Added functionality for more easily testing the Boost Jam version from Jamfiles. Now you can use the version.check-jam-version rule, as in [ versions.check-jam-version 3 1 17 ] which will return true if the current Boost Jam version is at least 3.1.17. Added related internal Boost Build tests for the new functionality.

[SVN r45096]

v2/build/version.jam

@@ -1,7 +1,12 @@
 # Copyright 2002, 2003, 2004, 2006 Vladimir Prus
+# Copyright 2008 Jurko Gospodnetic
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
 
+import errors ;
+import numbers ;
+
+
 rule boost-build ( )
 {
     return "V2 (Milestone 12)" ;
@@ -10,7 +15,7 @@ rule boost-build ( )
 
 rule jam ( )
 {
-    local v = [ modules.peek : JAM_VERSION  ] ;
+    local v = [ modules.peek : JAM_VERSION ] ;
     return $(v:J=.) ;
 }
 
@@ -20,3 +25,117 @@ rule print ( )
     ECHO "Boost.Build" [ boost-build ] ;
     ECHO "Boost.Jam" [ jam ] ;
 }
+
+
+# Utility rule for testing whether all elements of a sequence are equal to 0.
+#
+local rule is-all-zeroes ( sequence * )
+{
+    local result = "true" ;
+    for local e in $(sequence)
+    {
+        if $(e) != "0"
+        {
+            result = "" ;
+        }
+    }
+    return $(result) ;
+}
+
+
+# Returns "true" if the first version is less than the second one.
+#
+rule version-less ( lhs + : rhs + )
+{
+    numbers.check $(lhs) ;
+    numbers.check $(rhs) ;
+
+    local done ;
+    local result ;
+
+    while ! $(done) && $(lhs) && $(rhs)
+    {
+        if [ numbers.less $(lhs[1]) $(rhs[1]) ]
+        {
+            done = "true" ;
+            result = "true" ;
+        }
+        else if [ numbers.less $(rhs[1]) $(lhs[1])  ]
+        {
+            done = "true" ;
+        }
+        else
+        {
+            lhs = $(lhs[2-]) ;
+            rhs = $(rhs[2-]) ;
+        }
+    }
+    if ( ! $(done) && ! $(lhs) && ! [ is-all-zeroes $(rhs) ] )
+    {
+        result = "true" ;
+    }
+    
+    return $(result) ;
+}
+
+
+# Returns "true" if the current JAM version version is at least the given
+# version.
+#
+rule check-jam-version ( version + )
+{
+    local version-tag = $(version:J=.) ;
+    if ! $(version-tag)
+    {
+        errors.error Invalid version specifier: : $(version:E="(undefined)") ;
+    }
+
+    if ! $(.jam-version-check.$(version-tag))-is-defined
+    {
+        local jam-version = [ modules.peek : JAM_VERSION ] ;
+        if ! $(jam-version)
+        {
+            errors.error "Unable to deduce Boost Jam version. Your Boost Jam"
+                "installation is most likely terribly outdated." ;
+        }
+        .jam-version-check.$(version-tag) = "true" ;
+        if [ version-less [ modules.peek : JAM_VERSION ] : $(version) ]
+        {
+            .jam-version-check.$(version-tag) = "" ;
+        }
+    }
+    return $(.jam-version-check.$(version-tag)) ;
+}
+
+
+rule __test__ ( )
+{
+    import assert ;
+    
+    local jam-version = [ modules.peek : JAM_VERSION ] ;
+    local future-version = $(jam-version) ;
+    future-version += "1" ;
+
+    assert.true  check-jam-version $(jam-version)    ;
+    assert.false check-jam-version $(future-version) ;
+
+    assert.true  version-less 0          : 1          ;
+    assert.false version-less 0          : 0          ;
+    assert.true  version-less 1          : 2          ;
+    assert.false version-less 1          : 1          ;
+    assert.false version-less 2          : 1          ;
+    assert.true  version-less 3 1 20     : 3 4 10     ;
+    assert.false version-less 3 1 10     : 3 1 10     ;
+    assert.false version-less 3 4 10     : 3 1 20     ;
+    assert.true  version-less 3 1 20 5 1 : 3 4 10     ;
+    assert.false version-less 3 1 10 5 1 : 3 1 10     ;
+    assert.false version-less 3 4 10 5 1 : 3 1 20     ;
+    assert.true  version-less 3 1 20     : 3 4 10 5 1 ;
+    assert.true  version-less 3 1 10     : 3 1 10 5 1 ;
+    assert.false version-less 3 4 10     : 3 1 20 5 1 ;
+    assert.false version-less 3 1 10     : 3 1 10 0 0 ;
+    assert.false version-less 3 1 10 0 0 : 3 1 10     ;
+    assert.false version-less 3 1 10 0   : 3 1 10 0 0 ;
+
+    # TODO: Add tests for invalid input data being sent to version-less.
+}