define compile-time vs runtime behavior

1 files changed, 24 insertions, 6 deletions

diff --git a/language/functions.rst b/language/functions.rst
index 86d1144..22a61a3 100644
--- a/language/functions.rst
+++ b/language/functions.rst
@@ -3,18 +3,36 @@ Functions
 
 .. crowbar:element:: FunctionDeclaration <- FunctionSignature ';'
 
-    A function declaration defines the return type, name, and arguments of a function without specifying its behavior.
-    It is generally used as part of an API boundary.
+    Compile-time Behavior:
+
+    Provides a declaration of a function with the name, return type, and arguments specified by the signature, but does not specify any behavior.
+    This is generally used as part of an API boundary.
+
+    Runtime Behavior:
+
+    A function declaration has no runtime behavior.
 
 .. crowbar:element:: FunctionDefinition <- FunctionSignature Block
 
-    A function definition provides the actual behavior of a function, which may have been declared previously or may not.
+    Compile-time Behavior:
+
+    Provides the actual behavior of a function, which may have been declared previously or may not.
+    If the function was declared in some ``.hro`` file which was :crowbar:ref:`include <IncludeStatement>`\ d, the function must be exported and available for external use in the compiler's output.
+    Otherwise, the function should not be exported.
+
+    If the function signature specifies a return type other than ``void``, but there are paths through the block that do not execute a :crowbar:ref:`ReturnStatement`, the compiler must give an error.
 
-    .. todo::
+    Runtime Behavior:
 
-        define function linkage/exportedness
+    When the function is called, the arguments must be populated and the block must be executed.
 
 .. crowbar:element:: FunctionSignature <- Type identifier '(' SignatureArguments? ')'
                      SignatureArguments <- Type identifier (',' Type identifier)* ','?
-    
+
+    Compile-time Behavior:
+
     A function signature specifies the return type, name, and arguments of a function.
+
+    Runtime Behavior:
+
+    A function signature has no runtime behavior.