From: Jens Vollinga <vollinga@thep.physik.uni-mainz.de>
Date: Thu, 10 Nov 2005 17:36:28 +0000 (+0000)
Subject: Added callback mechanism to watch changes to 'Digits' (to be used for look-up tables)
X-Git-Tag: release_1-4-0~133
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=6715b097ae926fecfc62e53d4af38b7217634908

Added callback mechanism to watch changes to 'Digits' (to be used for look-up tables)
---

diff --git a/ginac/numeric.cpp b/ginac/numeric.cpp
index 9670c6b3..f62b0d25 100644
--- a/ginac/numeric.cpp
+++ b/ginac/numeric.cpp
@@ -1999,14 +1999,25 @@ _numeric_digits::_numeric_digits()
 		throw(std::runtime_error("I told you not to do instantiate me!"));
 	too_late = true;
 	cln::default_float_format = cln::float_format(17);
+
+	// add callbacks for built-in functions
+	// like ... add_callback(Li_lookuptable);
 }
 
 
 /** Assign a native long to global Digits object. */
 _numeric_digits& _numeric_digits::operator=(long prec)
 {
+	long digitsdiff = prec - digits;
 	digits = prec;
-	cln::default_float_format = cln::float_format(prec); 
+	cln::default_float_format = cln::float_format(prec);
+
+	// call registered callbacks
+	std::vector<digits_changed_callback>::const_iterator it = callbacklist.begin(),	end = callbacklist.end();
+	for (; it != end; ++it) {
+		(*it)(digitsdiff);
+	}
+
 	return *this;
 }
 
@@ -2026,6 +2037,13 @@ void _numeric_digits::print(std::ostream &os) const
 }
 
 
+/** Add a new callback function. */
+void _numeric_digits::add_callback(digits_changed_callback callback)
+{
+	callbacklist.push_back(callback);
+}
+
+
 std::ostream& operator<<(std::ostream &os, const _numeric_digits &e)
 {
 	e.print(os);
diff --git a/ginac/numeric.h b/ginac/numeric.h
index 18888315..f2a1adbd 100644
--- a/ginac/numeric.h
+++ b/ginac/numeric.h
@@ -27,6 +27,7 @@
 #include "ex.h"
 
 #include <stdexcept>
+#include <vector>
 
 #include <cln/complex.h>
 
@@ -39,6 +40,12 @@
 
 namespace GiNaC {
 
+/** Function pointer to implement callbacks in the case 'Digits' gets changed.
+ *  Main purpose of such callbacks is to adjust look-up tables of certain
+ *  functions to the new precision. Parameter contains the signed difference
+ *  between new Digits and old Digits. */
+typedef void (* digits_changed_callback)(long);
+
 /** This class is used to instantiate a global singleton object Digits
  *  which behaves just like Maple's Digits.  We need an object rather 
  *  than a dumber basic type since as a side-effect we let it change
@@ -55,11 +62,14 @@ public:
 	_numeric_digits();
 	_numeric_digits& operator=(long prec);
 	operator long();
-	void print(std::ostream &os) const;
+	void print(std::ostream& os) const;
+	void add_callback(digits_changed_callback callback);
 // member variables
 private:
 	long digits;                        ///< Number of decimal digits
 	static bool too_late;               ///< Already one object present
+	// Holds a list of functions that get called when digits is changed.
+	std::vector<digits_changed_callback> callbacklist;
 };