"IO" -> "System".

Get rid of the separate opt-in IO class and replace it with a core
System class.

- Remove wren_io.c, wren_io.h, and io.wren.
- Remove the flags that disable it.
- Remove the overloads for print() with different arity. (It was an
  experiment, but I don't think it's that useful.)
- Remove IO.read(). That will reappear using libuv in the CLI at some
  point.
- Remove IO.time. Doesn't seem to have been used.
- Update all of the tests, docs, etc.

I'm sorry for all the breakage this causes, but I think "System" is a
better name for this class (it makes it natural to add things like
"System.gc()") and frees up "IO" for referring to the CLI's IO module.

test/core/map/churn.wren

@@ -8,4 +8,4 @@ for (i in 0...100) {
   if (i >= 10) map.remove(i - 10)
 }
 
-IO.print(map.count) // expect: 10
+System.print(map.count) // expect: 10

test/core/map/clear.wren

@@ -1,7 +1,7 @@
 var a = {1: 1, 2: 2, 3: 3}
 a.clear()
-IO.print(a)       // expect: {}
-IO.print(a.count) // expect: 0
+System.print(a)       // expect: {}
+System.print(a.count) // expect: 0
 
 // Returns null.
-IO.print({1: 2}.clear()) // expect: null
+System.print({1: 2}.clear()) // expect: null

test/core/map/contains_key.wren

@@ -4,8 +4,8 @@ var map = {
   "three": 3
 }
 
-IO.print(map.containsKey("one")) // expect: true
-IO.print(map.containsKey("two")) // expect: true
-IO.print(map.containsKey("three")) // expect: true
-IO.print(map.containsKey("four")) // expect: false
-IO.print(map.containsKey("five")) // expect: false
+System.print(map.containsKey("one")) // expect: true
+System.print(map.containsKey("two")) // expect: true
+System.print(map.containsKey("three")) // expect: true
+System.print(map.containsKey("four")) // expect: false
+System.print(map.containsKey("five")) // expect: false

test/core/map/count.wren

@@ -1,12 +1,12 @@
 var map = {}
-IO.print(map.count) // expect: 0
+System.print(map.count) // expect: 0
 map["one"] = "value"
-IO.print(map.count) // expect: 1
+System.print(map.count) // expect: 1
 map["two"] = "value"
-IO.print(map.count) // expect: 2
+System.print(map.count) // expect: 2
 map["three"] = "value"
-IO.print(map.count) // expect: 3
+System.print(map.count) // expect: 3
 
 // Adding existing key does not increase count.
 map["two"] = "new value"
-IO.print(map.count) // expect: 3
+System.print(map.count) // expect: 3

test/core/map/empty_string_key.wren

@@ -2,4 +2,4 @@ var map = {
   "": "empty string"
 }
 
-IO.print(map[""]) // expect: empty string
+System.print(map[""]) // expect: empty string

test/core/map/key_iterate.wren

@@ -4,23 +4,23 @@ var a = {"one": 1, "two": 2, "three": 3, "four": 4}.keys
 // entry table and the hashing process isn't specified. So we just validate
 // what we can assume about them.
 
-IO.print(a.iterate(null) is Num) // expect: true
-IO.print(a.iterate(null) >= 0) // expect: true
+System.print(a.iterate(null) is Num) // expect: true
+System.print(a.iterate(null) >= 0) // expect: true
 
-IO.print(a.iterate(0) is Num) // expect: true
-IO.print(a.iterate(0) > 0) // expect: true
-IO.print(a.iterate(1) is Num) // expect: true
-IO.print(a.iterate(1) > 0) // expect: true
-IO.print(a.iterate(2) is Num) // expect: true
-IO.print(a.iterate(2) > 0) // expect: true
-IO.print(a.iterate(3) is Num) // expect: true
-IO.print(a.iterate(3) > 0) // expect: true
+System.print(a.iterate(0) is Num) // expect: true
+System.print(a.iterate(0) > 0) // expect: true
+System.print(a.iterate(1) is Num) // expect: true
+System.print(a.iterate(1) > 0) // expect: true
+System.print(a.iterate(2) is Num) // expect: true
+System.print(a.iterate(2) > 0) // expect: true
+System.print(a.iterate(3) is Num) // expect: true
+System.print(a.iterate(3) > 0) // expect: true
 
 var previous = -1
 var iterator = a.iterate(null)
 while (iterator) {
-  IO.print(iterator > previous)
-  IO.print(iterator is Num)
+  System.print(iterator > previous)
+  System.print(iterator is Num)
   previous = iterator
   iterator = a.iterate(iterator)
 }
@@ -38,8 +38,8 @@ while (iterator) {
 // expect: true
 
 // Out of bounds.
-IO.print(a.iterate(16)) // expect: false
-IO.print(a.iterate(-1)) // expect: false
+System.print(a.iterate(16)) // expect: false
+System.print(a.iterate(-1)) // expect: false
 
 // Nothing to iterate in an empty map.
-IO.print({}.keys.iterate(null)) // expect: false
+System.print({}.keys.iterate(null)) // expect: false

test/core/map/key_types.wren

@@ -12,17 +12,17 @@ var map = {
   fiber: "fiber"
 }
 
-IO.print(map[null]) // expect: null value
-IO.print(map[true]) // expect: true value
-IO.print(map[false]) // expect: false value
-IO.print(map[0]) // expect: zero
-IO.print(map[1.2]) // expect: 1 point 2
-IO.print(map[List]) // expect: list class
-IO.print(map["null"]) // expect: string value
-IO.print(map[1..3]) // expect: 1 to 3
-IO.print(map[fiber]) // expect: fiber
+System.print(map[null]) // expect: null value
+System.print(map[true]) // expect: true value
+System.print(map[false]) // expect: false value
+System.print(map[0]) // expect: zero
+System.print(map[1.2]) // expect: 1 point 2
+System.print(map[List]) // expect: list class
+System.print(map["null"]) // expect: string value
+System.print(map[1..3]) // expect: 1 to 3
+System.print(map[fiber]) // expect: fiber
 
-IO.print(map.count) // expect: 9
+System.print(map.count) // expect: 9
 
 // Use the same keys (but sometimes different objects) to ensure keys have the
 // right equality semantics.
@@ -35,13 +35,13 @@ map[[].type] = "new list class"
 map["nu" + "ll"] = "new string value"
 map[(3 - 2)..(1 + 2)] = "new 1 to 3"
 
-IO.print(map[null]) // expect: new null value
-IO.print(map[true]) // expect: new true value
-IO.print(map[false]) // expect: new false value
-IO.print(map[0]) // expect: new zero
-IO.print(map[1.2]) // expect: new 1 point 2
-IO.print(map[List]) // expect: new list class
-IO.print(map["null"]) // expect: new string value
-IO.print(map[1..3]) // expect: new 1 to 3
+System.print(map[null]) // expect: new null value
+System.print(map[true]) // expect: new true value
+System.print(map[false]) // expect: new false value
+System.print(map[0]) // expect: new zero
+System.print(map[1.2]) // expect: new 1 point 2
+System.print(map[List]) // expect: new list class
+System.print(map["null"]) // expect: new string value
+System.print(map[1..3]) // expect: new 1 to 3
 
-IO.print(map.count) // expect: 9
+System.print(map.count) // expect: 9

test/core/map/new.wren

@@ -1,4 +1,4 @@
 var map = Map.new()
 
-IO.print(map.count) // expect: 0
-IO.print(map) // expect: {}
+System.print(map.count) // expect: 0
+System.print(map) // expect: {}

test/core/map/remove.wren

@@ -4,15 +4,15 @@ var map = {
   "three": 3
 }
 
-IO.print(map.count) // expect: 3
-IO.print(map.remove("two")) // expect: 2
-IO.print(map.count) // expect: 2
-IO.print(map.remove("three")) // expect: 3
-IO.print(map.count) // expect: 1
+System.print(map.count) // expect: 3
+System.print(map.remove("two")) // expect: 2
+System.print(map.count) // expect: 2
+System.print(map.remove("three")) // expect: 3
+System.print(map.count) // expect: 1
 
 // Remove an already removed entry.
-IO.print(map.remove("two")) // expect: null
-IO.print(map.count) // expect: 1
+System.print(map.remove("two")) // expect: null
+System.print(map.count) // expect: 1
 
-IO.print(map.remove("one")) // expect: 1
-IO.print(map.count) // expect: 0
+System.print(map.remove("one")) // expect: 1
+System.print(map.count) // expect: 0

test/core/map/subscript_empty_map.wren

@@ -1,4 +1,4 @@
 // This is a regression test to ensure map handles a null entry array.
 
 var map = {}
-IO.print(map["key"]) // expect: null
+System.print(map["key"]) // expect: null

test/core/map/to_string.wren

@@ -1,11 +1,11 @@
 // Handle empty map.
-IO.print({}.toString)             // expect: {}
+System.print({}.toString)             // expect: {}
 
 // Does not quote strings.
-IO.print({"1": "2"}.toString) // expect: {1: 2}
+System.print({"1": "2"}.toString) // expect: {1: 2}
 
 // Nested maps.
-IO.print({1: {2: {}}}) // expect: {1: {2: {}}}
+System.print({1: {2: {}}}) // expect: {1: {2: {}}}
 
 // Calls toString on elements.
 class Foo {
@@ -13,12 +13,12 @@ class Foo {
   toString { "Foo.toString" }
 }
 
-IO.print({1: Foo.new()}) // expect: {1: Foo.toString}
+System.print({1: Foo.new()}) // expect: {1: Foo.toString}
 
 // Since iteration order is unspecified, we don't know what order the results
 // will be.
 var s = {1: 2, 3: 4, 5: 6}.toString
-IO.print(s == "{1: 2, 3: 4, 5: 6}" ||
+System.print(s == "{1: 2, 3: 4, 5: 6}" ||
          s == "{1: 2, 5: 6, 3: 4}" ||
          s == "{3: 4, 1: 2, 5: 6}" ||
          s == "{3: 4, 5: 6, 1: 2}" ||

test/core/map/type.wren

@@ -1,5 +1,5 @@
-IO.print({} is Map)      // expect: true
+System.print({} is Map)      // expect: true
 // TODO: Abstract base class for associations.
-IO.print({} is Object)    // expect: true
-IO.print({} is Bool)      // expect: false
-IO.print({}.type == Map) // expect: true
+System.print({} is Object)    // expect: true
+System.print({} is Bool)      // expect: false
+System.print({}.type == Map) // expect: true

test/core/map/value_iterate.wren

@@ -4,23 +4,23 @@ var a = {"one": 1, "two": 2, "three": 3, "four": 4}.values
 // entry table and the hashing process isn't specified. So we just validate
 // what we can assume about them.
 
-IO.print(a.iterate(null) is Num) // expect: true
-IO.print(a.iterate(null) >= 0) // expect: true
+System.print(a.iterate(null) is Num) // expect: true
+System.print(a.iterate(null) >= 0) // expect: true
 
-IO.print(a.iterate(0) is Num) // expect: true
-IO.print(a.iterate(0) > 0) // expect: true
-IO.print(a.iterate(1) is Num) // expect: true
-IO.print(a.iterate(1) > 0) // expect: true
-IO.print(a.iterate(2) is Num) // expect: true
-IO.print(a.iterate(2) > 0) // expect: true
-IO.print(a.iterate(3) is Num) // expect: true
-IO.print(a.iterate(3) > 0) // expect: true
+System.print(a.iterate(0) is Num) // expect: true
+System.print(a.iterate(0) > 0) // expect: true
+System.print(a.iterate(1) is Num) // expect: true
+System.print(a.iterate(1) > 0) // expect: true
+System.print(a.iterate(2) is Num) // expect: true
+System.print(a.iterate(2) > 0) // expect: true
+System.print(a.iterate(3) is Num) // expect: true
+System.print(a.iterate(3) > 0) // expect: true
 
 var previous = -1
 var iterator = a.iterate(null)
 while (iterator) {
-  IO.print(iterator > previous)
-  IO.print(iterator is Num)
+  System.print(iterator > previous)
+  System.print(iterator is Num)
   previous = iterator
   iterator = a.iterate(iterator)
 }
@@ -38,8 +38,8 @@ while (iterator) {
 // expect: true
 
 // Out of bounds.
-IO.print(a.iterate(16)) // expect: false
-IO.print(a.iterate(-1)) // expect: false
+System.print(a.iterate(16)) // expect: false
+System.print(a.iterate(-1)) // expect: false
 
 // Nothing to iterate in an empty map.
-IO.print({}.values.iterate(null)) // expect: false
+System.print({}.values.iterate(null)) // expect: false