Added Sequence.each

This is a bit of a style preference since of course you can always write
the same thing with a for loop. However, I think sometimes the code
looks better when using this method.

It also provides an alternative to Sequence.map for cases where you
don't need the resulting list, and one that becomes especially necessary
when Sequence.map is changed to return a new sequence. The example in
the README.md file was using Sequence.map in a way that required this
alternative in that case.

README.md

@@ -13,7 +13,7 @@ class Wren {
 }
 
 var adjectives = new Fiber {
-  ["small", "clean", "fast"].map {|word| Fiber.yield(word) }
+  ["small", "clean", "fast"].each {|word| Fiber.yield(word) }
 }
 
 while (!adjectives.isDone) IO.print(adjectives.call())

builtin/core.wren

@@ -26,6 +26,12 @@ class Sequence {
     return result
   }
 
+  each(f) {
+    for (element in this) {
+      f.call(element)
+    }
+  }
+
   map(f) {
     var result = new List
     for (element in this) {

doc/site/core/sequence.markdown

@@ -54,6 +54,13 @@ and counting the number of times the returned value evaluates to `true`.
     [1, 2, 3].count {|n| n > 2} // 1.
     [1, 2, 3].count {|n| n < 4} // 3.
 
+### **each**(function)
+
+Iterates over the sequence, passing each element to the given `function`.
+
+    :::dart
+    ["one", "two", "three"].each {|word| IO.print(word) }
+
 ### **join**(sep)
 
 Returns a string representation of the list. The string representations of the

doc/site/index.markdown

@@ -15,7 +15,7 @@ a familiar, modern [syntax][].
     }
 
     var adjectives = new Fiber {
-      ["small", "clean", "fast"].map {|word| Fiber.yield(word) }
+      ["small", "clean", "fast"].each {|word| Fiber.yield(word) }
     }
 
     while (!adjectives.isDone) IO.print(adjectives.call())
@@ -52,4 +52,4 @@ If you like the sound of this, [give it a try][try]! Even better, you can
 [fibers]: fibers.html
 [embedding]: embedding-api.html
 [try]: getting-started.html
-[contribute]: contributing.html
+[contribute]: contributing.html

src/vm/wren_core.c

@@ -72,6 +72,12 @@ static const char* libSource =
 "    return result\n"
 "  }\n"
 "\n"
+"  each(f) {\n"
+"    for (element in this) {\n"
+"      f.call(element)\n"
+"    }\n"
+"  }\n"
+"\n"
 "  map(f) {\n"
 "    var result = new List\n"
 "    for (element in this) {\n"

test/core/list/each.wren

@@ -0,0 +1,3 @@
+var words = ""
+["One", "Two", "Three"].each {|word| words = words + word }
+IO.print(words) // expect: OneTwoThree

test/core/list/each_no_items.wren

@@ -0,0 +1,3 @@
+var i = 0
+[].each {|item| i = i + 1 }
+IO.print(i) // expect: 0

test/core/list/each_non_function_arg.wren

@@ -0,0 +1 @@
+[1, 2, 3].each("string") // expect runtime error: String does not implement 'call(_)'.