Clean up of section 1

scala.html.markdown

@@ -32,23 +32,36 @@ Scala - the scalable language
 ## 1. Basics
 #################################################
 
+// Single line comments start with two forward slashes
+
+/*
+  Multi line comments, as you can already see from above, look like this.
+*/
+
 // Printing, and forcing a new line on the next print
 println("Hello world!")
+println(10)
+
 // Printing, without forcing a new line on next print
 print("Hello world")
 
-// Declaring values is done using either var or val
+// Declaring values is done using either var or val.
 // val declarations are immutable, whereas var's are mutable. Immutability is
 // a good thing.
 val x = 10 // x is now 10
 x = 20 // error: reassignment to val
-var x = 10
+var y = 10
-x = 20  // x is now 20
+y = 20  // y is now 20
 
-//  Single line comments start with two forward slashes
 /*
-Multi line comments look like this.
+  Scala is a statically typed language, yet note that in the above declarations, we did not specify
+  a type. This is due to a language feature called type inference. In most cases, Scala compiler can
+  guess what the type of a variable is, so you don't have to type it every time. We can explicitly
+  declare the type of a variable like so:
 */
+val z: Int = 10
+val a: Double = 1.0
+val b: Double = 10  // Notice automatic conversion from Int to Double, result is 10.0, not 10
 
 // Boolean values
 true
@@ -65,9 +78,11 @@ true == false // false
 2 - 1 // 1
 5 * 3 // 15
 6 / 2 // 3
+6 / 4 // 1
+6.0 / 4 // 1.5
 
 
-// Evaluating a command in the REPL gives you the type and value of the result
+// Evaluating an expression in the REPL gives you the type and value of the result
 
 1 + 7
 
@@ -79,48 +94,46 @@ true == false // false
   This means the result of evaluating 1 + 7 is an object of type Int with a
   value of 8
 
-  1+7 will give you the same result
+  Note that "res29" is a sequentially generated variable name to store the results of the
+  expressions you typed, your output may differ.
 */
 
-
+"Scala strings are surrounded by double quotes"
-// Strings
-
-"Scala strings are surrounded by double quotes" //
 'a' // A Scala Char
 'Single quote strings don't exist' // Error
-"Strings have the usual Java methods defined on them".length
-"They also have some extra Scala methods.".reverse
 
-// Seealso:  scala.collection.immutable.StringOps
+// Strings have the usual Java methods defined on them
+"hello world".length
+"ABCDEF".substring(2, 6)
+"ABCDEF".replace("C", "3")
 
-println("ABCDEF".length)
+// They also have some extra Scala methods. See also: scala.collection.immutable.StringOps
-println("ABCDEF".substring(2, 6))
+"hello world".take(5)
-println("ABCDEF".replace("C", "3"))
 
-// String interpolation
+// String interpolation: notice the prefix "s"
 val n = 45
-println(s"We have $n apples") // => "We have 45 apples"
+s"We have $n apples" // => "We have 45 apples"
 
 // Expressions inside interpolated strings are also possible
 val a = Array(11, 9, 6)
-println(s"My second daughter is ${a(0) - a(2)} years old.") // => "My second daughter is 5 years old."
+s"My second daughter is ${a(0) - a(2)} years old." // => "My second daughter is 5 years old."
-println(s"We have double the amount of ${n / 2.0} in apples.") // => "We have double the amount of 22.5 in apples."
+s"We have double the amount of ${n / 2.0} in apples." // => "We have double the amount of 22.5 in apples."
-println(s"Power of 2: ${math.pow(2, 2)}") // => "Power of 2: 4"
+s"Power of 2: ${math.pow(2, 2)}" // => "Power of 2: 4"
 
-// Formatting with interpolated strings (note the prefixed f)
+// Formatting with interpolated strings with the prefix "f"
-println(f"Power of 5: ${math.pow(5, 2)}%1.0f") // "Power of 5: 25"
+f"Power of 5: ${math.pow(5, 2)}%1.0f" // "Power of 5: 25"
-println(f"Square root of 122: ${math.sqrt(122)}%1.4f") // "Square root of 122"
+f"Square root of 122: ${math.sqrt(122)}%1.4f" // "Square root of 122"
 
-// Ignoring special characters.
+// Raw strings, ignoring special characters.
-println(raw"New line feed: \n. Carriage return: \r.") // => "New line feed: \n. Carriage return: \r."
+raw"New line feed: \n. Carriage return: \r." // => "New line feed: \n. Carriage return: \r."
 
-// Some characters need to be 'escaped', e.g. a double quote inside a string:
+// Some characters need to be "escaped", e.g. a double quote inside a string:
-val a = "They stood outside the \"Rose and Crown\"" // => "They stood outside the "Rose and Crown""
+"They stood outside the \"Rose and Crown\"" // => "They stood outside the "Rose and Crown""
 
 // Triple double-quotes let strings span multiple rows and contain quotes
 val html = """<form id="daform">
                 <p>Press belo', Joe</p>
-             |  <input type="submit">
+                <input type="submit">
               </form>"""