From dddcf2b00b00dc24ad28acdd64f0d778d3c666d6 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Tue, 31 May 2016 09:55:00 +0100
Subject: [PATCH] Don't use lanczos approximations for variable precision
 types. When the precision is '0'.

---
 include/boost/multiprecision/detail/big_lanczos.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/boost/multiprecision/detail/big_lanczos.hpp b/include/boost/multiprecision/detail/big_lanczos.hpp
index 03d3203e..0a5a154d 100644
--- a/include/boost/multiprecision/detail/big_lanczos.hpp
+++ b/include/boost/multiprecision/detail/big_lanczos.hpp
@@ -21,10 +21,10 @@ struct lanczos<multiprecision::number<Backend, ExpressionTemplates>, Policy>
 {
    typedef typename boost::math::policies::precision<multiprecision::number<Backend, ExpressionTemplates>, Policy>::type precision_type;
    typedef typename mpl::if_c<
-      precision_type::value <= 73,
+      precision_type::value && (precision_type::value <= 73),
       lanczos13UDT,
       typename mpl::if_c<
-         precision_type::value <= 122,
+      precision_type::value&& (precision_type::value <= 122),
          lanczos22UDT,
          undefined_lanczos
       >::type