adjust Instantiation syntax to lambdaeff

example/example.lua

@@ -1,7 +1,7 @@
 local eff = require('eff')
-local Eff, perform, handler = eff.Eff, eff.perform, eff.handler
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
 
-local Write = Eff("Write")
+local Write = inst()
 
 local test = function()
   local x = perform(Write("hello"))
@@ -24,15 +24,15 @@ function(k, arg)
   k()
 end)
 
-local Choice = Eff("Choice")
+local Choice = inst()
 
 local choiceh = handler(Choice,
 function(v) return v end,
 function(k, l, _)
   k(l)
 end)
 
-local Any = Eff("Any")
+local Any = inst()
 
 local anyh = handler(Any,
   function(v) print("anyh ended", v) return v end,

example/exception.lua

@@ -5,7 +5,7 @@ algebraic-exception for Lua
 local exn
 do
   local eff = require('eff')
-  local Eff, perform, handlers = eff.Eff, eff.perform, eff.handlers
+  local inst, perform, handlers = eff.inst, eff.perform, eff.handlers
 
   local handlers_ = function(...)
     local effeffhs = {...}
@@ -23,7 +23,7 @@ do
 
   exn = { raise = perform
         , handlers = handlers_
-        , Exception = Eff
+        , Exception = inst
         }
 end
 

example/monadic_pcall.lua

@@ -0,0 +1,27 @@
+local eff = require('eff')
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
+
+local Pcall = inst()
+local epcall = function(f, ...)
+  return perform(Pcall(f, ...))
+end
+
+local pcallh = handler(Pcall,
+  function(v) return v end,
+  function(k, f, ...)
+    local ok, content = pcall(f, ...)
+    if ok then
+      return k(content)
+    else -- error
+      return nil, content
+    end
+  end)
+
+pcallh(function()
+  local file = epcall(io.open, you_cannot_read, "r")
+  for l in file:lines() do
+    print(l)
+  end
+
+  file:close()
+end)

example/nilcheck.lua

@@ -0,0 +1,38 @@
+local eff = require('eff')
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
+
+local Fetch = inst()
+local fetch = function(it) return perform(Fetch(it)) end
+
+local Fallback = inst()
+
+local fetchh = handler(Fetch,
+  function(v) return v end,
+  function(k, it)
+    if it then
+      return k(it)
+    else
+      return k(perform(Fallback()))
+    end
+  end)
+
+local runfallback = function(default, th)
+  return handler(Fallback,
+    function(v) return v end,
+    function(k)
+      return k(default)
+    end)(th)
+end
+
+local t = {1, 2, 3}
+local u = {4, 5, 6}
+
+local result = runfallback(0, function()
+  return fetchh(function()
+    local x = fetch(t[3])
+    local y = fetch(u[4])
+    return x + y
+  end)
+end)
+
+print(result)

example/shiftreset.lua

@@ -1,12 +1,12 @@
 local eff = require("eff")
-local Eff, perform, handler = eff.Eff, eff.perform, eff.handler
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
 
 local inspect = require("inspect")
 
 local sr
 do
   local new_prompt = function()
-    local Shift0 = Eff("Shift0")
+    local Shift0 = inst()
 
     return {
       take = function(f) return perform(Shift0(f)) end,
@@ -84,7 +84,7 @@ print([[
 
 local promless
 do
-  local Shift0 = Eff("Shift0")
+  local Shift0 = inst()
 
   local shift0 = function(f)
     return perform(Shift0(f))

example/typeclass.lua

@@ -1,13 +1,13 @@
 local eff = require('eff')
-local Eff, perform, handler = eff.Eff, eff.perform, eff.handler
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
 
 print([[
 monoid
 =====]])
 
 do
-  local Empty = Eff("Empty")
-  local Concat = Eff("Concat")
+  local Empty = inst()
+  local Concat = inst()
 
   local empty = function()
     return perform(Empty())
@@ -81,7 +81,7 @@ fmap
 ===]])
 
 do
-  local Map = Eff("Map")
+  local Map = inst()
 
   local map = function(f, fa)
     return perform(Map(f, fa))

spec/async_await.lua

@@ -1,7 +1,7 @@
 -- https://github.com/ocamllabs/ocaml-effects-tutorial/blob/master/sources/solved/async_await.ml
 
 local eff = require('src/eff')
-local Eff, perform, handlers = eff.Eff, eff.perform, eff.handlers
+local inst, perform, handlers = eff.inst, eff.perform, eff.handlers
 
 local imut = require('spec/utils/imut')
 local ref = require('spec/utils/ref')
@@ -16,17 +16,17 @@ local Done = function(a)
   return { a, cls = "done" }
 end
 
-local Async = Eff("Async")
+local Async = inst()
 local async = function(f)
   return perform(Async(f))
 end
 
-local Yield = Eff("Yield")
+local Yield = inst()
 local yield = function()
   return perform(Yield())
 end
 
-local Await = Eff("Await")
+local Await = inst()
 local await = function(p)
   return perform(Await(p))
 end

spec/fringe.lua

@@ -1,9 +1,9 @@
 -- https://github.com/ocamllabs/ocaml-effects-tutorial/blob/master/sources/solved/fringe.ml
 
 local eff = require('src/eff')
-local Eff, perform, handler = eff.Eff, eff.perform, eff.handler
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
 
-local Yield = Eff("Yield")
+local Yield = inst()
 
 local generate = function(iter, c)
   local step = { f = nil }

spec/generator.lua

@@ -1,12 +1,12 @@
 -- https://github.com/ocamllabs/ocaml-effects-tutorial/blob/master/sources/solved/generator.ml
 
 local eff = require('src/eff')
-local Eff, perform, handler = eff.Eff, eff.perform, eff.handler
+local inst, perform, handler = eff.inst, eff.perform, eff.handler
 
 --[[
 iter : ('a table, 'a -> 'b) ->  ()
 --]]
-local Yield = Eff("Yield")
+local Yield = inst()
 
 local generate = function(iter, c)
   local step = { f = nil }

spec/state2.lua

@@ -1,14 +1,14 @@
 -- https://github.com/ocamllabs/ocaml-effects-tutorial/blob/master/sources/solved/state2.ml
 
 local eff = require('src/eff')
-local Eff, perform, handlers = eff.Eff, eff.perform, eff.handlers
+local inst, perform, handlers = eff.inst, eff.perform, eff.handlers
 
 local imut = require('spec/utils/imut')
 
 local State = function()
-  local Get = Eff("Get")
-  local Put = Eff("Put")
-  local History = Eff("History")
+  local Get = inst()
+  local Put = inst()
+  local History = inst()
 
   local get = function()
     return perform(Get())

src/eff.lua

@@ -9,7 +9,7 @@ local unpack = function(t)
   end
 end
 
-local Eff
+local inst
 do
   local __tostring = function(self)
     return tostring(self.eff)
@@ -18,9 +18,9 @@ do
   local v = {}
   v.cls = ("Eff: %s"):format(tostring(v):match('0x[0-f]+'))
 
-  Eff = setmetatable(v, {__call = function(self, eff)
+  inst = setmetatable(v, {__call = function(self)
     -- uniqnize
-    eff = ("%s: %s"):format(eff, tostring{}:match('0x[0-f]+'))
+    local eff = ("instance: %s"):format(tostring{}:match('0x[0-f]+'))
     local _Eff = setmetatable({eff = eff}, {__index = self})
 
     return setmetatable({--[[arg = nil]]}, {
@@ -62,7 +62,7 @@ do
 end
 
 local is_eff_obj = function(obj)
-  return type(obj) == "table" and (obj.cls == Eff.cls or obj.cls == Resend.cls)
+  return type(obj) == "table" and (obj.cls == inst.cls or obj.cls == Resend.cls)
 end
 
 local function get_effh(eff, effeffhs)
@@ -109,7 +109,7 @@ handler = function(eff, vh, effh)
         return vh(r)
       end
 
-      if r.cls == Eff.cls then
+      if r.cls == inst.cls then
         if is_the_eff(r.eff) then
           return effh(function(arg)
             return continue(gr, arg)
@@ -166,7 +166,7 @@ handlers = function(vh, ...)
         return vh(r)
       end
 
-      if r.cls == Eff.cls then
+      if r.cls == inst.cls then
         local effh = get_effh(r.eff, effeffhs)
         if effh then
           return effh(function(arg)
@@ -206,7 +206,7 @@ end
 
 
 return {
-  Eff = Eff,
+  inst = inst,
   perform = yield,
   handler = handler,
   handlers = handlers