1 files changed, 53 insertions, 42 deletions
diff --git a/macros/core.fnl b/macros/core.fnl
index deb363a..9b01b70 100644
--- a/macros/core.fnl
+++ b/macros/core.fnl
@@ -50,50 +50,61 @@
              ,(_unpack body))))))
 
 
+(fn table-type [tbl]
+  (if (sequence? tbl) :seq
+      (table? tbl) :table
+      :else))
+
 ;; based on `seq' from `core.fnl'
 (fn into [to from]
-  (if (sequence? to)
-      `(let [to# ,to
-             from# ,from
-             insert# table.insert
-             unpack# (or table.unpack unpack)
-             res# []]
-         (var assoc# false)
-         (each [k# v# (pairs from#)]
-           (if (and (not assoc#)
-                    (not (= (type k#) "number")))
-               (set assoc# true))
-           (insert# res# [k# v#]))
-         (let [res# (if assoc# res# from#)]
-           (if (~= (next to#) nil)
-               (do (when (~= (next res#) nil)
-                     (each [_# v# (ipairs res#)]
-                       (insert# to# v#)))
-                   to#)
-               res#)))
-      ;; to support (into {} {}) we first need transform `from' into a
-      ;; sequential table.  Unfortunately it seems impossible to do
-      ;; this with `(into [] ,from)' call, as it results in infinity
-      ;; compilation loop.  Because of that the body of previous
-      ;; branch is repeated here almost entirely, although without
-      ;; some extra checks, as these aren't necessary in this case.
-      (table? to)
-      `(let [to# ,to
-             from# (let [from# ,from
-                         insert# table.insert
-                         unpack# (or table.unpack unpack)
-                         res# []]
-                     (var assoc# false)
-                     (each [k# v# (pairs from#)]
-                       (if (and (not assoc#)
-                                (not (= (type k#) "number")))
-                           (set assoc# true))
-                       (insert# res# [k# v#]))
-                     (if assoc# res# from#))]
-         (each [_# [k# v#] (ipairs from#)]
-           (tset to# k# v#))
-         to#)
-      `(error "expected table as the first argument" 2)))
+  (local to-type (table-type to))
+  (local from-type (table-type from))
+  `(let [to# ,to
+         from# ,from
+         insert# table.insert
+         table-type# (fn [tbl#]
+                       (let [t# (type tbl#)]
+                         (if (= t# :table)
+                             (let [(k# _#) (next tbl#)]
+                               (if (and (= (type k#) :number) (= k# 1)) :seq
+                                   (= k# nil) :empty
+                                   :table))
+                             :else)))
+         seq# (fn [tbl#]
+                (var assoc# false)
+                (let [res# []]
+                  (each [k# v# (pairs tbl#)]
+                    (if (and (not assoc#)
+                             (not (= (type k#) :number)))
+                        (set assoc# true))
+                    (insert# res# [k# v#]))
+                  (if assoc# res# tbl#)))
+         to-type# ,to-type
+         to-type# (if (= to-type# :else)
+                      (table-type# to#)
+                      to-type#)
+         from-type# ,from-type
+         from-type# (if (= from-type# :else)
+                        (table-type# from#)
+                        from-type#)]
+     (match to-type#
+       :seq (do (each [_# v# (ipairs (seq# from#))]
+                  (insert# to# v#)))
+       :table (match from-type#
+                :seq (each [_# [k# v#] (ipairs from#)]
+                       (tset to# k# v#))
+                :table (each [k# v# (pairs from#)]
+                         (tset to# k# v#))
+                :empty to#
+                :else (error "expected table as second argument"))
+       ;; If we could not deduce type, it means that
+       ;; we've got empty table.  We use will default
+       ;; to sequential table, because it will never
+       ;; break when converting into
+       :empty (do (each [_# v# (ipairs (seq# from#))]
+                    (insert# to# v#)))
+       :else (error "expected table as first argument"))
+     to#))
 
 {: if-let
  : when-let