diff --git a/config/schema.yml b/config/schema.yml
index 4c2d07a..5a07b27 100644
--- a/config/schema.yml
+++ b/config/schema.yml
@@ -293,6 +293,7 @@ properties:
                 properties:
                   color:
                     type: integer
+                    maximum: 0xffffff
                   alpha: &alpha
                     type: number
                     minimum: 0
@@ -311,6 +312,7 @@ properties:
                           maximum: 1
                         color:
                           type: integer
+                          maximum: 0xffffff
 
                   gradient_alpha:
                     type: array
diff --git a/src/color.lua b/src/color.lua
index bedbded..69a2b35 100644
--- a/src/color.lua
+++ b/src/color.lua
@@ -1,4 +1,5 @@
 local err = require 'err'
+local pure = require 'pure'
 
 --------------------------------------------------------------------------------
 -- colors
@@ -17,9 +18,7 @@ local rgba = function(hex, alpha)
    return err.set_type(obj, "color")
 end
 
-local rgb = function(hex)
-   return rgba(hex, 1.0)
-end
+local rgb = pure.partial(pure.flip(rgba), 1.0)
 
 --------------------------------------------------------------------------------
 -- Gradients
@@ -27,30 +26,35 @@ end
 -- these are tables like {[stop] :: color} where stop is a float between 0 and 1
 -- and color is a color as defined above
 
-local _make_gradient = function(colorstops, f)
-   local c = {}
-   for stop, spec in pairs(colorstops) do
-      assert(
-         stop <= 1 and stop >= 0,
-         "ERROR: color stop must be between 0 and 1; got " .. stop
-      )
-      c[stop] = f(spec)
-   end
-   return err.set_type(err.safe_table(c), "gradient")
+local _make_gradient = function(f)
+   return pure.compose(
+      pure.partial(pure.flip(err.set_type), "gradient"),
+      err.safe_table,
+      pure.array_to_map,
+      pure.partial(pure.kmap, function(stop, spec) return {stop, f(spec)} end)
+   )
 end
 
 -- {[stop] :: hex} -> Gradient
-local gradient_rgb = function(colorstops)
-   return _make_gradient(colorstops, rgb)
-end
+local gradient_rgb = _make_gradient(rgb)
 
 -- {[stop] :: {hex, alpha}} -> Gradient
-local gradient_rgba = function(colorstops)
-   return _make_gradient(
-      colorstops,
-      function(spec) return rgba(spec[1], spec[2]) end
-   )
-end
+local gradient_rgba = _make_gradient(function(spec) return rgba(spec[1], spec[2]) end)
+
+--------------------------------------------------------------------------------
+-- Yaml config to pattern tree
+
+local compile_gradient = pure.compose(
+   gradient_rgb,
+   pure.array_to_map,
+   pure.partial(pure.map, function(g) return {g.stop, g.color} end)
+)
+
+local compile_gradient_alpha = pure.compose(
+   gradient_rgba,
+   pure.array_to_map,
+   pure.partial(pure.map, function(g) return {g.stop, {g.color, g.alpha}} end)
+)
 
 local compile_patterns
 
@@ -62,21 +66,9 @@ compile_patterns = function(patterns)
       elseif v.color ~= nil then
          r[k] = rgba(v.color, v.alpha)
       elseif v.gradient ~= nil then
-         local p = {}
-         local g = v.gradient
-         for i = 1, #g do
-            local _g = g[i]
-            p[_g.stop] = _g.color
-         end
-         r[k] = gradient_rgb(p)
+         r[k] = compile_gradient(v.gradient)
       elseif v.gradient_alpha ~= nil then
-         local p = {}
-         local g = v.gradient_alpha
-         for i = 1, #g do
-            local _g = g[i]
-            p[_g.stop] = {_g.color, _g.alpha}
-         end
-         r[k] = gradient_rgba(p)
+         r[k] = compile_gradient_alpha(v.gradient_alpha)
       else
          r[k] = compile_patterns(v)
       end
diff --git a/src/pure.lua b/src/pure.lua
index 471f2c1..6c91ff9 100644
--- a/src/pure.lua
+++ b/src/pure.lua
@@ -77,6 +77,14 @@ M.imap = function(f, seq)
    return r
 end
 
+M.kmap = function(f, seq)
+   local r = {}
+   for k, v in pairs(seq) do
+      r[k] = f(k, v)
+   end
+   return r
+end
+
 M.map_keys = function(key, tbls)
    local r = {}
    for i = 1, #tbls do
@@ -119,8 +127,8 @@ end
 
 M.array_to_map = function(arr)
    local r = {}
-   for i = 1, #arr do
-      r[arr[i][1]] = arr[i][2]
+   for _, v in pairs(arr) do
+      r[v[1]] = v[2]
    end
    return r
 end