havenwood · November 6, 2017 23:42 · Nov 6, 2017 · Nov 6, 2017 · Nov 6, 2017 · Nov 6, 2017
diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -83,6 +83,12 @@ def fmap(*args)
   end
 end
 
+def const(*args)
+  -> (val) {
+    -> (_) { val }
+  }.curry[*args]
+end
+
 module L
   class << self
     def ens(*args)
@@ -106,6 +112,12 @@ def view(*args)
         lens.(Const.make).(obj).value
       }.curry[*args]
     end
+
+    def set(*args)
+      -> (lens, val, obj) {
+        over(lens, const(val), obj)
+      }.curry[*args]
+    end
   end
 end
 
@@ -158,6 +170,12 @@ def self.lens_path(*args)
   profile
 )
 
+puts L.set(
+  ability_l,
+  'composing functions',
+  profile
+)
+
 puts L.over(
   ability_l,
   upcase,

diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -103,7 +103,7 @@ def over(*args)
 
     def view(*args)
       -> (lens, obj) {
-        lens.(Const.make, obj).value
+        lens.(Const.make).(obj).value
       }.curry[*args]
     end
   end
@@ -149,16 +149,23 @@ def self.lens_path(*args)
   }
 }
 
-friend_ability_l = Hash.lens_path([:friend, :details, :ability])
+friend_l = Hash.lens_path([:friend])
+ability_l = Hash.lens_path([:details, :ability])
 upcase = -> (e) { e.upcase }
 
 puts L.view(
-  friend_ability_l,
+  friend_l * ability_l,
   profile
 )
 
 puts L.over(
-  friend_ability_l,
+  ability_l,
+  upcase,
+  profile
+)
+
+puts L.over(
+  friend_l * ability_l,
   upcase,
   profile
 )
diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -149,12 +149,11 @@ def self.lens_path(*args)
   }
 }
 
-friend_l = Hash.lens_path([:friend])
-ability_l = Hash.lens_path([:details, :ability])
+friend_ability_l = Hash.lens_path([:friend, :details, :ability])
 upcase = -> (e) { e.upcase }
 
 puts L.view(
-  friend_l * ability_l,
+  friend_ability_l,
   profile
 )
 

diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -41,7 +41,7 @@ def deep_dup
 
 class Proc
   def *(other)
-    -> (*args) { self[other[args]] }
+    -> (*args) { self[other[*args]] }
   end
 end
 
@@ -138,6 +138,9 @@ def self.lens_path(*args)
 
 profile = {
   username: 'dminuoso',
+  details: {
+    ability: 'writing functions',
+  },
   friend: {
     name: 'baweaver',
     details: {
@@ -146,11 +149,12 @@ def self.lens_path(*args)
   }
 }
 
-friend_ability_l = Hash.lens_path([:friend, :details, :ability])
+friend_l = Hash.lens_path([:friend])
+ability_l = Hash.lens_path([:details, :ability])
 upcase = -> (e) { e.upcase }
 
 puts L.view(
-  friend_ability_l,
+  friend_l * ability_l,
   profile
 )
 

diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -70,7 +70,7 @@ def self.lens_index(*args)
 
   def self.update(*args)
     -> (n, v, array) {
-      array[n] = v
+      array.deep_dup.tap { |a| a[n] = v }
     }.curry[*args]
   end
 end

diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -50,9 +50,10 @@ def deep_dup
     map(&:deep_dup)
   end
 
-  def fmap(func = nil, &blk)
-    f = func || blk
-    map(&f)
+  def fmap(*args)
+    -> (fun, e) {
+      e.map(&fun)
+    }.curry[*args]
   end
 
   def self.nth(*args)
@@ -76,7 +77,9 @@ def self.update(*args)
 
 module Kernel
   def fmap(*args)
-    -> (fn, e) { e.class.instance_method(:fmap).bind(e).call(fn) }.curry[*args]
+    -> (fn, e) {
+      e.class.instance_method(:fmap).bind(e).call(fn)
+    }.curry[*args]
   end
 end
 
@@ -133,7 +136,6 @@ def self.lens_path(*args)
   end
 end
 
-
 profile = {
   username: 'dminuoso',
   friend: {

diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -35,7 +35,7 @@ def deep_dup
         hash[key.deep_dup] = value.deep_dup
       end
     end
-		hash
+    hash
   end
 end
 
@@ -135,13 +135,13 @@ def self.lens_path(*args)
 
 
 profile = {
-	username: 'dminuoso',
-	friend: {
-		name: 'baweaver',
-		details: {
-			ability: 'puns',
-		}
-	}
+  username: 'dminuoso',
+  friend: {
+    name: 'baweaver',
+    details: {
+      ability: 'puns',
+    }
+  }
 }
 
 friend_ability_l = Hash.lens_path([:friend, :details, :ability])
@@ -153,7 +153,7 @@ def self.lens_path(*args)
 )
 
 puts L.over(
-	friend_ability_l,
+  friend_ability_l,
   upcase,
   profile
 )
diff --git a/van_laarhoven_lens.rb b/van_laarhoven_lens.rb
@@ -0,0 +1,159 @@
+# Identity functor that does not give any additional structure
+Identity = Struct.new(:value) do
+  def fmap(func = nil, &blk)
+    f = func || blk;
+    Identity.new(f.call(self.value))
+  end
+end
+
+# Const Functor that preserves its content
+Const = Struct.new(:value) do
+  def fmap(f = nil, o = nil)
+    self
+  end
+
+  # A curried constructor for sanity.
+  def self.make(*args)
+    -> (o) { new(o) }.curry[*args]
+  end
+end
+
+class Object
+  def deep_dup
+    dup
+  end
+end
+
+class Hash
+  def deep_dup
+    hash = dup
+    each_pair do |key, value|
+      if key.frozen? && ::String === key
+        hash[key] = value.deep_dup
+      else
+        hash.delete(key)
+        hash[key.deep_dup] = value.deep_dup
+      end
+    end
+		hash
+  end
+end
+
+class Proc
+  def *(other)
+    -> (*args) { self[other[args]] }
+  end
+end
+
+class Array
+  def deep_dup
+    map(&:deep_dup)
+  end
+
+  def fmap(func = nil, &blk)
+    f = func || blk
+    map(&f)
+  end
+
+  def self.nth(*args)
+    -> (n) {
+      -> (o) { o[n] }
+    }.curry[*args]
+  end
+
+  def self.lens_index(*args)
+    -> (n) {
+      L.ens(nth(n), update(n))
+    }.curry[*args]
+  end
+
+  def self.update(*args)
+    -> (n, v, array) {
+      array[n] = v
+    }.curry[*args]
+  end
+end
+
+module Kernel
+  def fmap(*args)
+    -> (fn, e) { e.class.instance_method(:fmap).bind(e).call(fn) }.curry[*args]
+  end
+end
+
+module L
+  class << self
+    def ens(*args)
+      -> (g, s, w, t) {
+        fmap(-> (f) {
+          s.(f, t)
+        }, w.(g.(t)))
+      }.curry[*args]
+    end
+
+    def over(*args)
+      -> (lens, fun, obj) {
+        lens.(-> (y) {
+          Identity.new(fun.(y))
+        }).(obj).value
+      }.curry[*args]
+    end
+
+    def view(*args)
+      -> (lens, obj) {
+        lens.(Const.make, obj).value
+      }.curry[*args]
+    end
+  end
+end
+
+class Hash
+  def self.getter(*args)
+    -> (paths, obj) {
+      obj.dig(*paths)
+    }.curry[*args]
+  end
+
+  def self.setter(*args)
+    -> (paths, val, obj) {
+      obj.deep_dup.tap do |o|
+        *dir, final = paths
+        if dir.empty?
+          o.store(final, val)
+        else
+          o.dig(*dir).store(final, val)
+        end
+      end
+    }.curry[*args]
+  end
+
+  def self.lens_path(*args)
+    -> (paths) {
+      L.ens(getter(paths), setter(paths))
+    }.curry[*args]
+  end
+end
+
+
+profile = {
+	username: 'dminuoso',
+	friend: {
+		name: 'baweaver',
+		details: {
+			ability: 'puns',
+		}
+	}
+}
+
+friend_ability_l = Hash.lens_path([:friend, :details, :ability])
+upcase = -> (e) { e.upcase }
+
+puts L.view(
+  friend_ability_l,
+  profile
+)
+
+puts L.over(
+	friend_ability_l,
+  upcase,
+  profile
+)