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-rw-r--r--build2/function.hxx6
1 files changed, 5 insertions, 1 deletions
diff --git a/build2/function.hxx b/build2/function.hxx
index 139f1fa..5b84a69 100644
--- a/build2/function.hxx
+++ b/build2/function.hxx
@@ -46,12 +46,16 @@ namespace build2
// are conceptually "moved" and can be reused by the implementation.
//
// A function can also optionally receive the current scope by having the
- // first argument of the const scope* type. It may be NULL is the function
+ // first argument of the const scope* type. It may be NULL if the function
// is called out of any scope (e.g., command line).
//
// Note also that we don't pass the location to the function instead
// printing the info message pointing to the call site.
//
+ // A function can return value or anything that can be converted to value.
+ // In particular, if a function returns optional<T>, then the result will be
+ // either NULL or value of type T.
+ //
// Normally functions come in families that share a common qualification
// (e.g., string. or path.). The function_family class is a "registrar"
// that simplifies handling of function families. For example: