From 2754eae6d0c66b2838dc7566904d920ce216dddc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@hornquist.se>
Date: Sat, 10 Nov 2018 18:43:54 +0100
Subject: Fixed up examples.

---
 data/optional.scm |  9 ++-------
 data/writer.scm   |  5 ++++-
 examples.scm      | 45 ++++++++++-----------------------------------
 3 files changed, 16 insertions(+), 43 deletions(-)

diff --git a/data/optional.scm b/data/optional.scm
index a1968f0..e71c10d 100644
--- a/data/optional.scm
+++ b/data/optional.scm
@@ -5,8 +5,8 @@
   #:export (nothing just
                     nothing? just?
                     return-optional)
-  #:re-export (>>=)
-  )
+  ;; TODO is this reexport needed?
+  #:re-export (>>=))
 
 (define-class <optional> ()
   (slot #:init-value #f
@@ -40,8 +40,3 @@
         ((just? this) 
          (match this
            (($ <optional> slot) (proc slot))))))
-
-#;
-(define-method (mappend (a <optional>) (b <optional>))
-  (match a
-    (($ ))))
diff --git a/data/writer.scm b/data/writer.scm
index b79c670..462d391 100644
--- a/data/writer.scm
+++ b/data/writer.scm
@@ -3,7 +3,7 @@
   #:use-module (ice-9 match)
   #:use-module (data monoid)
   #:use-module (control monad)
-  #:export (writer))
+  #:export (writer return-writer))
 
 (read-enable 'curly-infix)
 
@@ -23,6 +23,9 @@
                  (($ <writer> nval ncontext)
                   (writer nval { monoid <> ", " <> ncontext }))))))
 
+(define (return-writer val)
+  (writer val ""))
+
 (define-method (write (this <writer>) port)
   (match this (($ <writer> value monoid)
                (format port "[Writer ~s, ~s]" value monoid))))
diff --git a/examples.scm b/examples.scm
index a2f2319..3b67f60 100644
--- a/examples.scm
+++ b/examples.scm
@@ -10,52 +10,27 @@
              (data optional)
              (data writer))
 
-(do (just x) <- (just 10)
+(do x <- (just 10)
     x) ; => 10
 
 (do let y = (just 10)
-    (just x) <- y
+    x <- y
     (+ x 5)) ; => 15
 
-(do (just x) <- (nothing)
+(do x <- (nothing)
     (+ x 5)) ; => [Nothing]
 
-;;;
+(do x <- (just 10)
+    y <- (just 20)
+    (+ x y)) ; => 30
 
-(do let either = left 10
-    (left x) <- either
-    x) ; EVALUATION ERROR
+;;;
 
 ;; Int -> Writer Int String
 (define (log-number n)
   (writer n (format #f "Got nuber: ~a" n)))
 
-(define (mult-with-log)
-  (do (writer a) <- (log-number 3)
-      (writer b) <- (log-number 5)
-      (* a b)))
-
-(do (writer a) <- (log-number 1)
-    a) ; EVALUATION ERROR
-
-(begin { (log-number 1) >>= log-number })
-;; => [Writer 1, "Got nuber: 1, Got nuber: 1"]
-
-(do (writer a) <- (log-number 3)
-    (writer b) <- (log-number 5)
+(do a <- (log-number 3)
+    b <- (log-number 5)
     (writer (* a b) ""))
-;; EVALUATION ERROR
-;; => [Writer 3, "Got nuber: 3, base"]
-
-(log-number 3) ; => [Writer 3, "Got nuber: 3"]
-(just 1) ; => [Just 1]
-
-(do let y = 5
-    (just x) <- (just 10)
-    (just (* x y)))
-;; => [Just 50]
-
-;;; TODO
-;;; '<- and 'let can't be used after '<-
-
-
+;; => [Writer 15, "Got nuber: 3, Got nuber: 5, "]
-- 
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