From: Thien-Thi Nguyen <ttn@gnuvola.org>
Date: Mon, 3 Jun 2002 03:15:34 +0000 (+0000)
Subject: Initial revision
X-Git-Tag: ttn-vms-21-2-B4~14782
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=4738677d0b75e48874d436022d32441684e2d6e6;p=emacs.git

Initial revision
---

diff --git a/admin/notes/iftc b/admin/notes/iftc
new file mode 100644
index 00000000000..294464a8605
--- /dev/null
+++ b/admin/notes/iftc
@@ -0,0 +1,25 @@
+Iso-Functional Type Contour
+
+
+This is a term coined to describe "column int->float" change approach, and can
+be used whenever low-level types need to change (hopefully not often!) but the
+meanings of the values (whose type has changed) do not.
+
+The premise is that changing a low-level type potentially means lots of code
+needs to be changed as well, and the question is how to do this incrementally,
+which is the preferred way to change things.
+
+Say LOW and HIGH are C functions:
+
+  int LOW (void) { return 1; }
+  void HIGH (void) { int value = LOW (); }
+
+We want to convert LOW to return float, so we cast HIGH usage:
+
+  float LOW (void) { return 1.0; }
+  void HIGH (void) { int value = (int) LOW (); }  /* iftc */
+
+The comment /* iftc */ is used to mark this type of casting to differentiate
+it from other casting.  We commit the changes and can now go about modifying
+LOW and HIGH separately.  When HIGH is ready to handle the type change, the
+cast can be removed.