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Appendix C: Operators
 Rapid-Q Documentation by William Yu (c)1999 Appendix C: Operators

# Introduction to Operators

Operators perform mathematical or logical operations on values. They are usually encompassed by an expression. For example, 2 * 8 is a valid expression, and * is an operator operating on values 2 and 8. Rapid-Q can evaluate both INFIX and POSTFIX (RPN) expressions, but if you want to evaluate POSTFIX expressions, you'll need to note the special cases.

Arithmetic operators
Rapid-Q maintains a table of precedence for each operator. The highest precedence operator will always execute before any lower precedence operator. For operators that share the same precedence, the left to right associativity law holds. Expressions enclosed in braces (...) automatically have higher precedence than expressions outside the braces.
 Operation Operator Precedence Description String index [] 1 Returns a character from a stringie. s\$[2]returns the second character in string s\$ Exponentiation ^ 1 Calculates power of a numberie. 2^6is 2 to the power of 6 Negation - 1 Negates a numberie. -99is negative 99 Multiplication * 2 Multiplies 2 numbersie. 2*6is 2 multiplied by 6 Floating-point Division / 2 Divides 2 floating point numbersie. 6.5/2.6is 6.5 divided by 2.6 Integer Division \ 2 Divides 2 integer numbersBefore integer division is performed, operands are rounded to integers. The result is truncated to an integer value.ie. 6\2is 6 divided by 2 Left Bit Shift SHL 2 Shifts bits left by amount specifiedie. 10 SHL 2is number 10 whose bits are shifted 2 bits to the left Right Bit Shift SHR 2 Shifts bits right by amount specifiedie. 10 SHR 2is number 10 whose bits are shifted 2 bits to the right Modulus/Remainder MOD 3 Returns the remainder of the divisionie. 15 MOD 10is 15/10 whose remainder is 5 Inverse Modulus INV 3 Returns the inverse of a number in modulusie. 3 INV 26The inverse of 3 is 9 in 1 (MOD 26) Addition + 4 Add 2 operands (strings included)ie. 3+6is 3 plus 6 = 9ie. "hi"+"world"is "world" appended to "hi" = "hiworld" Addition & 4 Same as using '+' but maintained for compatibility with other BASIC languages, such as VB. Subtraction - 4 Subtracts 2 operands (strings included)ie. 6-3is 6 minus 3 = 3ie. "jello"-"l"is "jello" minus all occurrences of "l" = "jeo"

Relational operators
Relational operators are used to compare 2 values. The result of this comparison is either "true" (nonzero) or "false" (zero). You may assume that "true" equals -1.
 Relation Operator Precedence Description Equality = 5 Tests for equality between 2 operands (strings included)ie. 2=2if 2 equals 2 then "true" else "false" Inequality <> 5 Tests for inequality between 2 operands (strings included)ie. "hello"<>"world"if "hello" is not equal to "world" then "true" else "false" Less than < 5 Tests if operand is less than another (strings included)ie. 2<10if 2 is less than 10 then "true" else "false" Greater than > 5 Tests if operand is greater than another (strings included)ie. "z">"a"if "z" is greater than "a" then "true" else "false" Less than or equal <= 5 Tests if operand is less than or equal to another (strings included)ie. 2<=10if 2 is less than or equal to 10 then "true" else "false" Greater than or equal >= 5 Tests if operand is greater than or equal to another (strings included)ie. 20>=10if 20 is greater than or equal to 10 then "true" else "false"

Logical operators
Logical operators perform tests on multiple relations, bit manipulation, or Boolean operations and return a true (nonzero) or false (zero) value to be used in making a decision.
 Operation Operator Precedence Description Logical complement NOT 6 Returns the complement (inverted bits)ie. NOT -1-1 has all bits set, NOT -1 inverts all bits Conjunction AND 7 Compare corresponding bits in 2 operands and sets the corresponding bit in the result to 1 if both bits are 1.ie. 5 AND 35 AND 3 = 1 since their first bits are set Disjunction (inclusive "or") OR 8 Compares corresponding bits in 2 operands and sets bit to 1 if either one has a corresponding bit set.ie. 5 OR 35 OR 3 = 7 since bits overlap Exclusive "or" XOR 9 Compares corresponding bits in 2 operands and sets bit to 1 if only one of the operands has a corresponding bit set.ie. 5 XOR 35 XOR 3 = 6 since one bit overlaps

INFIX/POSTFIX notation
Expressions, in most languages, are expressed in INFIX notation. Rapid-Q prefers INFIX notation, but can also handle POSTFIX notation with a few special cases.
```      Example INFIX expression:
A = 4 * 7 + (4 - 1)^6
```
INFIX notation is easier to use and understand than POSTFIX notation. In fact, Rapid-Q's POSTFIX notation is a simple side effect, and was not intentional. Please avoid using POSTFIX if possible.
```      Example POSTFIX expression:
A = (4) (7) (*) (4) (1) (-) (6) (^) (+)
```
The 2 expressions should evaluate to 757. As you'll note, when dealing with POSTFIX notation, make sure all operands and operators are enclosed in braces. When dealing with negation, you'll have to do this instead:
```      Example POSTFIX expression w/negation:
A = (5) (0-5) (-)
```
Notice that (0-5) and (-5) return different results.