1 files changed, 145 insertions, 0 deletions
diff --git a/examples/lexpr.pd_lua b/examples/lexpr.pd_lua
new file mode 100644
index 0000000..487c87e
--- /dev/null
+++ b/examples/lexpr.pd_lua
@@ -0,0 +1,145 @@
+local lexpr = pd.Class:new():register("lexpr")
+
+local function sandbox(e, f) -- only supports nullary f() with one return
+  local g = getfenv(f)
+  setfenv(f, e)
+  local r = f()
+  setfenv(f, g)
+  return r
+end
+
+local lexpr_globals = {
+  abs    = math.abs,
+  acos   = math.acos,
+  asin   = math.asin,
+  atan   = math.atan,
+  atan2  = math.atan2,
+  ceil   = math.ceil,
+  cos    = math.cos,
+  cosh   = math.cosh,
+  deg    = math.deg,
+  exp    = math.exp,
+  floor  = math.floor,
+  fmod   = math.fmod,
+  log    = math.log,
+  log10  = math.log10,
+  max    = math.max,
+  min    = math.min,
+  int    = function (x) i,f = math.modf(x) ; return i end,
+  wrap   = function (x) i,f = math.modf(x) ; return f end,
+  pi     = math.pi,
+  pow    = math.pow,
+  rad    = math.rad,
+  sin    = math.sin,
+  sinh   = math.sinh,
+  sqrt   = math.sqrt,
+  tan    = math.tan,
+  tanh   = math.tanh,
+  val    = function (s) return (pd.getvalue(s) or 0) end,
+  choose = function (b,t,f) if b then return t else return f end end
+}
+
+function lexpr:readexpr(atoms)
+  local vname = { }
+  local context = { }
+  local expr
+  local i
+  local k
+  local v
+  local j = 1
+  local inlets
+  local f
+  local phase = "vars"
+  for k,v in pairs(lexpr_globals) do
+    context[k] = v
+  end
+  for i,v in ipairs(atoms) do
+    if phase == "vars" then        -- create variables
+      if v == "->" then
+        inlets = i - 1
+        phase = "expr"
+        expr = ""
+      else
+        if type(v) == "string" then
+          vname[j] = v
+          context[v] = 0
+          j = j + 1
+        else
+          self:error("lexpr: variable names must be symbols")
+          return -1
+        end
+      end
+    else if phase == "expr" then  -- build string
+      expr = expr .. " " .. v
+    else
+      self:error("lexpr: internal error parsing expression")
+      return -1
+    end end
+  end
+  f = assert(loadstring("return {" .. expr .. " }"))
+  local outlets = #(sandbox(context, f))
+  return inlets, vname, context, f, outlets
+end
+
+function lexpr:initialize(sel, atoms)
+  self.vname = { }
+  self.context = { }
+  self.hot = { }
+  self.f = function () return 0 end
+  function self:in_1_bang()
+    local r = sandbox(self.context, self.f)
+    local i
+    for i = self.outlets,1,-1 do
+      if type(r[i]) == "number" then
+        self:outlet(i, "float", { r[i] })
+      else if type(r[i]) == "string" then
+        self:outlet(i, "symbol", { r[i] })
+      else
+        self:error("calculated a " .. type(r[i]) .. " but expected a number or a string")
+      end end
+    end
+  end
+  function self:in_n_float(i, f)
+    self.context[self.vname[i]] = f
+    if self.hot[i] then self:in_1_bang() end
+  end
+  function self:in_n_symbol(i, s)
+    self.context[self.vname[i]] = s
+    if self.hot[i] then self:in_1_bang() end
+  end
+  function self:in_n_hot(i, atoms)
+    if type(atoms[1]) == "number" then
+      self.hot[i] = atoms[1] ~= 0
+    else
+      self:error("hot method expects a float")
+    end
+  end
+  function self:in_1_lexpr(atoms)
+    local inlets
+    local vname
+    local context
+    local f
+    local outlets
+    inlets, vname, context, f, outlets = self:readexpr(atoms)
+    if (inlets == self.inlets) and (outlets == self.outlets) then
+      self.vname = vname
+      self.context = context
+      self.f = f
+    else
+      self:error("new expression has different inlet/outlet count")
+    end
+  end
+  self.inlets, self.vname, self.context, self.f, self.outlets = self:readexpr(atoms)
+  if self.inlets < 1 then
+    pd.post("lexpr: error: would have no inlets")
+    return false
+  end
+  if self.outlets < 1 then
+    pd.post("lexpr: error: would have no outlets")
+    return false
+  end
+  for i = 1,self.inlets,1 do
+    self.hot[i] = i == 1
+  end
+  return true
+end