From 26ffc303a04341c05d0eee87d4fc9089e40018a3 Mon Sep 17 00:00:00 2001
From: Viliam Vadocz <viliam.vadocz@gmail.com>
Date: Mon, 6 Apr 2020 20:01:55 +0200
Subject: [PATCH] Reverse iteration (#13)

* first version of reverse iteration

* No significant changes
---
 examples/test.vlp  | 16 +---------------
 volpe/builder.py   | 33 +++++++++++++++++++++++++--------
 volpe/compile.py   | 10 +++++-----
 volpe/run_volpe.py |  2 +-
 4 files changed, 32 insertions(+), 29 deletions(-)

diff --git a/examples/test.vlp b/examples/test.vlp
index d525def..4e2cca1 100644
--- a/examples/test.vlp
+++ b/examples/test.vlp
@@ -1,15 +1 @@
-f = (x, [y, z]) => [&x..10, y..z]
-a = f(0, [0, 10])
-[b, c] = a
- 
-# functions
-# :> f
-
-# tuples
-# :> [1 > 0, [1, 0.0], f, b, c]
-
-# iterators
-# :> c :: i => [i, i.0, f, f(i-5, [0, 2])]
-
-# lists
-:> b
+:> [&0..5, &5..0, &3..5, &5..3, &0..0, &0..1, &1..0, &-20..-5]
\ No newline at end of file
diff --git a/volpe/builder.py b/volpe/builder.py
index 037dfd7..353b9a9 100644
--- a/volpe/builder.py
+++ b/volpe/builder.py
@@ -109,16 +109,33 @@ def number_iter(self, tree: TypeTree):
         module = self.builder.module
         env_types = [int32]
 
-        with build_closure(module, closure_type, env_types) as (b, args, closure, c_func):
-            start = read_environment(b, args[0], env_types)[0]
-            b.ret(b.add(start, args[1]))
+        # TODO compact or simplify the following code:
 
-        # TODO going in reverse
+        with options(self.builder, tree.return_type) as (ret, phi):
+            # reverse = a > b in (a..b).
+            reverse = self.builder.icmp_signed(">", values[0], values[1])
+            with self.builder.if_then(reverse):
+                # Going in reverse (10..0).
+                with build_closure(module, closure_type, env_types) as (b, args, closure, c_func):
+                    start = read_environment(b, args[0], env_types)[0]
+                    b.ret(b.sub(start, b.add(args[1], int32(1))))
+
+                env_ptr = write_environment(self.builder, [values[0]])
+                list_value = tree.return_type(ir.Undefined)
+                list_value = self.builder.insert_value(list_value, self.builder.insert_value(closure, env_ptr, 3), 0)
+                ret(self.builder.insert_value(list_value, self.builder.sub(values[0], values[1]), 1))
+
+            # Going forwards (0..10).
+            with build_closure(module, closure_type, env_types) as (b, args, closure, c_func):
+                start = read_environment(b, args[0], env_types)[0]
+                b.ret(b.add(start, args[1]))
+
+            env_ptr = write_environment(self.builder, [values[0]])
+            list_value = tree.return_type(ir.Undefined)
+            list_value = self.builder.insert_value(list_value, self.builder.insert_value(closure, env_ptr, 3), 0)
+            ret(self.builder.insert_value(list_value, self.builder.sub(values[1], values[0]), 1))
 
-        env_ptr = write_environment(self.builder, [values[0]])
-        list_value = tree.return_type(ir.Undefined)
-        list_value = self.builder.insert_value(list_value, self.builder.insert_value(closure, env_ptr, 3), 0)
-        return self.builder.insert_value(list_value, self.builder.sub(values[1], values[0]), 1)
+        return phi
 
     def list_index(self, tree: TypeTree):
         list_value, i = self.visit_children(tree)
diff --git a/volpe/compile.py b/volpe/compile.py
index b872d7c..cd7f1c9 100644
--- a/volpe/compile.py
+++ b/volpe/compile.py
@@ -72,7 +72,7 @@ def __repr__(self):
         class CList(Structure):
             _fields_ = [("elems", POINTER(element_type)), ("length", c_int32)]
             def __repr__(self):
-                if depth == 0:
+                if depth < 2:
                     elems = getattr(self, "elems")
                     length = getattr(self, "length")
                     return "&<" + ", ".join([str(elem) for elem in elems[:length]]) + ">"
@@ -99,10 +99,10 @@ class CIterator(Structure):
             _fields_ = [("func", CFunc), ("length", c_int32)]
             def __repr__(self):
                 if depth == 0:
-                    # TODO maybe include length?
+                    # TODO Maybe include length.
                     func = volpe_type.elements[0].elements[0].pointee
                     return_type = get_type_name(func.return_type)
-                    return f"iterator of {return_type}"
+                    return f"iterator {return_type}"
                 return get_type_name(volpe_type)
         return CIterator
         
@@ -129,9 +129,9 @@ def get_type_name(volpe_type):
     if isinstance(volpe_type, VolpeList):
         return "*list*"
     if isinstance(volpe_type, VolpeClosure):
-        return "*function*"
+        return "*func*"
     if isinstance(volpe_type, VolpeIterator):
-        return "*iterator*"
+        return "*iter*"
         
     # Unknown type
     return None
diff --git a/volpe/run_volpe.py b/volpe/run_volpe.py
index 6c9f1fb..667aa65 100644
--- a/volpe/run_volpe.py
+++ b/volpe/run_volpe.py
@@ -62,11 +62,11 @@ def scope(name):
     with build_func(main_func) as (b, _):
         b: ir.IRBuilder
         res = b.call(func, [pint8(ir.Undefined)])
+        # TODO return vector as pointer if length is needed in print
         if isinstance(res.type, (VolpeTuple, VolpeList)):
             ptr = b.bitcast(b.call(module.malloc, [int32(res.type.get_abi_size(target_data))]), return_type)
             b.store(res, ptr)
             res = ptr
-        # TODO return list and vector as pointer
         b.ret(res)
 
     if verbose: