Add iterate and macro-expand

d-.scm

@@ -1,15 +1,19 @@
 (define-module (d-)
   #:use-module (srfi srfi-1)
+  #:use-module (language tree-il)
   #:export
   (~>
    ~>>
+   as~>
    if-not
    when-not
    if-let
    for
    partial
    argmin
-   generator))
+   iterate
+   generator
+   macro-expand))
 
 (define-syntax ~>
   (syntax-rules ()
@@ -23,6 +27,13 @@
     [(~>> v (fn args ...) more ...) (~>> (fn args ... v) more ...)]
     [(~>> v fn more ...) (~>> (fn v) more ...)]))
 
+(define-syntax as~>
+  (syntax-rules ()
+    [(_ as v) v]
+    [(_ as v (fn args ...) more ...)
+     (let [(as v)]
+       (as~> as (fn args ...) more ...))]))
+
 (define-syntax-rule (if-not pred body ...)
   (if (not pred) body ...))
 
@@ -56,6 +67,11 @@
 	  #f
 	  vals))
 
+(define (iterate n f v)
+  (if (zero? n)
+      v
+      (iterate (1- n) f (f v))))
+
 ;; Shamelessly ripped from https://wingolog.org/archives/2013/02/25/on-generators
 (define (make-generator f)
   (define tag (make-prompt-tag))
@@ -76,3 +92,6 @@
 	 #'(make-generator
 	    (lambda (yield)
 	      expr ...)))])))
+
+;; Why wasn't this included?
+(define macro-expand (compose tree-il->scheme macroexpand))

test.scm

@@ -18,6 +18,14 @@
     (define value (~>> 1 (/ 2) (/ 2)))
     (assert-equal 1 value)))
 
+(define-test-suite "as~>"
+  (define-test "switch sides"
+    (define value (as~> % 'apples (cons % '()) (cons 'pears %)))
+    (assert-equal '(pears apples) value))
+  (define-test "middle argument"
+    (define value (as~> % '((apples . pears)) (assoc 'apples % equal?)))
+    (assert-equal '(apples .  pears) value)))
+
 (define-test-suite "if-not"
   (define-test "test"
     (assert-equal 'a (if-not #f 'a 'b))))
@@ -51,6 +59,11 @@
   (define-test "test"
     (assert-equal '(b . 2) (argmin cdr < '(a . 5) '(b . 2) '(c . 3)))))
 
+(define-test-suite "iterate"
+  (define-test "test"
+    (define value (iterate 2 1+ 3))
+    (assert-equal 5 value)))
+
 (define-test-suite "generator"
   (define-test "test"
     (define number-generator