Introduce 'incidental' features.

* new/feature.jam: The above change.
    * new/property.jam
      (remove): Renamed & generalized from 'remove-free'.
      (take): Likewise.


[SVN r14752]

new/feature.jam

@@ -73,7 +73,9 @@ import utility ;
         # toolset, always generates a corresponding subvariant
         # directory.
 
-    free        # as described in previous documentation
+    free
+      
+    incidental  
 
     path        # the (free) feature's value describes a path which
         # might be given relative to the directory of the
@@ -318,8 +320,8 @@ local rule expand-subfeatures-aux (
 #
 rule expand-subfeatures ( 
   properties * # property set with elements of the form
-	       # <feature>value-string or just value-string in the
-	       # case of implicit features.
+           # <feature>value-string or just value-string in the
+           # case of implicit features.
 )
 {
     local result ;

new/make.jam

@@ -21,7 +21,7 @@ rule make-target-class ( name : project : sources * : requirements *
     rule construct ( source-targets * : properties * )
     {
         local t = [ new virtual-target $(self.name)
-                    : $(self.project) : [ property.remove-free $(properties) ] ] ;
+                    : $(self.project) : [ property.remove free incidental : $(properties) ] ] ;
         local a = [ new action $(t) : $(source-targets) : $(self.make-rule) 
                     : $(properties) ] ;
         $(t).action $(a) ;

new/property.jam

@@ -201,15 +201,15 @@ rule make ( specification * )
     return $(result) ;
 }
 
-# Returns a property sets which include all the elements in 'properties',
-# except for free properties.
-rule remove-free ( properties * : feature-space ? )
+# Returns a property sets which include all the elements in 'properties' that
+# do not have attributes listed in 'attributes'. 
+rule remove ( attributes + : properties * : feature-space ? )
 {
     feature-space ?= feature ;
     local result ;
     for local e in $(properties)
     {
-        if ! free in [ $(feature-space).attributes $(e:G) ] 
+        if ! [ set.intersection $(attributes) : [ $(feature-space).attributes $(e:G) ] ]
         {
             result += $(e) ;
         }
@@ -217,14 +217,15 @@ rule remove-free ( properties * : feature-space ? )
     return $(result) ;
 }
 
-# Returns a property set which include all free properties in 'properties'.
-rule take-free ( properties * : feature-space ? )
+# Returns a property set which include all properties in 'properties' that have
+# any of 'attributes'.
+rule take ( attributes + : properties * : feature-space ? )
 {
     feature-space ?= feature ;
     local result ;
     for local e in $(properties)
     {
-        if free in [ $(feature-space).attributes $(e:G) ] 
+        if [ set.intersection $(attributes) : [ $(feature-space).attributes $(e:G) ] ]
         {
             result += $(e) ;
         }
@@ -305,7 +306,7 @@ local rule __test__ ( )
     catch "Invalid property 'value': 'value' is not a value of implicit feature." ;
            
 
-    assert.result <toolset>gcc <rtti>on 
-        : remove-free <toolset>gcc <define>foo <rtti>on : $(test-space) ;
+    assert.result <rtti>on 
+        : remove free implicit : <toolset>gcc <define>foo <rtti>on : $(test-space) ;
 }
 

new/targets.jam

@@ -174,7 +174,8 @@ rule main-target ( name : project )
         }
         else
         {
-            # Find the alternative with the longest set of non-free requirements
+            # Find the alternative with the longest set of non-free and 
+            # non-indicental requirements
             local r = [ $(alternatives).indices ] ;
 
             # First compute the length of requirements sets
@@ -184,7 +185,7 @@ rule main-target ( name : project )
                 local target = [ $(alternatives).at $(p) : 1 ] ;
                 assert.equal [ is-a $(target) : basic-target ] : true ;
                 local props = [ $(target).requirements ] ;
-                req-length += [ sequence.length [ property.remove-free 
+                req-length += [ sequence.length [ property.remove free :
                                 [ $(target).requirements ] ] ] ;
             }
 
@@ -211,18 +212,19 @@ rule main-target ( name : project )
             }                    
         } 
 
-        # Add additional subvariant element for the targets which free properties
-        # are not equal to project's.
+        # Add additional subvariant element for the targets which free,
+        # non-incidental properties are not equal to project's.
 
-        local pr = [ property.take-free 
-                       [ project.attribute $(self.project) requirements ] ] ;
+        local pr = [ property.take free : [ property.remove incidental : 
+                       [ project.attribute $(self.project) requirements ] ] ] ;
 
         for local v in $(result)
         {
             local action = [ $(v).action ] ;
             if $(action) 
             {
-                local properties = [ property.take-free [ $(action).properties  ] ] ;
+                local properties = [ property.take free : [ property.remove incidental : 
+                                        [ $(action).properties  ] ] ] ;
         
                 if $(properties) != $(pr)
                 {

v2/build/feature.jam

@@ -73,7 +73,9 @@ import utility ;
         # toolset, always generates a corresponding subvariant
         # directory.
 
-    free        # as described in previous documentation
+    free
+      
+    incidental  
 
     path        # the (free) feature's value describes a path which
         # might be given relative to the directory of the
@@ -318,8 +320,8 @@ local rule expand-subfeatures-aux (
 #
 rule expand-subfeatures ( 
   properties * # property set with elements of the form
-	       # <feature>value-string or just value-string in the
-	       # case of implicit features.
+           # <feature>value-string or just value-string in the
+           # case of implicit features.
 )
 {
     local result ;

v2/build/property.jam

@@ -201,15 +201,15 @@ rule make ( specification * )
     return $(result) ;
 }
 
-# Returns a property sets which include all the elements in 'properties',
-# except for free properties.
-rule remove-free ( properties * : feature-space ? )
+# Returns a property sets which include all the elements in 'properties' that
+# do not have attributes listed in 'attributes'. 
+rule remove ( attributes + : properties * : feature-space ? )
 {
     feature-space ?= feature ;
     local result ;
     for local e in $(properties)
     {
-        if ! free in [ $(feature-space).attributes $(e:G) ] 
+        if ! [ set.intersection $(attributes) : [ $(feature-space).attributes $(e:G) ] ]
         {
             result += $(e) ;
         }
@@ -217,14 +217,15 @@ rule remove-free ( properties * : feature-space ? )
     return $(result) ;
 }
 
-# Returns a property set which include all free properties in 'properties'.
-rule take-free ( properties * : feature-space ? )
+# Returns a property set which include all properties in 'properties' that have
+# any of 'attributes'.
+rule take ( attributes + : properties * : feature-space ? )
 {
     feature-space ?= feature ;
     local result ;
     for local e in $(properties)
     {
-        if free in [ $(feature-space).attributes $(e:G) ] 
+        if [ set.intersection $(attributes) : [ $(feature-space).attributes $(e:G) ] ]
         {
             result += $(e) ;
         }
@@ -305,7 +306,7 @@ local rule __test__ ( )
     catch "Invalid property 'value': 'value' is not a value of implicit feature." ;
            
 
-    assert.result <toolset>gcc <rtti>on 
-        : remove-free <toolset>gcc <define>foo <rtti>on : $(test-space) ;
+    assert.result <rtti>on 
+        : remove free implicit : <toolset>gcc <define>foo <rtti>on : $(test-space) ;
 }
 

v2/build/targets.jam

@@ -174,7 +174,8 @@ rule main-target ( name : project )
         }
         else
         {
-            # Find the alternative with the longest set of non-free requirements
+            # Find the alternative with the longest set of non-free and 
+            # non-indicental requirements
             local r = [ $(alternatives).indices ] ;
 
             # First compute the length of requirements sets
@@ -184,7 +185,7 @@ rule main-target ( name : project )
                 local target = [ $(alternatives).at $(p) : 1 ] ;
                 assert.equal [ is-a $(target) : basic-target ] : true ;
                 local props = [ $(target).requirements ] ;
-                req-length += [ sequence.length [ property.remove-free 
+                req-length += [ sequence.length [ property.remove free :
                                 [ $(target).requirements ] ] ] ;
             }
 
@@ -211,18 +212,19 @@ rule main-target ( name : project )
             }                    
         } 
 
-        # Add additional subvariant element for the targets which free properties
-        # are not equal to project's.
+        # Add additional subvariant element for the targets which free,
+        # non-incidental properties are not equal to project's.
 
-        local pr = [ property.take-free 
-                       [ project.attribute $(self.project) requirements ] ] ;
+        local pr = [ property.take free : [ property.remove incidental : 
+                       [ project.attribute $(self.project) requirements ] ] ] ;
 
         for local v in $(result)
         {
             local action = [ $(v).action ] ;
             if $(action) 
             {
-                local properties = [ property.take-free [ $(action).properties  ] ] ;
+                local properties = [ property.take free : [ property.remove incidental : 
+                                        [ $(action).properties  ] ] ] ;
         
                 if $(properties) != $(pr)
                 {

v2/tools/make.jam

@@ -21,7 +21,7 @@ rule make-target-class ( name : project : sources * : requirements *
     rule construct ( source-targets * : properties * )
     {
         local t = [ new virtual-target $(self.name)
-                    : $(self.project) : [ property.remove-free $(properties) ] ] ;
+                    : $(self.project) : [ property.remove free incidental : $(properties) ] ] ;
         local a = [ new action $(t) : $(source-targets) : $(self.make-rule) 
                     : $(properties) ] ;
         $(t).action $(a) ;