00001 #include "MusimatTutorial.h" 00002 MusimatTutorialSection(B0113) { 00003 Print("*** B.1.13 Type Promotion and Type Coercion ***"); 00004 /***************************************************************************** 00005 00006 B.1.13 Type Promotion and Type Coercion 00007 00008 What if the values in an expression are not of the same type? For example, since both operands 00009 in the expression 2/3 are integers, the quotient will be an integer. The quotient of 4.5/2.25 will 00010 be a real number because both operands are reals. But what is the quotient of 2/2.25? Our options 00011 are to coerce the numerator to be a Real and then perform real division, or coerce the denominator 00012 to be an Integer and then perform integer division. Which shall it be? 00013 00014 Since the set of all reals includes the set of all integers, it makes sense to promote the integer 00015 2 to the corresponding real value 2.0 and then perform real division. Musimat automatically con- 00016 verts 2/2.25 into 2.0/2.25 and then performs real division. In general, integer values are auto- 00017 matically promoted to reals wherever they occur in an expression with reals. 00018 00019 If automatic type promotion is not desired, the type of an expression can be coerced by directly 00020 indicating its type. Consider the expression: 00021 *****************************************************************************/ 00022 00023 Print( 10/Integer(3.33) ); 00024 00025 /***************************************************************************** 00026 First, the real value 3.33 is truncated to the integer value 3, then because both numerator and 00027 denominator are now integers, integer division is performed. Beware of things being done for you 00028 automatically by computers! You still must pay attention to head off unintended consequences. 00029 Consider: 00030 *****************************************************************************/ 00031 00032 Print( 26/Integer(2.5) ); 00033 00034 /***************************************************************************** 00035 prints 13, but 00036 *****************************************************************************/ 00037 00038 Print( Integer(26/2.5) ); 00039 00040 /***************************************************************************** 00041 prints 10. 00042 *****************************************************************************/ 00043 } 00044 00045 00047 /* $Revision: 1.2 $ $Date: 2006/09/05 06:32:25 $ $Author: dgl $ $Name: $ $Id: B0113.cpp,v 1.2 2006/09/05 06:32:25 dgl Exp $ */ 00048 // The Musimat Tutorial � 2006 Gareth Loy 00049 // Derived from Chapter 9 and Appendix B of "Musimathics Vol. 1" � 2006 Gareth Loy 00050 // and published exclusively by The MIT Press. 00051 // This program is released WITHOUT ANY WARRANTY; without even the implied 00052 // warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 00053 // For information on usage and redistribution, and for a DISCLAIMER OF ALL 00054 // WARRANTIES, see the file, "LICENSE.txt," in this distribution. 00055 // "Musimathics" is available here: http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=10916 00056 // Gareth Loy's Musimathics website: http://www.musimathics.com/ 00057 // The Musimat website: http://www.musimat.com/ 00058 // This program is released under the terms of the GNU General Public License 00059 // available here: http://www.gnu.org/licenses/gpl.txt 00060
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