Add new record type syntax.

* sly/record.scm: New file.
* Makefile.am (SOURCES): Add it.

2 files changed, 55 insertions, 0 deletions

diff --git a/Makefile.am b/Makefile.am
index dad4409..f7aa9cf 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -42,6 +42,7 @@ SOURCES = 					\
   sly/repl.scm					\
   sly/signal.scm				\
   sly/window.scm				\
+  sly/record.scm				\
   sly/render/utils.scm				\
   sly/render/color.scm				\
   sly/render/camera.scm				\
diff --git a/sly/record.scm b/sly/record.scm
new file mode 100644
index 0000000..8221b14
--- /dev/null
+++ b/sly/record.scm
@@ -0,0 +1,54 @@
+;;; Sly
+;;; Copyright (C) 2015 David Thompson <davet@gnu.org>
+;;;
+;;; This program is free software: you can redistribute it and/or
+;;; modify it under the terms of the GNU General Public License as
+;;; published by the Free Software Foundation, either version 3 of the
+;;; License, or (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with this program.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; Immutable record type syntax with keyword argument constructor,
+;; field inheritance, and default field values.
+;;
+;;; Code:
+
+(define-module (sly record)
+  #:use-module (srfi srfi-9)
+  #:export (define-record-type*))
+
+(define-syntax-rule (define-record-type* type
+                      constructor keyword-constructor
+                      predicate
+                      (field getter default) ...)
+  "Define a new, immutable record type named TYPE.  PREDICATE is the
+name of the procedure that tests if an object is of TYPE.  A GETTER is
+the name of the accessor for its respective FIELD.  CONSTRUCTOR is the
+name of the record type's low-level constructor that uses positional
+arguments corresponding to the order in which the fields are
+specified.  KEYWORD-CONSTRUCTOR is the name of the high-level
+constructor that uses keyword arguments for each FIELD whose values
+correspond to the DEFAULT associated with that field.  Additionally, a
+special keyword, #:inherit, can be used to copy values from another
+instance of TYPE and only change the fields that are explicitly
+overridden."
+  (begin
+    (define-record-type type
+      (constructor field ...)
+      predicate
+      (field getter) ...)
+
+    (define keyword-constructor
+      (let ((default-record (constructor default ...)))
+        (lambda* (#:key (inherit default-record)
+                        (field (getter inherit)) ...)
+          (constructor field ...))))))