From 049c352ea84e9ea6e1df2236d15a1b63e12d9e84 Mon Sep 17 00:00:00 2001
From: Helmut Merz <helmutm@cy55.de>
Date: Thu, 22 May 2025 11:49:24 +0200
Subject: [PATCH] provide tensor function, just creating arrays

---
 decons.lisp      | 20 ++++++++++++++++++--
 test-decons.lisp | 12 ++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/decons.lisp b/decons.lisp
index 58c2409..f6eb901 100644
--- a/decons.lisp
+++ b/decons.lisp
@@ -3,9 +3,9 @@
 (defpackage :decons
   (:use :common-lisp)
   (:local-nicknames (:util :scopes/util))
-  (:export #:*pi*
-           #:area #:circle
+  (:export #:*pi* #:area #:circle
            #:absv #:double #:remainder
+           #:scalar-p #:tensor #:at
            #:line
            ))
 
@@ -34,6 +34,22 @@
     v
     (remainder (- v d) d)))
 
+;;;; library stuff
+
+(defgeneric scalar-p (x)
+  (:method (x) t)
+  (:method ((x list)) nil)
+  (:method ((x array)) nil))
+
+(defun tensor (s v)
+  (make-array s :initial-contents v))
+
+(defun at (a &rest subs)
+  (apply #'aref a subs))
+
+(defun (setf at) (v a &rest subs)
+  (setf (apply #'aref a subs) v))
+
 ;;;; parameterized functions
 
 (defun line (x)
diff --git a/test-decons.lisp b/test-decons.lisp
index 89cfaee..e2099f8 100644
--- a/test-decons.lisp
+++ b/test-decons.lisp
@@ -11,6 +11,7 @@
 (defun run ()
   (let ((t:*test-suite* (t:test-suite "decons")))
     (test-basic)
+    (test-lib)
     (test-line)
     (t:show-result)))
 
@@ -24,6 +25,17 @@
   (== (decons:remainder 7 4) 3)
 )
 
+(deftest test-lib ()
+  (== (decons:scalar-p 7) t)
+  (== (decons:scalar-p '(a b)) nil)
+  (let ((t1 (decons:tensor '(4) '(0 1 2 3))))
+    (== (decons:at t1 0) 0)
+    (setf (decons:at t1 0) 5)
+    (== (decons:at t1 0) 5)
+    (== (decons:scalar-p t1) nil)
+    )
+)
+
 (deftest test-line ()
   (let ((p1 (decons:line 0.0))
         (p2 (decons:line 1.0))