From: Ladislav Zejda <lzejda@gmail.com>
Date: Sat, 14 Mar 2015 10:12:11 +0000 (+0100)
Subject: Improve normalization with nested functions.
X-Git-Tag: ginac_1-6-4~8
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=0b985d5336debdd396f0fbeca8df850af5f569f4;ds=sidebyside

Improve normalization with nested functions.

normal() fails to fully normalize expressions where nested functions occur
multiple times because replace_with_symbol() searches repl for an
original expression but inserts into repl the substitued expression. Then
the repeated search does not work and a new symbol is introduced.

This patch fixes that by searching for the expression with the repl
substituted instead of for the original expression.
---

diff --git a/check/exam_normalization.cpp b/check/exam_normalization.cpp
index a184ad28..d98dec68 100644
--- a/check/exam_normalization.cpp
+++ b/check/exam_normalization.cpp
@@ -163,7 +163,12 @@ static unsigned exam_normal4()
 	e = (pow(x-y*2,4)/pow(pow(x,2)-pow(y,2)*4,2)+1)*(x+y*2)*(y+z)/(pow(x,2)+pow(y,2)*4);
 	d = (y*2 + z*2) / (x + y*2);
 	result += check_normal(e, d);
-	
+
+	// Replacement of nested functions with temporary symbols
+	e = x/(sqrt(sin(z)-1)) + y/(sqrt(sin(z)-1));
+	d = (x + y)/(sqrt(sin(z)-1));
+	result += check_normal(e, d);
+
 	return result;
 }
 
diff --git a/ginac/normal.cpp b/ginac/normal.cpp
index 97bd156a..f22bf27b 100644
--- a/ginac/normal.cpp
+++ b/ginac/normal.cpp
@@ -2006,16 +2006,18 @@ ex sqrfree_parfrac(const ex & a, const symbol & x)
  *  @see ex::normal */
 static ex replace_with_symbol(const ex & e, exmap & repl, exmap & rev_lookup)
 {
+	// Since the repl contains replaced expressions we should search for them
+	ex e_replaced = e.subs(repl, subs_options::no_pattern);
+
 	// Expression already replaced? Then return the assigned symbol
-	exmap::const_iterator it = rev_lookup.find(e);
+	exmap::const_iterator it = rev_lookup.find(e_replaced);
 	if (it != rev_lookup.end())
 		return it->second;
-	
+
 	// Otherwise create new symbol and add to list, taking care that the
 	// replacement expression doesn't itself contain symbols from repl,
 	// because subs() is not recursive
 	ex es = (new symbol)->setflag(status_flags::dynallocated);
-	ex e_replaced = e.subs(repl, subs_options::no_pattern);
 	repl.insert(std::make_pair(es, e_replaced));
 	rev_lookup.insert(std::make_pair(e_replaced, es));
 	return es;
@@ -2028,16 +2030,18 @@ static ex replace_with_symbol(const ex & e, exmap & repl, exmap & rev_lookup)
  *  @see basic::to_polynomial */
 static ex replace_with_symbol(const ex & e, exmap & repl)
 {
+	// Since the repl contains replaced expressions we should search for them
+	ex e_replaced = e.subs(repl, subs_options::no_pattern);
+
 	// Expression already replaced? Then return the assigned symbol
 	for (exmap::const_iterator it = repl.begin(); it != repl.end(); ++it)
-		if (it->second.is_equal(e))
+		if (it->second.is_equal(e_replaced))
 			return it->first;
-	
+
 	// Otherwise create new symbol and add to list, taking care that the
 	// replacement expression doesn't itself contain symbols from repl,
 	// because subs() is not recursive
 	ex es = (new symbol)->setflag(status_flags::dynallocated);
-	ex e_replaced = e.subs(repl, subs_options::no_pattern);
 	repl.insert(std::make_pair(es, e_replaced));
 	return es;
 }