Listing of doc/example-scripts/traits-composite.tcl

Index: doc/example-scripts/traits-composite.html =================================================================== diff -u -r93bb0947d582f274afb1cdbc885909d55e100b36 -rc4f449cb353be812ba6502ef8e9587e87881f59b --- doc/example-scripts/traits-composite.html (.../traits-composite.html) (revision 93bb0947d582f274afb1cdbc885909d55e100b36) +++ doc/example-scripts/traits-composite.html (.../traits-composite.html) (revision c4f449cb353be812ba6502ef8e9587e87881f59b) @@ -1,918 +1,918 @@ - - - - - -Listing of doc/example-scripts/traits-composite.tcl - - - - - -

Implementation study based on

-
-Ducasse, O. Nierstrasz, N. Schärli, R. Wuyts, A. Black: -Traits: A Mechanism for Fine-grained Reuse, -ACM transactions on Programming Language Systems, Vol 28, No 2, March 2006 -
-

Fig 13: tReadStream and tWriteStream as composite traits

In this example, traits are used to extend classes and other traits -(called then composite traits).

package req nx::trait

Create a Trait called tPositionableStream

nx::Trait create tPositionableStream {
-  #
-  # Define the methods provided by this trait:
-  #
-  :public method atStart {} {expr {[:position] == [:minPosition]}}
-  :public method atEnd {} {expr {[:position] == [:maxPosition]}}
-  :public method setToStart {} {set :position [:minPosition]}
-  :public method setToEnd {} {set :position [:maxPosition]}
-  :public method maxPosition {} {llength ${:collection}}
-  :public method minPosition {} {return 0}
-  :public method nextPosition {} {incr :position 1}
-
-  # The trait requires a method "position" and a variable "collection"
-  # from the base class or other traits. The definition is incomplete
-  # in these regards
-
-  :requiredMethods position
-  :requiredVariables collection
-}

Create a composite trait called tReadStream based on the trait -tPositionableStream:

nx::Trait create tReadStream {
-  #
-  # Methods provided by this trait:
-  #
-  :public method on {collection} {set :collection $collection; :setToStart}
-  :public method next {} {
-    if {[:atEnd]} {return ""} else {
-      set r [lindex ${:collection} ${:position}]
-      :nextPosition
-      return $r
-    }
-  }
-
-  # This trait requires these methods:
-  :requiredMethods {setToStart atEnd nextPosition}
-
-  # Require the trait "tPositionableStream"
-  :require trait tPositionableStream
-}

Create a composite trait called tWriteStream based on the trait -tPositionableStream:

nx::Trait create tWriteStream {
-  #
-  # Methods provided by this trait:
-  #
-  :public method on {collection} {set :collection $collection; :setToEnd}
-  :public method nextPut {element} {
-    lappend :collection $element
-    :nextPosition
-    return ""
-  }
-
-  # This trait requires these methods:
-  :requiredMethods {setToEnd nextPosition}
-
-  # Require the trait "tPositionableStream"
-  :require trait tPositionableStream
-}

Define a class ReadStream with properties position and -collection that uses the composite trait tReadStream:

nx::Class create ReadStream {
-  :property {collection ""}
-  :property -accessor public {position 0}
-  :require trait tReadStream
-}

Create an instance of ReadStream:

ReadStream create r1 -collection {a b c d e}

Test the behavior of the composed class:

% r1 atStart
-1
-% r1 atEnd
-0
-% r1 next
-a
-% r1 next
-b

- - - + + + + + +Listing of doc/example-scripts/traits-composite.tcl + + + + + +

Implementation study based on

+
+Ducasse, O. Nierstrasz, N. Schärli, R. Wuyts, A. Black: +Traits: A Mechanism for Fine-grained Reuse, +ACM transactions on Programming Language Systems, Vol 28, No 2, March 2006 +
+

Fig 13: tReadStream and tWriteStream as composite traits

In this example, traits are used to extend classes and other traits +(called then composite traits).

package req nx::trait

Create a Trait called tPositionableStream

nx::Trait create tPositionableStream {
+  #
+  # Define the methods provided by this trait:
+  #
+  :public method atStart {} {expr {[:position] == [:minPosition]}}
+  :public method atEnd {} {expr {[:position] == [:maxPosition]}}
+  :public method setToStart {} {set :position [:minPosition]}
+  :public method setToEnd {} {set :position [:maxPosition]}
+  :public method maxPosition {} {llength ${:collection}}
+  :public method minPosition {} {return 0}
+  :public method nextPosition {} {incr :position 1}
+
+  # The trait requires a method "position" and a variable "collection"
+  # from the base class or other traits. The definition is incomplete
+  # in these regards
+
+  :requiredMethods position
+  :requiredVariables collection
+}

Create a composite trait called tReadStream based on the trait +tPositionableStream:

nx::Trait create tReadStream {
+  #
+  # Methods provided by this trait:
+  #
+  :public method on {collection} {set :collection $collection; :setToStart}
+  :public method next {} {
+    if {[:atEnd]} {return ""} else {
+      set r [lindex ${:collection} ${:position}]
+      :nextPosition
+      return $r
+    }
+  }
+
+  # This trait requires these methods:
+  :requiredMethods {setToStart atEnd nextPosition}
+
+  # Require the trait "tPositionableStream"
+  :require trait tPositionableStream
+}

Create a composite trait called tWriteStream based on the trait +tPositionableStream:

nx::Trait create tWriteStream {
+  #
+  # Methods provided by this trait:
+  #
+  :public method on {collection} {set :collection $collection; :setToEnd}
+  :public method nextPut {element} {
+    lappend :collection $element
+    :nextPosition
+    return ""
+  }
+
+  # This trait requires these methods:
+  :requiredMethods {setToEnd nextPosition}
+
+  # Require the trait "tPositionableStream"
+  :require trait tPositionableStream
+}

Define a class ReadStream with properties position and +collection that uses the composite trait tReadStream:

nx::Class create ReadStream {
+  :property {collection ""}
+  :property -accessor public {position 0}
+  :require trait tReadStream
+}

Create an instance of ReadStream:

ReadStream create r1 -collection {a b c d e}

Test the behavior of the composed class:

% r1 atStart
+1
+% r1 atEnd
+0
+% r1 next
+a
+% r1 next
+b

+ + +