Syntax

An infixOperator is one of:   (a) +   % Integer and real addition; set union;       % string catenation   (b) -   % Integer and real subtraction; set difference   (c) *   % Integer and real multiplication; set intersection   (d) /   % Real division   (e) div   % Truncating integer division   (f) mod   % Modulo   (g) rem   % Remainder   (h) **   % Integer and real exponentiation   (i) <   % Less than   (j) >   % Greater than   (k) =   % Equal   (l) <=   % Less than or equal; subset   (m) >=   % Greater than or equal; superset   (n) not=   % Not equal   (o) and   % And (boolean conjunction)   (p) or   % Or (boolean disjunction)   (q) =>   % Boolean implication   (r) in   % Member of set   (s) not in   % Not member of set   (t) shr   % Shift right   (u) shl   % Shift left   (v) xor   % Exclusive OR

Description

An infix operator is placed between two values or operands to produce a third value. For example, the result of 5 + 7 is 12. In some cases the meaning of the operator is determined by its operands. For example, in "pine" + "apple", the + operator means string catenation while in 5 + 7 it means integer addition. There are also prefix operators (-, + and not), which are placed in front of a single value. See prefix operator. In expressions with several operators, such as 3 + 4 * 5, the precedence rules determine the order in which the operation is done (see precedence for a listing of these rules). In this example, the multiplication is done before the addition, so the expression is equivalent to 3 + (4 * 5). The numerical (integer or real) operators are +, -, *, /, div, mod, and **. All of these except div produce a real result when at least one of their operands is real. If both operands are integers, the result is an integer except in the case of real division (/) which always produces a real result regardless of the operands. The div operator is like real division (/), except that it always produces an integer result, truncating any fraction to produce the nearest integer in the direction of zero. The mod operator is the modulo and the rem operator is the remainder. The sign of the result of mod operator is the same as the sign of the second operand. The rem operator operates like the mod operator in Turing (and in most other languages). It produces the remainder, which is the difference between real division (/) and integer division (div). When both operands are positive, this is the modulo. For example, 14 mod 10 is 4. If one of the operands is negative, a negative answer may result, for example, 7 mod 2 is 1. See also the int and real types. The comparison operators (<, >, =, <=, >=, not=) can be applied to numbers as well as to enumerated types. They can also be applied to strings to determine the ordering between strings (see string type for details). Arrays, records, unions and collections cannot be compared. Boolean values (true and false) can be compared only for equality (= and not=); the same applies to pointer values. Set values can be compared using <= and >=, which are the subset and superset operators. The not= operator can be written as ~=. Strings are manipulated using catenation (+) as well as substring expressions (see substring) and the index function (see index). See also the string type. The operators to combine true/false values are and, or, and => (implication), as well as equality (= and not=). See also the boolean type. The set operators are union (+), intersection (*), set difference (-), subset (<=), superset (>=), and membership (in and not in). See also the set type. The shr (shift right), shl (shift left) and xor (exclusive OR) operators accept and produce natural numbers. See shr, shl, and xor.