From jrheinlaender at gmx.de  Sun Feb  9 15:51:06 2025
From: jrheinlaender at gmx.de (=?UTF-8?Q?Jan_Rheinl=C3=A4nder?=)
Date: Sun, 9 Feb 2025 15:51:06 +0100
Subject: [GiNaC-devel] Patch for base of natural logarithm
Message-ID: <a9623a3d-dfef-41e4-84d1-fa215d0374ca@gmx.de>

Hi,

this is a patch to add the base of the natural logarithm as a new 
constant EulerNum, and ensure that log(EulerNum) evaluates to 1.

Of course, exp(1) will do fine for calculations. But for printing, it is 
nicer to see e^x instead of exp(1)^x or 2.718^x.

Hope this is useful.

Jan

---
 ?ginac/constant.cpp????? | 5 +++++
 ?ginac/constant.h??????? | 1 +
 ?ginac/inifcns_trans.cpp | 3 +++
 ?ginac/numeric.cpp?????? | 5 +++++
 ?ginac/numeric.h???????? | 1 +
 ?ginsh/ginsh_lexer.lpp?? | 1 +
 ?6 files changed, 16 insertions(+)

diff --git a/ginac/constant.cpp b/ginac/constant.cpp
index a89711ef..60af44bc 100644
--- a/ginac/constant.cpp
+++ b/ginac/constant.cpp
@@ -91,6 +91,8 @@ void constant::read_archive(const archive_node &n, lst 
&sym_lst)
 ???????????? *this = Catalan;
 ???????? else if (s == Euler.name)
 ???????????? *this = Euler;
+??????? else if (s == EulerNum.name)
+??????????? *this = EulerNum;
 ???????? else
 ???????????? throw (std::runtime_error("unknown constant '" + s + "' in 
archive"));
 ???? } else
@@ -254,4 +256,7 @@ const constant Euler("Euler", EulerEvalf, 
"\\gamma_E", domain::positive);
 ?/** Catalan's constant. (0.91597...)? Diverts straight into CLN for 
evalf(). */
 ?const constant Catalan("Catalan", CatalanEvalf, "G", domain::positive);

+/** Base of the natural logarithm */
+const constant EulerNum("EulerNum", EulerNumEvalf, "\\mathit{e}", 
domain::positive);
+
 ?} // namespace GiNaC
diff --git a/ginac/constant.h b/ginac/constant.h
index 92d07941..24839d46 100644
--- a/ginac/constant.h
+++ b/ginac/constant.h
@@ -82,6 +82,7 @@ GINAC_DECLARE_UNARCHIVER(constant);
 ?extern const constant Pi;
 ?extern const constant Catalan;
 ?extern const constant Euler;
+extern const constant EulerNum;

 ?} // namespace GiNaC

diff --git a/ginac/inifcns_trans.cpp b/ginac/inifcns_trans.cpp
index 6f577bae..ef5f52f1 100644
--- a/ginac/inifcns_trans.cpp
+++ b/ginac/inifcns_trans.cpp
@@ -202,6 +202,9 @@ static ex log_eval(const ex & x)
 ???????????? return log(ex_to<numeric>(x));
 ???? }

+??? if (x.is_equal(EulerNum))
+??????????? return *_num1_p;
+
 ???? // log(exp(t)) -> t (if -Pi < t.imag() <= Pi):
 ???? if (is_ex_the_function(x, exp)) {
 ???????? const ex &t = x.op(0);
diff --git a/ginac/numeric.cpp b/ginac/numeric.cpp
index 6da79977..addc012d 100644
--- a/ginac/numeric.cpp
+++ b/ginac/numeric.cpp
@@ -2515,6 +2515,11 @@ ex CatalanEvalf()
 ???? return numeric(cln::catalanconst(cln::default_float_format));
 ?}

+/** Floating point evaluation of base of natural logarithm. */
+ex EulerNumEvalf()
+{
+??? return exp(*_num1_p); // Suggestion by Vladimir Kisil on ginac-devel
+}

 ?/** _numeric_digits default ctor, checking for singleton invariance. */
 ?_numeric_digits::_numeric_digits()
diff --git a/ginac/numeric.h b/ginac/numeric.h
index 0673d9a5..d25670f9 100644
--- a/ginac/numeric.h
+++ b/ginac/numeric.h
@@ -325,6 +325,7 @@ inline const numeric denom(const numeric &x)
 ?ex PiEvalf();
 ?ex EulerEvalf();
 ?ex CatalanEvalf();
+ex EulerNumEvalf();


 ?} // namespace GiNaC
diff --git a/ginsh/ginsh_lexer.lpp b/ginsh/ginsh_lexer.lpp
index 6e0732e7..bcfecd10 100644
--- a/ginsh/ginsh_lexer.lpp
+++ b/ginsh/ginsh_lexer.lpp
@@ -75,6 +75,7 @@ AN??? [0-9a-zA-Z_]
 ?Pi??????????? yylval = Pi; return T_LITERAL;
 ?Euler??????????? yylval = Euler; return T_LITERAL;
 ?Catalan??????????? yylval = Catalan; return T_LITERAL;
+EulerNum??????? yylval = EulerNum; return T_LITERAL;
 ?FAIL??????????? yylval = *new fail(); return T_LITERAL;
 ?I??????????? yylval = I; return T_NUMBER;
 ?Digits??????????? yylval = (long)Digits; return T_DIGITS;
-- 
2.43.0


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