From a33dc8540f4efc63ad7d39e7a544b10778815573 Mon Sep 17 00:00:00 2001
From: Sei Lisa <sei-lisa@email.fake>
Date: Sat, 2 Jun 2018 16:47:07 +0200
Subject: [PATCH] Implement ~-~-~-expr -> expr + -3

Gets rid of a TODO
---
 lslopt/lslfoldconst.py | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lslopt/lslfoldconst.py b/lslopt/lslfoldconst.py
index a4046ef..6b755ef 100644
--- a/lslopt/lslfoldconst.py
+++ b/lslopt/lslfoldconst.py
@@ -688,7 +688,20 @@ class foldconst(object):
             subexpr = child[0]
             node.SEF = subexpr.SEF
 
-            # TODO: ~-~-~-expr  ->  expr + -3  (see NEG for similar exp + 3)
+            if child[0].nt == 'NEG':
+                track = child[0].ch[0]
+                const = -1
+                while track.nt == '~' and track.ch[0].nt == 'NEG':
+                    const -= 1
+                    track = track.ch[0].ch[0]
+                if const < -2:
+                    # ~-~-~-expr  ->  expr + (-3)
+                    node = nr(nt='CONST', t='integer', SEF=True, value=const)
+                    node = nr(nt='+', t='integer', ch=[node, track],
+                        SEF=track.SEF)
+                    parent[index] = node
+                    self.FoldTree(parent, index)
+                    return
 
             if subexpr.nt == '~':
                 # Double negation: ~~expr