From: Alexei Sheplyakov <Alexei.Sheplyakov@gmail.com>
Date: Sat, 3 Aug 2013 14:01:42 +0000 (+0300)
Subject: Introduce status_flags::{is_positive,is_negative,purely_indefinite}
X-Git-Tag: release_1-6-3~43
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=50ed15a65e858858999be45301b3f49821cb1e71

Introduce status_flags::{is_positive,is_negative,purely_indefinite}

Quite a number of transformations can be applied if the expression
is known to be positive (negative) (for instance, sqrt(x^2*y^2) = x*y
if x >= 0 and y >= 0). However the check itself might be quite expensive.
Hence a few status_flags are introduced to cache the result.
---

diff --git a/ginac/flags.h b/ginac/flags.h
index 8f8f25df..e38d9c58 100644
--- a/ginac/flags.h
+++ b/ginac/flags.h
@@ -196,7 +196,10 @@ public:
 		hash_calculated = 0x0008, ///< .calchash() has already done its job
 		not_shareable   = 0x0010, ///< don't share instances of this object between different expressions unless explicitly asked to (used by ex::compare())
 		has_indices	= 0x0020,
-		has_no_indices	= 0x0040  // ! (has_indices || has_no_indices) means "don't know"
+		has_no_indices	= 0x0040, // ! (has_indices || has_no_indices) means "don't know"
+		is_positive	= 0x0080,
+		is_negative	= 0x0100,
+		purely_indefinite = 0x0200  // If set in a mul, then it does not contains any terms with determined signs, used in power::expand()
 	};
 };
 
@@ -256,7 +259,10 @@ public:
 		idx,
 
 		// answered by classes numeric, symbol, add, mul, power
-		expanded
+		expanded,
+
+		// is meaningful for mul only
+		indefinite
 	};
 };