From 4c31b0b94489156a2228cf53a2175719f9aacf0b Mon Sep 17 00:00:00 2001
From: fiddlerwoaroof <fiddlerwoaroof@gmail.com>
Date: Sun, 13 Aug 2017 12:49:23 -0700
Subject: [PATCH] Initial commit

---
 .gitignore    |  1 +
 data-lens.asd |  8 ++++++
 lens.lisp     | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 data-lens.asd
 create mode 100644 lens.lisp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..be303db
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.fasl
diff --git a/data-lens.asd b/data-lens.asd
new file mode 100644
index 0000000..8cfad8c
--- /dev/null
+++ b/data-lens.asd
@@ -0,0 +1,8 @@
+(asdf:defsystem #:data-lens
+  :description "Utilities for building data transormations from composable functions, modeled on lenses and transducers"
+  :author "Edward Langley <edward@elangley.org>"
+  :license "MIT"
+  :depends-on (cl-ppcre)
+  :serial t
+  :components ((:file "lens")))
+
diff --git a/lens.lisp b/lens.lisp
new file mode 100644
index 0000000..3cdc0f9
--- /dev/null
+++ b/lens.lisp
@@ -0,0 +1,75 @@
+(defpackage :data-lens
+  (:use :cl)
+  (:export #:regex-match #:include #:exclude #:pick
+           #:snapshot-to-vector #:vector-to-lt #:key-transform
+           #:combine #:derive #:cumsum #:over #:on #:shortcut
+           #:defun-ct))
+(in-package :data-lens)
+
+(defmacro shortcut (name function &body bound-args)
+  `(eval-when (:load-toplevel :compile-toplevel :execute)
+     (setf (fdefinition ',name)
+           (,function ,@bound-args))))
+
+(defmacro defun-ct (name (&rest args) &body body)
+  `(eval-when (:load-toplevel :compile-toplevel :execute)
+     (defun ,name ,args
+       ,@body)))
+
+(defun-ct regex-match (regex)
+  (lambda (data)
+    (cl-ppcre:scan-to-strings regex data)))
+
+(defun-ct include (pred)
+  (lambda (seq)
+    (remove-if-not pred seq)))
+
+(defun-ct exclude (pred)
+  (lambda (seq)
+    (remove-if pred seq)))
+
+(defun-ct pick (selector)
+  (lambda (seq)
+    (map 'list selector seq)))
+
+(defun-ct key-transform (fun key-get key-set)
+  (lambda (it)
+    (let ((key-val (funcall key-get it)))
+      (funcall key-set
+               (funcall fun key-val)))))
+
+(defun-ct combine (fun1 fun2)
+  (lambda (item)
+    (list (funcall fun1 item)
+          (funcall fun2 item))))
+
+(defun-ct derive (diff-fun &key (key #'identity))
+  (lambda (list)
+    (mapcar (lambda (next cur)
+              (cons (funcall diff-fun (funcall key next) (funcall key  cur))
+                    next))
+            (cdr list)
+            list)))
+
+(defun-ct cumsum (&key (add-fun #'+) (key #'identity) (combine (lambda (x y) y x)) (zero 0))
+  (lambda (seq)
+    (nreverse
+     (reduce (lambda (accum next)
+               (let ((key-val (funcall key next))
+                     (old-val (if accum
+                                  (funcall key (car accum))
+                                  zero)))
+                 (cons (funcall combine
+                                (funcall add-fun old-val key-val)
+                                next)
+                       accum)))
+             seq
+             :initial-value ()))))
+
+(defun-ct over (fun &key (result-type 'list))
+  (lambda (seq)
+    (map result-type fun seq)))
+
+(defun-ct on (fun key)
+  (lambda (it)
+    (funcall fun (funcall key it))))