Make it an error to skip or take a negative count.

test/core/sequence/skip.wren

@@ -15,14 +15,11 @@ var test = TestSequence.new().skip(0)
 System.print(test is Sequence) // expect: true
 System.print(test) // expect: instance of SkipSequence
 
-// Skipping 0 changes nothing
+// Skipping 0 changes nothing.
 System.print(test.toList) // expect: [1, 2, 3]
 
-// Skipping 1 works
+// Skipping 1 works.
 System.print(test.skip(1).toList) // expect: [2, 3]
 
-// Skipping more than length of sequence produces empty list
+// Skipping more than length of sequence produces empty list.
 System.print(test.skip(4).isEmpty) // expect: true
-
-// Skipping less than 0 changes nothing
-System.print(test.skip(-10).toList) // expect: [1, 2, 3]

test/core/sequence/skip_negative.wren

@@ -0,0 +1 @@
+[1, 2, 3].skip(-1) // expect runtime error: Count must be a non-negative integer.

test/core/sequence/skip_not_int.wren

@@ -0,0 +1 @@
+[1, 2, 3].skip(1.2) // expect runtime error: Count must be a non-negative integer.

test/core/sequence/skip_not_num.wren

@@ -0,0 +1 @@
+[1, 2, 3].skip("s") // expect runtime error: Count must be a non-negative integer.

test/core/sequence/take.wren

@@ -15,14 +15,11 @@ var test = TestSequence.new().take(3)
 System.print(test is Sequence) // expect: true
 System.print(test) // expect: instance of TakeSequence
 
-// Taking 0 produces empty list
+// Taking 0 produces empty list.
 System.print(test.take(0).isEmpty) // expect: true
 
-// Taking 1 works
+// Taking 1 works.
 System.print(test.take(1).toList) // expect: [1]
 
-// Taking more than length of sequence produces whole sequence
+// Taking more than length of sequence produces whole sequence.
 System.print(test.take(4).toList) // expect: [1, 2, 3]
-
-// Taking less than 0 produces empty list
-System.print(test.take(-10).isEmpty) // expect: true

test/core/sequence/take_negative.wren

@@ -0,0 +1 @@
+[1, 2, 3].take(-1) // expect runtime error: Count must be a non-negative integer.

test/core/sequence/take_not_int.wren

@@ -0,0 +1 @@
+[1, 2, 3].take(1.2) // expect runtime error: Count must be a non-negative integer.

test/core/sequence/take_not_num.wren

@@ -0,0 +1 @@
+[1, 2, 3].take("s") // expect runtime error: Count must be a non-negative integer.