X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?a=blobdiff_plain;f=ginac%2Finifcns.cpp;h=ec74a435de0774290f6d95baa221690b87420de7;hb=fa1ffcfdc9da97a6fb7cc2c9c36fe1fc45c808a9;hp=4e426f4ca3d097abe0ab7cb84381d0f5d4442d6a;hpb=63f3e977f92d51ea173382a9b7c4c3b18bda7b8e;p=ginac.git

diff --git a/ginac/inifcns.cpp b/ginac/inifcns.cpp
index 4e426f4c..ec74a435 100644
--- a/ginac/inifcns.cpp
+++ b/ginac/inifcns.cpp
@@ -3,7 +3,7 @@
  *  Implementation of GiNaC's initially known functions. */
 
 /*
- *  GiNaC Copyright (C) 1999-2018 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2020 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -321,6 +321,8 @@ static ex abs_expand(const ex & arg, unsigned options)
 static ex abs_expl_derivative(const ex & arg, const symbol & s)
 {
 	ex diff_arg = arg.diff(s);
+	if (arg.info(info_flags::real))
+		return diff_arg*(2*step(arg) - 1);
 	return (diff_arg*arg.conjugate()+arg*diff_arg.conjugate())/2/abs(arg);
 }
 
@@ -1038,6 +1040,29 @@ REGISTER_FUNCTION(Order, eval_func(Order_eval).
 // Solve linear system
 //////////
 
+class symbolset {
+	exset s;
+	void insert_symbols(const ex &e)
+	{
+		if (is_a<symbol>(e)) {
+			s.insert(e);
+		} else {
+			for (const ex &sube : e) {
+				insert_symbols(sube);
+			}
+		}
+	}
+public:
+	explicit symbolset(const ex &e)
+	{
+		insert_symbols(e);
+	}
+	bool has(const ex &e) const
+	{
+		return s.find(e) != s.end();
+	}
+};
+
 ex lsolve(const ex &eqns, const ex &symbols, unsigned options)
 {
 	// solve a system of linear equations
@@ -1053,20 +1078,20 @@ ex lsolve(const ex &eqns, const ex &symbols, unsigned options)
 	}
 	
 	// syntax checks
-	if (!eqns.info(info_flags::list)) {
-		throw(std::invalid_argument("lsolve(): 1st argument must be a list or an equation"));
+	if (!(eqns.info(info_flags::list) || eqns.info(info_flags::exprseq))) {
+		throw(std::invalid_argument("lsolve(): 1st argument must be a list, a sequence, or an equation"));
 	}
 	for (size_t i=0; i<eqns.nops(); i++) {
 		if (!eqns.op(i).info(info_flags::relation_equal)) {
 			throw(std::invalid_argument("lsolve(): 1st argument must be a list of equations"));
 		}
 	}
-	if (!symbols.info(info_flags::list)) {
-		throw(std::invalid_argument("lsolve(): 2nd argument must be a list or a symbol"));
+	if (!(symbols.info(info_flags::list) || symbols.info(info_flags::exprseq))) {
+		throw(std::invalid_argument("lsolve(): 2nd argument must be a list, a sequence, or a symbol"));
 	}
 	for (size_t i=0; i<symbols.nops(); i++) {
 		if (!symbols.op(i).info(info_flags::symbol)) {
-			throw(std::invalid_argument("lsolve(): 2nd argument must be a list of symbols"));
+			throw(std::invalid_argument("lsolve(): 2nd argument must be a list or a sequence of symbols"));
 		}
 	}
 	
@@ -1077,8 +1102,11 @@ ex lsolve(const ex &eqns, const ex &symbols, unsigned options)
 	
 	for (size_t r=0; r<eqns.nops(); r++) {
 		const ex eq = eqns.op(r).op(0)-eqns.op(r).op(1); // lhs-rhs==0
+		const symbolset syms(eq);
 		ex linpart = eq;
 		for (size_t c=0; c<symbols.nops(); c++) {
+			if (!syms.has(symbols.op(c)))
+				continue;
 			const ex co = eq.coeff(ex_to<symbol>(symbols.op(c)),1);
 			linpart -= co*symbols.op(c);
 			sys(r,c) = co;
@@ -1088,11 +1116,13 @@ ex lsolve(const ex &eqns, const ex &symbols, unsigned options)
 	}
 	
 	// test if system is linear and fill vars matrix
+	const symbolset sys_syms(sys);
+	const symbolset rhs_syms(rhs);
 	for (size_t i=0; i<symbols.nops(); i++) {
 		vars(i,0) = symbols.op(i);
-		if (sys.has(symbols.op(i)))
+		if (sys_syms.has(symbols.op(i)))
 			throw(std::logic_error("lsolve: system is not linear"));
-		if (rhs.has(symbols.op(i)))
+		if (rhs_syms.has(symbols.op(i)))
 			throw(std::logic_error("lsolve: system is not linear"));
 	}