/Users/garethloy/Musimathics/Musimat1.2/MusimatTutorial/B0400.cpp File Reference

#include "MusimatTutorial.h"

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 MusimatTutorialSection (B0400)

Function Documentation

MusimatTutorialSection ( B0400   )

Definition at line 2 of file B0400.cpp.

        Print("*** B.4 Operator Associativity and Precedence in Musimat ***");
         B.4 Operator Associativity and Precedence in Musimat
         To keep it simple, the Musimat expressions in this book are formatted to obey simple left-to-right 
         evaluation. In fact, the rules are a little more complex because Musimat is basically C++ in 
         sheep's clothing.
         Table B.2 
         Operator Precedence and Associativity  
         Operator                       Associativity           Description                                                             Examples
         ( )                            left to right       grouping                                a * (x+y) == ax + ay
         -                                      right to left           negation                                                                -3 == -1 * 3
         *    /                         left to right           multiplication and division                             a * b, a / b
         %                                      left to right           remainder after integer division                10 % 3 == 1, 12 % 3 == 0
         +    -                         left to right           addition and subtraction                                a + b, a - b
         <   <=   >   >=        left to right           less-than, less-than-or-equal,                  a < b, a <= b
         greater-than, greater-than-or-equal                                                                                    a > b, a >= b
         ==    !=                       left to right           equal, not equal                                                a == b, a != b
         And                            left to right           logical AND                                                             False And False == False
                                                                                                                                                                        False And True == False
                                                                                                                                                                        True And False == False
                                                                                                                                                                        True And True == True
         Or                                     left to right           logical OR                                                              False Or False == False
                                                                                                                                                                        False Or True == True
                                                                                                                                                                        True Or False == True
                                                                                                                                                                        True Or True == True
         =                                      right to left       assignment                                                          a = b, a = b + c
         Associativity of operators is generally left to right, except for assignment and negation. For 
         example the expression a = c = d assigns the value d to c, then assigns c to a, thereby making 
         all three have equal value.
         Table B.2 shows Musimat's simplified operator precedence and associativity in order from 
         highest to lowest. This precedence list is a shortened version derived from C and C++. Since you 
         can't effectively read or write computer programs unless you have memorized these rules of oper-
         ator precedence and associativity, experts recommend that you study these tables while you brush 
         your teeth every night (Press et al. 1988, 23).
         Warning: some expressions that might seem to have self-evident meaning can't be expressed 
         as such in C/C++ and so don't work in Musimat either. Take the expression c > b > a, for exam-
         ple. You'd hope it would test whether b lies between a and c. Alas. Consider this example:
         If (3 > 2 > 1) Print("True") Else Print("False")
         It first evaluates (3 > 2), which it discovers is True, and replaces this expression with the integer 
         1 (which stands for True in C++). It then evaluates the expression ( 1 > 1 ) which is False. Prob-
         ably not what we wanted. This example can be rewritten as follows:
        If (3 > 2 And 2 > 1) 
         which will print True.