First draft of seqs

content/seqs.md

@@ -4,30 +4,50 @@ title: Seqs
 
 # Seqs
 
-Seqs provide dynamically expandable storage, they are extended as needed. There are two ways to create seqs, with the `@` operator and with the `newSeq[T](n: int)` method.
+Seqs provide dynamically expandable storage, they are extended as needed.
+
+There are two ways to create seqs, with the `@` operator and with the `newSeq[T](n: int)` method. Once a seq is created, it can be modified using the `add(item: T)`, `remove(idx: int)`. The length of a seq can be found through `len: int`, and the maximum index through `high: int`. The standard `items: T` and `pairs: tuple[i: int, v: T]` iterators are also available.
+
+``` nimrod
+var
+  a = @[1, 2, 3]
+  b = newSeq[int](3)
+
+for i, v in a:
+  b[i] = v*v
+
+for i in 4..100:
+  b.add(i * i)
+
+b.remove(0)  # takes «O(n)» time
+b = a[0] & b  # Same as original b
+```
+
+
+## Value semantics
 
 Seqs have value semantics, so
 
 ``` nimrod
 let a = @[1, 2, 3]
-a[1] = 5
+a.add(4)
 ```
 
 will fail to compile because `a` cannot be assigned to. However, 
 
 ``` nimrod
 var b = @[1, 2, 3]
-b[1] = 5
+b.add(4)
 ```
 
 will work without any problems. If wanted, a seq can be passed to a method with the `var` annotation to make it modifiable, so
 
 ``` nimrod
 proc foo(mySeq: var seq[int]) =
-  mySeq[0] = 999
+  mySeq[9] = 999
 
-var thisSeq = @[1, 2, 3, 4]
+var thisSeq = newSeq[int](10)
 foo(thisSeq)
 
-assert thisSeq[0] == 999
+assert thisSeq[9] == 999
 ```