extension methids

docs/OOP.md

@@ -160,6 +160,40 @@ For example, for our class Point:
     Point(1,1+1)
     >>> Point(x=1,y=2)
 
+# Extending classes
+
+It sometimes happen that the class is missing some particular functionality that can be _added to it_ without rewriting its inner logic and using its private state. In this case _extension methods_ could be used, for example. we want to create an extension method
+that would test if some object of unknown type contains something that can be interpreted
+as an integer. In this case we _extend_ class `Object`, as it is the parent class for any instance of any type:
+
+        fun Object.isInteger() {
+            when(this) {
+                // already Int?
+                is Int -> true
+
+                // real, but with no declimal part?
+                is Real -> toInt() == this
+
+                // string with int or real reuusig code above
+                is String -> toReal().isInteger()
+                
+                // otherwise, no:
+                else -> false
+            }
+        }
+
+        // Let's test:        
+        assert( 12.isInteger() == true )
+        assert( 12.1.isInteger() == false )
+        assert( "5".isInteger() )
+        assert( ! "5.2".isInteger() )
+        >>> void
+
+__Important note__ as for version 0.6.9, extensions are in __global scope__. It means, that once applied to a global type (Int in our sample), they will be available for _all_ contexts, even new created, 
+as they are modifying the type, not the context.
+
+Beware of it. We might need to reconsider it later.
+
 # Theory
 
 ## Basic principles:

docs/Real.md

@@ -15,11 +15,11 @@ you can use it's class to ensure type:
 
 ## Member functions
 
-| name            | meaning                            | type |
-|-----------------|------------------------------------|------|
-| `.roundToInt()` | round to nearest int like round(x) | Int  |
-|                 |                                    |      |
-|                 |                                    |      |
-|                 |                                    |      |
-|                 |                                    |      |
-|                 |                                    |      |
+| name            | meaning                                                     | type |
+|-----------------|-------------------------------------------------------------|------|
+| `.roundToInt()` | round to nearest int like round(x)                          | Int  |
+| `.toInt()`      | convert integer part of real to `Int` dropping decimal part | Int  |
+|                 |                                                             |      |
+|                 |                                                             |      |
+|                 |                                                             |      |
+|                 |                                                             |      |

docs/tutorial.md

@@ -1214,6 +1214,9 @@ Typical set of String functions includes:
 | [Range]            | substring at range                                         |
 | s1 + s2            | concatenation                                              |
 | s1 += s2           | self-modifying concatenation                               |
+| toReal()           | attempts to parse string as a Real value                   |
+|                    |                                                            |
+|                    |                                                            |