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+ ++Mup also supports more general "if" clauses. If you happen to be +familiar with the preprocessors for the C and C++ programming +languages, Mup "if" clauses are very similar. +If you're not, that's okay, since things are explained below. +Also, some of the operations are really very rarely needed, so if +you find some of them confusing, you just can skip past this section; +you'll likely never have a need for the complicated operations anyway. +
+
+The general form is
+
+if condition then Mup statements else Mup statements endif +
+One form of "if" is really just a variation of ifdef. It uses the
+keyword "defined" followed by a macro name. So
+
+ ifdef DUET +
+ if defined DUET then +
+ if defined(DUET) then +
+The ! is used to mean "not," so
+
+ ifndef TRIO +
+ if ! defined(TRIO) then +
+So far, this just looks longer, so what's the advantage?
+The difference is that ifdef and ifndef can only be used to check if a single
+macro is defined or not, whereas the "if" condition is much more general,
+and therefore much more powerful.
+Decisions can be based on the values of macros, not just whether they are
+defined or not, and can also be based on more than one macro at a time,
+Here is an example of a condition based on several macros at once:
+
+ if defined(FULL_SCORE) && defined(TRANSPOSE_UP) && ! defined(MIDI) then +
+ if defined(CELLO) || defined(STRINGBASS) +
+The condition can also include numbers and macros used as numeric values
+in arithmetic and comparisons. For example,
+
+ define STAFFS 3 @ + define S 5 @ + if STAFFS > 5 then + // ... this would not be executed, since 3 is not greater than 5 + endif + if 2 <= STAFFS then + // ... This would be executed, since 2 is less than or equal to 3 + endif + if STAFFS + 1 == S - 1 then + // ... This would be executed, since 3+1 equals 5-1 + endif +
| < | less than | +
| > | greater than | +
| <= | less than or equal | +
| >= | greater than or equal | +
| == | equal | +
| != | not equal | +
+Note that the values in the conditions can only be either literal numbers +or macros whose values evaluate to a number. They cannot be things like +Mup parameters. +A macro which is not defined is treated as having a value of zero. +Macro values are substituted for macro names just as elsewhere in Mup, +so if you use a macro whose resulting value does not evaulate to a number, +you may get an error or other unexpected result. +
++If you are familiar with "octal" and "hexadecimal" numbers, they can be +used, following the C language convention of a leading zero for octal +or a leading 0x for hexadecimal. (If you're not familiar with these +numbers or conventions, don't worry about it; it's never really necessary +to use them. Just make sure you don't accidentally start a number other +than a zero with a zero). +
++Values are limited to 32-bit signed numbers. (If you don't know +what that means, all you need to know is that you +can only use numbers between -2147483648 and 2147483647. +
+
+Before we introduce the remaining operators, it would be good to discuss
+two concepts, called precedence and associativity. These determine the
+order in which operations are done. Consider the following expression:
+
+ 5 + 3 * 8 +
+ 5 + (3 * 8) +
+If you really intended the 64 meaning, that could be shown by parentheses,
+indicating you want the addition to be done first:
+
+ (5 + 3) * 8 +
+Associativity determines whether operators of equal precedence are done
+left to right or right to left. Parentheses and
+all of the operators that have two
+operands associate left to right, while all the others
+associate right to left. For example, since addition and subtraction
+associate left to right, the expression
+
+ 10 - 6 - 1 +
+Since the "not" operator and unary minus associate right to left,
+in the expression
+
+ ! - (5) +
+The operators are listed below. Those on the same line have the same +precedence, with those on each line having higher precedence than the +lines below. +
| operators | operations | associativity | +
| ( ) | grouping | left to right | +
| ! ~ - + | not, one's complement, unary minus, unary plus | right to left | +
| * / % | multiply, divide, modulo | left to right | +
| + - | add, subtract | left to right | +
| << >> | left shift, right shift | left to right | +
| < <= > >= | less than, less or equal, greater than, greater or equal | left to right | +
| == != | equal, not equal | left to right | +
| & | bitwise AND | left to right | +
| ^ | bitwise XOR | left to right | +
| | | bitwise OR | left to right | +
| && | logical AND | left to right | +
| || | logical OR | left to right | +
| ? : | interrogation | right to left | +