diff --git a/jekyll.el b/jekyll.el
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new mode 100644
diff --git a/tools.el b/tools.el
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+;;
+;; Various tool functions & macros
+;;
+
+(defmacro comment (&rest body)
+  "Ignores body, yields nil"
+  nil)
+
+;;;;;;;
+;; Math
+
+(defun mean (values)
+  (/ (reduce '+ values)
+     (float (length values))))
+
+(defun square (x)
+  (* x x))
+
+(defun variance (values)
+  (- (->> values (mapcar 'square) mean)
+     (square (mean values))))
+
+;;;;;;;;;;;;
+;; Sequences
+
+(defun sequence (maybe-seq)
+  "Returns the value wrapped in a sequence if it is not a sequence already."
+  (if (sequencep maybe-seq) maybe-seq
+    (list maybe-seq)))
+
+(defun random-elt (sequence)
+  (elt sequence
+       (-> sequence length random)))
+
+(defun seq-difference (lseq rseq)
+  (remove-if (lambda (element) (find element rseq :test 'equal))
+             lseq))
+
+;;;;;;;;;;
+;; Strings
+
+(defun string-empty-p (str)
+  (unless (stringp str)
+    (error "not a string."))
+  (string= "" str))
+
+(defun string-not-blank-p (str)
+  (when str
+    (not (string-empty-p str))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Undestructive alist functions
+
+(defun alist-get (alist key &optional default)
+  (or (assoc-default key alist)
+      default))
+
+(defun alist-remove (alist key)
+  "Doesn't change the original alist, returns a new one instead."
+  (remove-if (lambda (x) (equal key (car x)))
+             alist))
+
+(defun alist-set (alist key value)
+  "Doesn't change the original alist, returns a new one instead."
+  (cons (cons key value) (alist-remove alist key)))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Clojure's Trush operators
+
+(defmacro -> (result &rest body)
+  (dolist (form body result)
+    (setq form (sequence form)
+          result (append (list (car form) result)
+                         (cdr form)))))
+
+(defmacro ->> (result &rest body)
+  (dolist (form body result)
+    (setq form (sequence form)
+          result (append form (list result)))))
+
+;;;;;;;;;;;;;;;;;;;;
+;; Functional tools
+
+(defmacro partial (f &rest args)
+  `(lambda (&rest more)
+     (apply ',f ,@args more)))
+
+(defmacro lexdef (name args &rest body)
+  "Defun with lexically-scoped parameters. Could also be called lexical-defun."
+  `(defun ,name ,args
+     (lexical-let ,(->> args
+                        (remove-if (partial equal '&rest))
+                        (mapcar (lambda (arg) (list arg arg))))
+       ,@body)))
+
+(provide 'tools)
diff --git a/tools.elk b/tools.elk
new file mode 100644
index 0000000..096a992
--- /dev/null
+++ b/tools.elk
@@ -0,0 +1,130 @@
+;;
+;;
+;;
+
+(require 'tools)
+
+(deftest "seq returns the sequence itself"
+  (assert-equal '(1)
+                (seq '(1)))
+  (assert-equal [1]
+                (seq [1]))
+  (assert-equal "1"
+                (seq "1")))
+
+(deftest "seq turns non-sequences into a list"
+  (assert-equal '(1)
+                (seq 1))
+  (assert-equal '(toto)
+                (seq 'toto)))
+
+(deftest "currying the plus function"
+  (assert-equal 5
+                (funcall (partial + 2) 3)))
+
+(deftest "using curry in map"
+  (assert-equal  [2 4 6]
+                (map 'vector (partial * 2) [1 2 3])))
+
+(deftest "using curry in filter"
+  (assert-equal [2 3]
+                (remove-if-not (partial < 1) [1 2 3])))
+
+(deftest "applying trush to one form"
+  (assert-equal 5.0
+                (-> 25 sqrt)))
+
+(deftest "applying trush to two forms"
+  (assert-equal 3.0
+                (-> 25 sqrt (- 2))))
+
+(deftest "chaining trush combinators"
+  (assert-equal "-2.0"
+                (-> 25 sqrt (->> (- 3) number-to-string))))
+
+(deftest "threading three forms"
+  (assert-equal '(* 6 (+ 4 5 (- 2 3 x)))
+                (macroexpand '(->> x (- 2 3) (+ 4 5) (* 6)))))
+
+(lexdef lexdef-test (x)
+        (lambda () x))
+
+(defun defun-test (x)
+  (lambda () x))
+
+(deftest "lexdef has lexical scoping"
+  (let ((lexical (lexdef-test 1))
+        (dynamic (defun-test 1))
+        (x 2))
+    (assert-equal 1
+                  (funcall lexical))
+    (assert-equal 2
+                  (funcall dynamic))))
+
+(deftest "comment returns nil"
+  (assert-equal nil
+                (comment 3)))
+
+(deftest "comment does nothing"
+  (let ((x 1))
+    (setq x 2)
+    (comment
+     (setq x 3))
+    (assert-equal 2 x)))
+
+(deftest "variance of a const list returns 0"
+  (->> [[1 1 1]
+        [2 2 2 2 2]
+        [3 3 3 3 3 3 3]]
+       (mapcar (lambda (v)
+                 (assert-equal 0.0 (variance v))))))
+
+(deftest "variance of a simple list"
+  (assert-that (lambda (x) (< (eval x) 0.001))
+               (- (/ 2 3.0)
+                  (variance [1 2 3]))))
+
+(deftest "retrieving a random element"
+  (assert-equal "ABC"
+                (random-elt ["ABC"])))
+
+(deftest "I can substract two vectors"
+  (assert-equal ["ABC"]
+                (seq-difference ["ABC" "DEF"] ["DEF"])))
+
+;;;
+;; Alist functions
+
+(deftest "I can get a value by key in an alist"
+  (let ((h '((a . 1)(b . 2))))
+    (assert-equal 1
+                  (alist-get h 'a))
+    (assert-equal 2
+                  (alist-get h 'b))
+    (assert-nil (alist-get h 'z))
+    (assert-equal 26
+                  (alist-get h 'z 26))))
+
+(deftest "I can remove a value in an alist"
+  (let ((h '((a . 1)(b . 2)(a . 3))))
+    (assert-nil (-> h (alist-remove 'a) (alist-get 'a)))))
+
+(deftest "I can set a value in an alist"
+  (let ((h '((a . 1)(b . 2)(a . 3))))
+    (assert-equal '((a . 5)(b . 2)) (-> h (alist-set 'a 5)))
+    (assert-equal '((a . 1)(b . 2)(a . 3)) h)))
+
+;;;;;;;;;;
+;; Strings
+
+(deftest "an empty string is empty, a non empty string is not empty"
+  (assert-nil (string-empty-p "hello"))
+  (assert-nonnil (string-empty-p (copy-seq "")))
+  (assert-error "string" (string-empty-p 1))
+  (assert-error "string" (string-empty-p nil)))
+
+(deftest "I can tell if a sring is blank"
+  (assert-t (string-not-blank-p "hello"))
+  (assert-nil (string-not-blank-p nil))
+  (assert-nil (string-not-blank-p ""))
+  (assert-error "string" (string-not-blank-p 1)))