 Creating a fiber does not immediately run it. It's just a first class bundle of
@@ -48,7 +48,7 @@ until it passes control to another fiber. If it reaches the end of its body,
 it's considered *done*:
 
     :::dart
-    var fiber = Fiber.new { IO.print("Hi") }
+    var fiber = Fiber.new { System.print("Hi") }
     fiber.isDone // false
     fiber.call()
     fiber.isDone // true
@@ -71,16 +71,16 @@ You can make a fiber yield by calling the static `yield()` method on `Fiber`:
 
     :::dart
     var fiber = Fiber.new {
-      IO.print("fiber 1")
+      System.print("fiber 1")
       Fiber.yield()
-      IO.print("fiber 2")
+      System.print("fiber 2")
     }
 
-    IO.print("main 1")
+    System.print("main 1")
     fiber.call()
-    IO.print("main 2")
+    System.print("main 2")
     fiber.call()
-    IO.print("main 3")
+    System.print("main 3")
 
 This program prints:
 
@@ -105,7 +105,7 @@ of the `yield()` call:
     :::dart
     var fiber = Fiber.new {
       var result = Fiber.yield()
-      IO.print(result)
+      System.print(result)
     }
 
     fiber.call("discarded")
@@ -124,7 +124,7 @@ invoke the fiber:
       Fiber.yield("sent")
     }
 
-    IO.print(fiber.call())
+    System.print(fiber.call())
 
 This also prints "sent".
 

doc/site/functions.markdown

@@ -22,7 +22,7 @@ a method. At its simplest, it looks like this:
 
     :::dart
     blondie.callMe {
-      IO.print("This is the body!")
+      System.print("This is the body!")
     }
 
 Here we're invoking the `callMe` method on `blondie`. We're passing one
@@ -44,7 +44,7 @@ the block just like a regular argument list. For example:
 
     :::dart
     blondie.callMeAt(867, 5309) {
-      IO.print("This is the body!")
+      System.print("This is the body!")
     }
 
 Of course, you don't *have* to use a block argument to pass a function to a
@@ -62,7 +62,7 @@ class's constructor:
 
     :::dart
     var someFn = Fn.new {
-      IO.print("Hi!")
+      System.print("Hi!")
     }
 
 As you can see it takes a block argument too! All the constructor does it
@@ -87,7 +87,7 @@ method is dynamically-dispatched like any other, so you can define your own
     :::dart
     class FakeFn {
       call() {
-        IO.print("I'm feeling functional!")
+        System.print("I'm feeling functional!")
       }
     }
 
@@ -102,7 +102,7 @@ of the body, like so:
 
     :::dart
     blondie.callMe {|first, last|
-      IO.print("Hi, " + first + " " + last + "!")
+      System.print("Hi, " + first + " " + last + "!")
     }
 
 Here we're passing a function to `greet` that takes two parameters, `first` and
@@ -157,6 +157,6 @@ to`i`:
 
     :::dart
     var counter = Counter.create
-    IO.print(counter.call()) // Prints "1".
-    IO.print(counter.call()) // Prints "2".
-    IO.print(counter.call()) // Prints "3".
+    System.print(counter.call()) // Prints "1".
+    System.print(counter.call()) // Prints "2".
+    System.print(counter.call()) // Prints "3".

doc/site/getting-started.markdown

@@ -49,12 +49,12 @@ interactive mode. You can type in a line of code, and it will immediately
 execute it. Here's something to try:
 
     :::dart
-    IO.print("Hello, world!")
+    System.print("Hello, world!")
 
 Or a little more exciting:
 
     :::dart
-    for (i in 1..10) IO.print("Counting up ", i)
+    for (i in 1..10) System.print("Counting up " + i.toString)
 
 You can exit the interpreter using good old Ctrl-C or Ctrl-D, or just throw
 your computer to the ground and storm off.
@@ -80,10 +80,10 @@ your favorite text editor and paste this into it:
           y0 = y1
           iter = iter + 1
         }
-        IO.write(" .-:;+=xX$& "[iter])
+        System.write(" .-:;+=xX$& "[iter])
       }
 
-      IO.print("")
+      System.print("")
     }
 
 Now run:

doc/site/index.markdown

@@ -6,11 +6,11 @@ Think Smalltalk in a Lua-sized package with a dash of Erlang and wrapped up in
 a familiar, modern [syntax][].
 
     :::dart
-    IO.print("Hello, world!")
+    System.print("Hello, world!")
 
     class Wren {
       flyTo(city) {
-        IO.print("Flying to ", city)
+        System.print("Flying to " + city)
       }
     }
 
@@ -18,7 +18,7 @@ a familiar, modern [syntax][].
       ["small", "clean", "fast"].each {|word| Fiber.yield(word) }
     }
 
-    while (!adjectives.isDone) IO.print(adjectives.call())
+    while (!adjectives.isDone) System.print(adjectives.call())
 
  *  **Wren is small.** The VM implementation is under [4,000 semicolons][src].
     You can skim the whole thing in an afternoon. It's *small*, but not

doc/site/lists.markdown

@@ -59,14 +59,14 @@ existing element in the list using the subscript setter:
 
     :::dart
     hirsute[1] = "muttonchops"
-    IO.print(hirsute[1]) // muttonchops.
+    System.print(hirsute[1]) // muttonchops.
 
 It's an error to set an element that's out of bounds. To grow a list, you can
 use `add` to append a single item to the end:
 
     :::dart
     hirsute.add("goatee")
-    IO.print(hirsute.count) // 4.
+    System.print(hirsute.count) // 4.
 
 You can insert a new element at a specific position using `insert`:
 
@@ -84,9 +84,9 @@ back. Doing so counts back from the size of the list *after* it's grown by one:
     :::dart
     var letters = ["a", "b", "c"]
     letters.insert(3, "d")   // OK: inserts at end.
-    IO.print(letters)        // ["a", "b", "c", "d"]
+    System.print(letters)        // ["a", "b", "c", "d"]
     letters.insert(-2, "e")  // Counts back from size after insert.
-    IO.print(letters)        // ["a", "b", "c", "e", "d"]
+    System.print(letters)        // ["a", "b", "c", "e", "d"]
 
 ## Removing elements
 
@@ -97,15 +97,15 @@ gap:
     :::dart
     var letters = ["a", "b", "c", "d"]
     letters.removeAt(1)
-    IO.print(letters) // ["a", "c", "d"]
+    System.print(letters) // ["a", "c", "d"]
 
 The `removeAt` method returns the removed item:
 
     :::dart
-    IO.print(letters.removeAt(1)) // "c"
+    System.print(letters.removeAt(1)) // "c"
 
 If you want to remove everything from the list, you can clear it:
 
     :::dart
     hirsute.clear()
-    IO.print(hirsute) // []
+    System.print(hirsute) // []

doc/site/maps.markdown

@@ -58,7 +58,7 @@ To find the value associated with some key, again you use your friend the
 subscript operator:
 
     :::dart
-    IO.print(capitals["Idaho"]) // "Boise".
+    System.print(capitals["Idaho"]) // "Boise".
 
 If the key is present, this returns its value. Otherwise, it returns `null`. Of
 course, `null` itself can also be used as a value, so seeing `null` here
@@ -69,15 +69,15 @@ To tell definitively if a key exists, you can call `containsKey()`:
     :::dart
     var belief = {"nihilism": null}
 
-    IO.print(belief["nihilism"]) // "null" though key exists.
-    IO.print(belief["solipsism"]) // Also "null".
-    IO.print(belief.containsKey("nihilism")) // "true".
-    IO.print(belief.containsKey("solipsism")) // "false".
+    System.print(belief["nihilism"]) // "null" though key exists.
+    System.print(belief["solipsism"]) // Also "null".
+    System.print(belief.containsKey("nihilism")) // "true".
+    System.print(belief.containsKey("solipsism")) // "false".
 
 You can see how many entries a map contains using `count`:
 
     :::dart
-    IO.print(capitals.count) // "3".
+    System.print(capitals.count) // "3".
 
 ## Removing entries
 
@@ -86,12 +86,12 @@ entry you want to delete:
 
     :::dart
     capitals.remove("Maine")
-    IO.print(capitals.containsKey("Maine")) // "false".
+    System.print(capitals.containsKey("Maine")) // "false".
 
 If the key was found, this returns the value that was associated with it:
 
     :::dart
-    IO.print(capitals.remove("Georgia")) // "Atlanta".
+    System.print(capitals.remove("Georgia")) // "Atlanta".
 
 If the key wasn't in the map to begin with, `remove()` just returns `null`.
 
@@ -100,7 +100,7 @@ can just call `clear()`:
 
     :::dart
     capitals.clear()
-    IO.print(capitals.count) // "0".
+    System.print(capitals.count) // "0".
 
 [lists]: lists.html
 
@@ -120,14 +120,14 @@ If you want to see all of the key-value pairs in a map, the easiest way is to
 iterate over the keys and use each to look up its value:
 
     :::dart
-    var stateBirds = {
+    var birds = {
       "Arizona": "Cactus wren",
       "Hawaii": "Nēnē",
       "Ohio": "Northern Cardinal"
     }
 
-    for (state in stateBirds.keys) {
-      IO.print("The state bird of ", state, " is ", stateBirds[state])
+    for (state in birds.keys) {
+      System.print("The state bird of " + state + " is " + birds[state])
     }
 
 This program will print the three states and their birds. However, the *order*

doc/site/modules.markdown

@@ -173,7 +173,7 @@ like:
     import "shared"
 
     // shared.wren
-    IO.print("Shared!")
+    System.print("Shared!")
 
 Here, "a" and "b" both want to use "shared". If "shared" defines some top-level
 state, we only want a single copy of that in memory. To handle this, a module's
@@ -211,14 +211,14 @@ For example:
     import "a"
 
     // a.wren
-    IO.print("start a")
+    System.print("start a")
     import "b"
-    IO.print("end a")
+    System.print("end a")
 
     // b.wren
-    IO.print("start b")
+    System.print("start b")
     import "a"
-    IO.print("end b")
+    System.print("end b")
 
 This program runs successfully and prints:
 

doc/site/syntax.markdown

@@ -54,15 +54,15 @@ Newlines (`\n`) are meaningful in Wren. They are used to separate statements:
 
     :::dart
     // Two statements:
-    IO.print("hi") // Newline.
-    IO.print("bye")
+    System.print("hi") // Newline.
+    System.print("bye")
 
 Sometimes, though, a statement doesn't fit on a single line and jamming a
 newline in the middle would trip it up. To handle that, Wren has a very simple
 rule: It ignores a newline following any token that can't end a statement.
 
     :::dart
-    IO.print( // Newline here is ignored.
+    System.print( // Newline here is ignored.
         "hi")
 
 In practice, this means you can put each statement on its own line and wrap
@@ -79,16 +79,16 @@ statement for the else:
     :::dart
     if (happy && knowIt) {
       hands.clap
-    } else IO.print("sad")
+    } else System.print("sad")
 
 Blocks have two similar but not identical forms. Typically, blocks contain a
 series of statements like:
 
     :::dart
     {
-      IO.print("one")
-      IO.print("two")
-      IO.print("three")
+      System.print("one")
+      System.print("two")
+      System.print("three")
     }
 
 Blocks of this form when used for method and function bodies automatically

doc/site/template-core.html

@@ -38,7 +38,7 @@
         <li><a href="range.html">Range</a></li>
         <li><a href="sequence.html">Sequence</a></li>
         <li><a href="string.html">String</a></li>
-        <li><a href="io.html">IO</a></li>
+        <li><a href="system.html">System</a></li>
       </ul>
     </section>
   </nav>

doc/site/values.markdown

@@ -57,11 +57,11 @@ A handful of escape characters are supported:
 A `\u` followed by four hex digits can be used to specify a Unicode code point:
 
     :::dart
-    IO.print("\u0041\u0b83\u00DE") // "AஃÞ"
+    System.print("\u0041\u0b83\u00DE") // "AஃÞ"
 
 A `\x` followed by two hex digits specifies a single unencoded byte:
 
-    IO.print("\x48\x69\x2e") // "Hi."
+    System.print("\x48\x69\x2e") // "Hi."
 
 Strings are instances of class [String](core/string.html).
 
@@ -90,7 +90,7 @@ example:
     :::dart
     var list = ["a", "b", "c", "d", "e"]
     var slice = list[1..3]
-    IO.print(slice) // ["b", "c", "d"]
+    System.print(slice) // ["b", "c", "d"]
 
 Their class is [Range](core/range.html).
 

doc/site/variables.markdown

@@ -13,7 +13,7 @@ defined, it can be accessed by name as you would expect.
 
     :::dart
     var animal = "Slow Loris"
-    IO.print(animal) // Prints "Slow Loris".
+    System.print(animal) // Prints "Slow Loris".
 
 ## Scope
 
@@ -22,11 +22,11 @@ until the end of the [block](syntax.html#blocks) where that definition appears.
 
     :::dart
     {
-      IO.print(a) // ERROR! a doesn't exist yet.
+      System.print(a) // ERROR! a doesn't exist yet.
       var a = 123
-      IO.print(a) // "123"
+      System.print(a) // "123"
     }
-    IO.print(a) // ERROR! a doesn't exist anymore.
+    System.print(a) // ERROR! a doesn't exist anymore.
 
 Variables defined at the top level of a script are *top-level* and are visible
 to the [module](modules.html) system. All other variables are *local*.
@@ -38,9 +38,9 @@ intend to do much).
     var a = "outer"
     {
       var a = "inner"
-      IO.print(a) // Prints "inner".
+      System.print(a) // Prints "inner".
     }
-    IO.print(a) // Prints "outer".
+    System.print(a) // Prints "outer".
 
 Declaring a variable with the same name in the *same* scope *is* an error.
 
@@ -65,6 +65,6 @@ assigned value.
 
     :::dart
     var a = "before"
-    IO.print(a = "after") // Prints "after".
+    System.print(a = "after") // Prints "after".
 
 **TODO: Top-level names.**