Move internal modules to “internal” folder.

.internal/createCurry.js

@@ -0,0 +1,40 @@
+import apply from './.internal/apply.js';
+import createCtor from './.internal/createCtor.js';
+import createHybrid from './.internal/createHybrid.js';
+import createRecurry from './.internal/createRecurry.js';
+import getHolder from './.internal/getHolder.js';
+import replaceHolders from './.internal/replaceHolders.js';
+import root from './.internal/root.js';
+
+/**
+ * Creates a function that wraps `func` to enable currying.
+ *
+ * @private
+ * @param {Function} func The function to wrap.
+ * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
+ * @param {number} arity The arity of `func`.
+ * @returns {Function} Returns the new wrapped function.
+ */
+function createCurry(func, bitmask, arity) {
+  const Ctor = createCtor(func);
+
+  function wrapper(...args) {
+    let length = args.length;
+    const placeholder = getHolder(wrapper);
+    const holders = (length < 3 && args[0] !== placeholder && args[length - 1] !== placeholder)
+      ? []
+      : replaceHolders(args, placeholder);
+
+    length -= holders.length;
+    if (length < arity) {
+      return createRecurry(
+        func, bitmask, createHybrid, wrapper.placeholder, undefined,
+        args, holders, undefined, undefined, arity - length);
+    }
+    const fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
+    return apply(fn, this, args);
+  }
+  return wrapper;
+}
+
+export default createCurry;