From 4738677d0b75e48874d436022d32441684e2d6e6 Mon Sep 17 00:00:00 2001 From: Thien-Thi Nguyen Date: Mon, 3 Jun 2002 03:15:34 +0000 Subject: [PATCH] Initial revision --- admin/notes/iftc | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) create mode 100644 admin/notes/iftc 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. -- 2.39.5