From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Fri, 4 May 2001 23:55:36 +0000 (+0000)
Subject: - symbols can have a LaTeX name, e.g. symbol s("s", "\\sigma");
X-Git-Tag: release_0-8-3~24
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=f7a07ae7330a3543bb00aa7b659e2624d6c440c7

- symbols can have a LaTeX name, e.g. symbol s("s", "\\sigma");
- LaTeX output of indexed objects and tensors is much nicer
- simplify_indexed() can do arbitrary contractions in Dirac gamma strings
- constructing expressions like
    (x * dirac_ONE() + dirac_ONE()) * dirac_gamma(mu)
  resulted in an exception because mul::simplify_ncmul() wasn't implemented
  (maybe afrink didn't anticipate that an implementation would really be
  needed...)
---

diff --git a/ginac/clifford.cpp b/ginac/clifford.cpp
index 8a8bfe09..5a69cfd5 100644
--- a/ginac/clifford.cpp
+++ b/ginac/clifford.cpp
@@ -139,9 +139,9 @@ DEFAULT_COMPARE(diracone)
 DEFAULT_COMPARE(diracgamma)
 DEFAULT_COMPARE(diracgamma5)
 
-DEFAULT_PRINT(diracone, "ONE")
-DEFAULT_PRINT(diracgamma, "gamma")
-DEFAULT_PRINT(diracgamma5, "gamma5")
+DEFAULT_PRINT_LATEX(diracone, "ONE", "\\mathbb{1}")
+DEFAULT_PRINT_LATEX(diracgamma, "gamma", "\\gamma")
+DEFAULT_PRINT_LATEX(diracgamma5, "gamma5", "{\\gamma^5}")
 
 /** Contraction of a gamma matrix with something else. */
 bool diracgamma::contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const
@@ -151,34 +151,35 @@ bool diracgamma::contract_with(exvector::iterator self, exvector::iterator other
 	GINAC_ASSERT(is_ex_of_type(self->op(0), diracgamma));
 	unsigned char rl = ex_to_clifford(*self).get_representation_label();
 
-	if (is_ex_of_type(other->op(0), diracgamma)) {
+	if (is_ex_of_type(*other, clifford)) {
 
 		ex dim = ex_to_idx(self->op(1)).get_dim();
 
-		// gamma~mu*gamma.mu = dim*ONE
+		// gamma~mu gamma.mu = dim ONE
 		if (other - self == 1) {
 			*self = dim;
 			*other = dirac_ONE(rl);
 			return true;
 
-		// gamma~mu*gamma~alpha*gamma.mu = (2-dim)*gamma~alpha
+		// gamma~mu gamma~alpha gamma.mu = (2-dim) gamma~alpha
 		} else if (other - self == 2
 		        && is_ex_of_type(self[1], clifford)) {
 			*self = 2 - dim;
 			*other = _ex1();
 			return true;
 
-		// gamma~mu*gamma~alpha*gamma~beta*gamma.mu = 4*g~alpha~beta+(dim-4)*gamam~alpha*gamma~beta
+		// gamma~mu gamma~alpha gamma~beta gamma.mu = 4 g~alpha~beta + (dim-4) gamam~alpha gamma~beta
 		} else if (other - self == 3
 		        && is_ex_of_type(self[1], clifford)
 		        && is_ex_of_type(self[2], clifford)) {
-			*self = 4 * metric_tensor(self[1].op(1), self[2].op(1)) * dirac_ONE(rl) + (dim - 4) * self[1] * self[2];
+			*self = 4 * lorentz_g(self[1].op(1), self[2].op(1)) * dirac_ONE(rl) + (dim - 4) * self[1] * self[2];
 			self[1] = _ex1();
 			self[2] = _ex1();
 			*other = _ex1();
 			return true;
 
-		// gamma~mu*gamma~alpha*gamma~beta*gamma~delta*gamma.mu = -2*gamma~delta*gamma~beta*gamma~alpha+(4-dim)*gamma~alpha*gamma~beta*gamma~delta
+#if 0
+		// gamma~mu gamma~alpha gamma~beta gamma~delta gamma.mu = -2 gamma~delta gamma~beta gamma~alpha + (4-dim) gamma~alpha gamma~beta gamma~delta
 		} else if (other - self == 4
 		        && is_ex_of_type(self[1], clifford)
 		        && is_ex_of_type(self[2], clifford)
@@ -189,6 +190,30 @@ bool diracgamma::contract_with(exvector::iterator self, exvector::iterator other
 			self[3] = _ex1();
 			*other = _ex1();
 			return true;
+#endif
+
+		// gamma~mu S gamma~alpha gamma.mu = 2 gamma~alpha S - gamma~mu S gamma.mu gamma~alpha
+		// (commutate contracted indices towards each other, simplify_indexed()
+		// will re-expand and re-run the simplification)
+		} else {
+			exvector::iterator it = self + 1, next_to_last = other - 1;
+			while (it != other) {
+				if (!is_ex_of_type(*it, clifford))
+					return false;
+				it++;
+			}
+
+			it = self + 1;
+			ex S = _ex1();
+			while (it != next_to_last) {
+				S *= *it;
+				*it++ = _ex1();
+			}
+
+			*self = 2 * (*next_to_last) * S - (*self) * S * (*other) * (*next_to_last);
+			*next_to_last = _ex1();
+			*other = _ex1();
+			return true;
 		}
 	}
 
@@ -364,12 +389,12 @@ ex dirac_trace(const ex & e, unsigned char rl)
 		if (has_gamma5) {
 
 			// Trace of gamma5 * odd number of gammas and trace of
-			// gamma5 * gamma_mu * gamma_nu are zero
+			// gamma5 * gamma.mu * gamma.nu are zero
 			if ((num & 1) == 0 || num == 3)
 				return _ex0();
 
 			// Tr gamma5 S_2k =
-			//   epsilon0123_mu1_mu2_mu3_mu4 * Tr gamma_mu1 gamma_mu2 gamma_mu3 gamma_mu4 S_2k
+			//   epsilon0123.mu1.mu2.mu3.mu4 * Tr gamma.mu1 gamma.mu2 gamma.mu3 gamma.mu4 S_2k
 			ex dim = ex_to_idx(e.op(1).op(1)).get_dim();
 			varidx mu1((new symbol)->setflag(status_flags::dynallocated), dim),
 			       mu2((new symbol)->setflag(status_flags::dynallocated), dim),
@@ -393,17 +418,17 @@ ex dirac_trace(const ex & e, unsigned char rl)
 			if ((num & 1) == 1)
 				return _ex0();
 
-			// Tr gamma_mu gamma_nu = 4 g_mu_nu
+			// Tr gamma.mu gamma.nu = 4 g.mu.nu
 			if (num == 2)
 				return 4 * lorentz_g(e.op(0).op(1), e.op(1).op(1));
 
 			// Traces of 4 or more gammas are computed recursively:
-			// Tr gamma_mu1 gamma_mu2 ... gamma_mun =
-			//   + eta_mu1_mu2 * Tr gamma_mu3 ... gamma_mun
-			//   - eta_mu1_mu3 * Tr gamma_mu2 gamma_mu4 ... gamma_mun
-			//   + eta_mu1_mu4 * Tr gamma_mu3 gamma_mu3 gamma_mu5 ... gamma_mun
+			// Tr gamma.mu1 gamma.mu2 ... gamma.mun =
+			//   + g.mu1.mu2 * Tr gamma.mu3 ... gamma.mun
+			//   - g.mu1.mu3 * Tr gamma.mu2 gamma.mu4 ... gamma.mun
+			//   + g.mu1.mu4 * Tr gamma.mu3 gamma.mu3 gamma.mu5 ... gamma.mun
 			//   - ...
-			//   + eta_mu1_mun * Tr gamma_mu2 ... gamma_mu(n-1)
+			//   + g.mu1.mun * Tr gamma.mu2 ... gamma.mu(n-1)
 			exvector v(num - 2);
 			int sign = 1;
 			const ex &ix1 = e.op(0).op(1);
diff --git a/ginac/color.cpp b/ginac/color.cpp
index e36c1cbe..77cf89c4 100644
--- a/ginac/color.cpp
+++ b/ginac/color.cpp
@@ -145,7 +145,7 @@ DEFAULT_COMPARE(su3t)
 DEFAULT_COMPARE(su3f)
 DEFAULT_COMPARE(su3d)
 
-DEFAULT_PRINT(su3one, "ONE")
+DEFAULT_PRINT_LATEX(su3one, "ONE", "\\mathbb{1}")
 DEFAULT_PRINT(su3t, "T")
 DEFAULT_PRINT(su3f, "f")
 DEFAULT_PRINT(su3d, "d")
diff --git a/ginac/constant.cpp b/ginac/constant.cpp
index c056a96a..e86a2964 100644
--- a/ginac/constant.cpp
+++ b/ginac/constant.cpp
@@ -41,7 +41,7 @@ GINAC_IMPLEMENT_REGISTERED_CLASS(constant, basic)
 
 // public
 
-constant::constant() : basic(TINFO_constant), name(""), ef(0), number(0), serial(next_serial++)
+constant::constant() : basic(TINFO_constant), ef(0), number(0), serial(next_serial++)
 {
 	debugmsg("constant default ctor",LOGLEVEL_CONSTRUCT);
 }
@@ -53,6 +53,7 @@ void constant::copy(const constant & other)
 {
 	inherited::copy(other);
 	name = other.name;
+	TeX_name = other.TeX_name;
 	serial = other.serial;
 	ef = other.ef;
 	if (other.number != 0)
@@ -74,17 +75,25 @@ void constant::destroy(bool call_parent)
 
 // public
 
-constant::constant(const std::string & initname, evalffunctype efun)
+constant::constant(const std::string & initname, evalffunctype efun, const std::string & texname)
   : basic(TINFO_constant), name(initname), ef(efun), number(0), serial(next_serial++)
 {
 	debugmsg("constant ctor from string, function",LOGLEVEL_CONSTRUCT);
+	if (texname.empty())
+		TeX_name = "\\mbox{" + name + "}";
+	else
+		TeX_name = texname;
 	setflag(status_flags::evaluated);
 }
 
-constant::constant(const std::string & initname, const numeric & initnumber)
+constant::constant(const std::string & initname, const numeric & initnumber, const std::string & texname)
   : basic(TINFO_constant), name(initname), ef(0), number(new numeric(initnumber)), serial(next_serial++)
 {
 	debugmsg("constant ctor from string, numeric",LOGLEVEL_CONSTRUCT);
+	if (texname.empty())
+		TeX_name = "\\mbox{" + name + "}";
+	else
+		TeX_name = texname;
 	setflag(status_flags::evaluated);
 }
 
@@ -135,16 +144,9 @@ void constant::print(const print_context & c, unsigned level) const
 		c.s << std::string(level, ' ') << name << " (" << class_name() << ")"
 		    << std::hex << ", hash=0x" << hashvalue << ", flags=0x" << flags << std::dec
 		    << std::endl;
-	} else if (is_of_type(c, print_latex)) {
-		if (name=="Pi")
-			c.s << "\\pi";
-		else if (name=="Euler")
-			c.s << "\\gamma_E";
-		else if (name=="Catalan")
-			c.s << "G";
-		else
-			c.s << "\\mbox{"+name+"}";
-	} else
+	} else if (is_of_type(c, print_latex))
+		c.s << TeX_name;
+	else
 		c.s << name;
 }
 
@@ -237,13 +239,13 @@ unsigned constant::next_serial = 0;
 //////////
 
 /**  Pi. (3.14159...)  Diverts straight into CLN for evalf(). */
-const constant Pi("Pi", PiEvalf);
+const constant Pi("Pi", PiEvalf, "\\pi");
 
 /** Euler's constant. (0.57721...)  Sometimes called Euler-Mascheroni constant.
  *  Diverts straight into CLN for evalf(). */
-const constant Euler("Euler", EulerEvalf);
+const constant Euler("Euler", EulerEvalf, "\\gamma_E");
 
 /** Catalan's constant. (0.91597...)  Diverts straight into CLN for evalf(). */
-const constant Catalan("Catalan", CatalanEvalf);
+const constant Catalan("Catalan", CatalanEvalf, "G");
 
 } // namespace GiNaC
diff --git a/ginac/constant.h b/ginac/constant.h
index fdf06615..bf85b382 100644
--- a/ginac/constant.h
+++ b/ginac/constant.h
@@ -43,8 +43,8 @@ class constant : public basic
 	
 	// other ctors
 public:
-	constant(const std::string & initname, evalffunctype efun = 0);
-	constant(const std::string & initname, const numeric & initnumber);
+	constant(const std::string & initname, evalffunctype efun = 0, const std::string & texname = std::string());
+	constant(const std::string & initname, const numeric & initnumber, const std::string & texname = std::string());
 	
 	// functions overriding virtual functions from bases classes
 public:
@@ -67,10 +67,11 @@ protected:
 // member variables
 	
 private:
-	std::string name;   ///< printname of this constant
+	std::string name;     ///< printname of this constant
+	std::string TeX_name; ///< LaTeX name
 	evalffunctype ef;
-	numeric *number;    ///< numerical value this constant evalf()s to
-	unsigned serial;    ///< unique serial number for comparison
+	numeric *number;      ///< numerical value this constant evalf()s to
+	unsigned serial;      ///< unique serial number for comparison
 	static unsigned next_serial;
 };
 
diff --git a/ginac/idx.cpp b/ginac/idx.cpp
index 9f31a9ad..44427a6a 100644
--- a/ginac/idx.cpp
+++ b/ginac/idx.cpp
@@ -136,11 +136,12 @@ void idx::print(const print_context & c, unsigned level) const
 
 	} else {
 
-		c.s << ".";
+		if (!is_of_type(c, print_latex))
+			c.s << ".";
 		bool need_parens = !(is_ex_exactly_of_type(value, numeric) || is_ex_of_type(value, symbol));
 		if (need_parens)
 			c.s << "(";
-		c.s << value;
+		value.print(c);
 		if (need_parens)
 			c.s << ")";
 	}
@@ -162,14 +163,16 @@ void varidx::print(const print_context & c, unsigned level) const
 
 	} else {
 
-		if (covariant)
-			c.s << ".";
-		else
-			c.s << "~";
+		if (!is_of_type(c, print_latex)) {
+			if (covariant)
+				c.s << ".";
+			else
+				c.s << "~";
+		}
 		bool need_parens = !(is_ex_exactly_of_type(value, numeric) || is_ex_of_type(value, symbol));
 		if (need_parens)
 			c.s << "(";
-		c.s << value;
+		value.print(c);
 		if (need_parens)
 			c.s << ")";
 	}
diff --git a/ginac/indexed.cpp b/ginac/indexed.cpp
index 6fbe40b9..3c7005e2 100644
--- a/ginac/indexed.cpp
+++ b/ginac/indexed.cpp
@@ -199,14 +199,20 @@ void indexed::print(const print_context & c, unsigned level) const
 
 	} else {
 
+		bool is_tex = is_of_type(c, print_latex);
 		const ex & base = seq[0];
 		bool need_parens = is_ex_exactly_of_type(base, add) || is_ex_exactly_of_type(base, mul)
-		                || is_ex_exactly_of_type(base, ncmul) || is_ex_exactly_of_type(base, power);
+		                || is_ex_exactly_of_type(base, ncmul) || is_ex_exactly_of_type(base, power)
+		                || is_ex_of_type(base, indexed);
+		if (is_tex)
+			c.s << "{";
 		if (need_parens)
 			c.s << "(";
 		base.print(c);
 		if (need_parens)
 			c.s << ")";
+		if (is_tex)
+			c.s << "}";
 		printindices(c, level);
 	}
 }
@@ -409,10 +415,40 @@ ex indexed::expand(unsigned options) const
 void indexed::printindices(const print_context & c, unsigned level) const
 {
 	if (seq.size() > 1) {
+
 		exvector::const_iterator it=seq.begin() + 1, itend = seq.end();
-		while (it != itend) {
-			it->print(c, level);
-			it++;
+
+		if (is_of_type(c, print_latex)) {
+
+			// TeX output: group by variance
+			bool first = true;
+			bool covariant = true;
+
+			while (it != itend) {
+				bool cur_covariant = (is_ex_of_type(*it, varidx) ? ex_to_varidx(*it).is_covariant() : true);
+				if (first || cur_covariant != covariant) {
+					if (!first)
+						c.s << "}";
+					covariant = cur_covariant;
+					if (covariant)
+						c.s << "_{";
+					else
+						c.s << "^{";
+				}
+				it->print(c, level);
+				c.s << " ";
+				first = false;
+				it++;
+			}
+			c.s << "}";
+
+		} else {
+
+			// Ordinary output
+			while (it != itend) {
+				it->print(c, level);
+				it++;
+			}
 		}
 	}
 }
@@ -631,11 +667,12 @@ try_again:
 			if (contracted) {
 contraction_done:
 				if (is_ex_exactly_of_type(*it1, add) || is_ex_exactly_of_type(*it2, add)
-				 || is_ex_exactly_of_type(*it1, mul) || is_ex_exactly_of_type(*it2, mul)) {
+				 || is_ex_exactly_of_type(*it1, mul) || is_ex_exactly_of_type(*it2, mul)
+				 || is_ex_exactly_of_type(*it1, ncmul) || is_ex_exactly_of_type(*it2, ncmul)) {
 
 					// One of the factors became a sum or product:
 					// re-expand expression and run again
-					ex r = non_commutative ? ex(ncmul(v)) : ex(mul(v));
+					ex r = (non_commutative ? ex(ncmul(v)) : ex(mul(v)));
 					return simplify_indexed(r, free_indices, sp);
 				}
 
diff --git a/ginac/mul.cpp b/ginac/mul.cpp
index 27451f6b..75f74b4b 100644
--- a/ginac/mul.cpp
+++ b/ginac/mul.cpp
@@ -405,7 +405,16 @@ ex mul::evalf(int level) const
 
 ex mul::simplify_ncmul(const exvector & v) const
 {
-	throw(std::logic_error("mul::simplify_ncmul() should never have been called!"));
+	if (seq.size()==0) {
+		return inherited::simplify_ncmul(v);
+	}
+
+	// Find first noncommutative element and call its simplify_ncmul()
+	for (epvector::const_iterator cit=seq.begin(); cit!=seq.end(); ++cit) {
+		if (cit->rest.return_type() == return_types::noncommutative)
+			return cit->rest.simplify_ncmul(v);
+	}
+	return inherited::simplify_ncmul(v);
 }
 
 // protected
diff --git a/ginac/symbol.cpp b/ginac/symbol.cpp
index bebb8776..29d46bbf 100644
--- a/ginac/symbol.cpp
+++ b/ginac/symbol.cpp
@@ -41,7 +41,7 @@ GINAC_IMPLEMENT_REGISTERED_CLASS_NO_CTORS(symbol, basic)
 symbol::symbol() : inherited(TINFO_symbol), serial(next_serial++)
 {
 	debugmsg("symbol default ctor", LOGLEVEL_CONSTRUCT);
-	name = autoname_prefix()+ToString(serial);
+	name = TeX_name = autoname_prefix()+ToString(serial);
 	asexinfop = new assigned_ex_info;
 	setflag(status_flags::evaluated | status_flags::expanded);
 }
@@ -51,6 +51,7 @@ void symbol::copy(const symbol & other)
 {
 	inherited::copy(other);
 	name = other.name;
+	TeX_name = other.TeX_name;
 	serial = other.serial;
 	asexinfop = other.asexinfop;
 	++asexinfop->refcount;
@@ -80,6 +81,17 @@ symbol::symbol(const std::string & initname) : inherited(TINFO_symbol)
 {
 	debugmsg("symbol ctor from string", LOGLEVEL_CONSTRUCT);
 	name = initname;
+	TeX_name = default_TeX_name();
+	serial = next_serial++;
+	asexinfop = new assigned_ex_info;
+	setflag(status_flags::evaluated | status_flags::expanded);
+}
+
+symbol::symbol(const std::string & initname, const std::string & texname) : inherited(TINFO_symbol)
+{
+	debugmsg("symbol ctor from string", LOGLEVEL_CONSTRUCT);
+	name = initname;
+	TeX_name = texname;
 	serial = next_serial++;
 	asexinfop = new assigned_ex_info;
 	setflag(status_flags::evaluated | status_flags::expanded);
@@ -96,6 +108,8 @@ symbol::symbol(const archive_node &n, const lst &sym_lst) : inherited(n, sym_lst
 	serial = next_serial++;
 	if (!(n.find_string("name", name)))
 		name = autoname_prefix() + ToString(serial);
+	if (!(n.find_string("TeXname", TeX_name)))
+		TeX_name = default_TeX_name();
 	asexinfop = new assigned_ex_info;
 	setflag(status_flags::evaluated);
 }
@@ -118,6 +132,8 @@ void symbol::archive(archive_node &n) const
 {
 	inherited::archive(n);
 	n.add_string("name", name);
+	if (TeX_name != default_TeX_name())
+		n.add_string("TeX_name", TeX_name);
 }
 
 //////////
@@ -143,25 +159,9 @@ void symbol::print(const print_context & c, unsigned level) const
 		    << std::hex << ", hash=0x" << hashvalue << ", flags=0x" << flags << std::dec
 		    << std::endl;
 
-	} else if (is_of_type(c, print_latex)) {
-		if (name=="alpha"        || name=="beta"         || name=="gamma"
-		 || name=="delta"        || name=="epsilon"      || name=="varepsilon"
-		 || name=="zeta"         || name=="eta"          || name=="theta"
-		 || name=="vartheta"     || name=="iota"         || name=="kappa"
-		 || name=="lambda"       || name=="mu"           || name=="nu"
-		 || name=="xi"           || name=="omicron"      || name=="pi"
-		 || name=="varpi"        || name=="rho"          || name=="varrho"
-		 || name=="sigma"        || name=="varsigma"     || name=="tau"
-		 || name=="upsilon"      || name=="phi"          || name=="varphix"
-		 || name=="chi"          || name=="psi"          || name=="omega"
-		 || name=="Gamma"        || name=="Delta"        || name=="Theta"
-		 || name=="Lambda"       || name=="Xi"           || name=="Pi"
-		 || name=="Sigma"        || name=="Upsilon"      || name=="Phi"
-		 || name=="Psi"          || name=="Omega")
-			c.s << "\\" << name;
-		else
-			c.s << name;
-	} else
+	} else if (is_of_type(c, print_latex))
+		c.s << TeX_name;
+	else
 		c.s << name;
 }
 
@@ -313,6 +313,28 @@ std::string & symbol::autoname_prefix(void)
 	return *s;
 }
 
+/** Return default TeX name for symbol. This recognizes some greek letters. */
+std::string symbol::default_TeX_name(void) const
+{
+	if (name=="alpha"        || name=="beta"         || name=="gamma"
+	 || name=="delta"        || name=="epsilon"      || name=="varepsilon"
+	 || name=="zeta"         || name=="eta"          || name=="theta"
+	 || name=="vartheta"     || name=="iota"         || name=="kappa"
+	 || name=="lambda"       || name=="mu"           || name=="nu"
+	 || name=="xi"           || name=="omicron"      || name=="pi"
+	 || name=="varpi"        || name=="rho"          || name=="varrho"
+	 || name=="sigma"        || name=="varsigma"     || name=="tau"
+	 || name=="upsilon"      || name=="phi"          || name=="varphix"
+	 || name=="chi"          || name=="psi"          || name=="omega"
+	 || name=="Gamma"        || name=="Delta"        || name=="Theta"
+	 || name=="Lambda"       || name=="Xi"           || name=="Pi"
+	 || name=="Sigma"        || name=="Upsilon"      || name=="Phi"
+	 || name=="Psi"          || name=="Omega")
+		return "\\" + name;
+	else
+		return name;
+}
+
 //////////
 // static member variables
 //////////
diff --git a/ginac/symbol.h b/ginac/symbol.h
index 1f494cf2..aec27aee 100644
--- a/ginac/symbol.h
+++ b/ginac/symbol.h
@@ -68,6 +68,7 @@ protected:
 	// other ctors
 public:
 	explicit symbol(const std::string & initname);
+	explicit symbol(const std::string & initname, const std::string & texname);
 	
 	// functions overriding virtual functions from base classes
 public:
@@ -99,13 +100,15 @@ public:
 	std::string get_name(void) const { return name; }
 private:
 	std::string & autoname_prefix(void);
+	std::string default_TeX_name(void) const;
 
 // member variables
 
 protected:
 	assigned_ex_info * asexinfop;   ///< ptr to assigned expression, deprecated
-	unsigned serial;    ///< unique serial number for comparison
-	std::string name;   ///< printname of this symbol
+	unsigned serial;       ///< unique serial number for comparison
+	std::string name;      ///< printname of this symbol
+	std::string TeX_name;  ///< LaTeX name of this symbol
 private:
 	static unsigned next_serial;
 };
diff --git a/ginac/tensor.cpp b/ginac/tensor.cpp
index d16bbfce..928c6568 100644
--- a/ginac/tensor.cpp
+++ b/ginac/tensor.cpp
@@ -162,10 +162,10 @@ int tensepsilon::compare_same_type(const basic & other) const
 		return inherited::compare_same_type(other);
 }
 
-DEFAULT_PRINT(tensdelta, "delta")
+DEFAULT_PRINT_LATEX(tensdelta, "delta", "\\delta")
 DEFAULT_PRINT(tensmetric, "g")
-DEFAULT_PRINT(minkmetric, "eta")
-DEFAULT_PRINT(tensepsilon, "eps")
+DEFAULT_PRINT_LATEX(minkmetric, "eta", "\\eta")
+DEFAULT_PRINT_LATEX(tensepsilon, "eps", "\\epsilon")
 
 /** Automatic symbolic evaluation of an indexed delta tensor. */
 ex tensdelta::eval_indexed(const basic & i) const
diff --git a/ginac/utils.h b/ginac/utils.h
index c2a5f232..79719feb 100644
--- a/ginac/utils.h
+++ b/ginac/utils.h
@@ -301,6 +301,18 @@ void classname::print(const print_context & c, unsigned level) const \
 		c.s << text; \
 }
 
+#define DEFAULT_PRINT_LATEX(classname, text, latex) \
+void classname::print(const print_context & c, unsigned level) const \
+{ \
+	debugmsg(#classname " print", LOGLEVEL_PRINT); \
+	if (is_of_type(c, print_tree)) \
+		inherited::print(c, level); \
+	else if (is_of_type(c, print_latex)) \
+		c.s << latex; \
+	else \
+		c.s << text; \
+}
+
 } // namespace GiNaC
 
 #endif // ndef __GINAC_UTILS_H__