From 1b2febbd13e597d7821e8f366c294c5371225472 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Tue, 28 Jun 2022 10:06:50 +0200
Subject: Add basic table.

---
 module/hnh/util/table.scm | 65 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 module/hnh/util/table.scm

diff --git a/module/hnh/util/table.scm b/module/hnh/util/table.scm
new file mode 100644
index 00000000..3afb3a46
--- /dev/null
+++ b/module/hnh/util/table.scm
@@ -0,0 +1,65 @@
+(define-module (hnh util table)
+  :use-module (srfi srfi-1)
+  :use-module (srfi srfi-88)
+  :use-module (srfi srfi-9)
+  :use-module (srfi srfi-9 gnu)
+  :use-module (hnh util lens)
+  :use-module (hnh util object)
+  :export ((make-tree . table)
+           (tree-get . table-get)
+           (tree-put . table-put)
+           (tree? . table?)
+           (alist->tree . alist->table)))
+
+(define (symbol<? . args)
+  (apply string<? (map symbol->string args)))
+
+(define-syntax-rule (symbol< args ...)
+  (string< (symbol->string args) ...))
+
+(define-type (tree-node)
+  (key type: symbol?)
+  value
+  (left type: tree? default: (tree-terminal))
+  (right type: tree? default: (tree-terminal)))
+
+;; Type tagged null
+(define-type (tree-terminal))
+
+;; Wrapped for better error messages
+(define (make-tree) (tree-terminal))
+
+(define (tree? x)
+  (or (tree-node? x)
+      (tree-terminal? x)))
+
+(define (tree-put tree k v)
+  (cond ((tree-terminal? tree) (tree-node key: k value: v))
+        ((eq? k (key tree)) (value tree v))
+        (else
+         (modify tree (if (symbol<? k (key tree)) left right)
+                 tree-put k v))))
+
+(define (tree-get tree k)
+  (cond ((tree-terminal? tree) (throw 'out-of-range))
+        ((eq? k (key tree)) (value tree))
+        ((symbol<? k (key tree))
+         (tree-get (left tree) k))
+        (else
+         (tree-get (right tree) k))))
+
+
+(define (alist->tree alist)
+  (fold (lambda (kv tree) (apply tree-put tree kv))
+        (tree-terminal)
+        alist))
+
+
+
+(define (make-indent depth) (make-string (* 2 depth) #\space))
+
+(define* (print-tree tree optional: (depth 0))
+  (unless (tree-terminal? tree)
+    (format #t "~a- ~s: ~s~%" (make-indent depth) (key tree) (value tree))
+    (print-tree (left tree) (1+ depth))
+    (print-tree (right tree) (1+ depth))))
-- 
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