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/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.