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Operators.md

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title Operators
parent Reference Section
nav_order 4
has_toc false
permalink /Reference/Operators

Operators

Operators built into the twinBASIC language. They are understood by the compiler and are not declared or defined in the runtime library.

Arithmetic

  • + -- addition; with String operands, concatenation
  • - -- subtraction; as a unary operator, negation
  • * -- multiplication
  • / -- floating-point division
  • \ -- integer division (truncating)
  • Mod -- divides two numbers and returns only the remainder
  • ^ -- exponentiation

Concatenation

  • & -- forces string concatenation, regardless of operand types

Comparison

  • Comparison operators (=, <>, <, <=, >, >=) -- numeric or string comparison
  • Like -- wildcard / pattern-matching comparison
  • Is -- compares two object references for identity
  • IsNot -- (twinBASIC) the logical inverse of Is

Bitwise

Both operands are always evaluated. Booleans are treated as integers: True = -1, False = 0.

  • And -- bitwise conjunction
  • Or -- bitwise disjunction
  • Not -- bitwise negation
  • Xor -- bitwise exclusive-or
  • Eqv -- bitwise equivalence
  • Imp -- bitwise implication

Logical Short-Circuit

The right operand is evaluated only when the left operand does not already determine the result.

  • AndAlso -- (twinBASIC) short-circuit conjunction; evaluates the right operand only if the left is True
  • OrElse -- (twinBASIC) short-circuit disjunction; evaluates the right operand only if the left is False

Bitshift

(twinBASIC) Shifts are logical --- vacated bits are filled with zero, and shifts past the operand's width yield 0 rather than wrapping.

  • << -- (twinBASIC) shifts a numeric value left by a given number of bits
  • >> -- (twinBASIC) shifts a numeric value right by a given number of bits

Object Identity

  • Is -- compares two object references for identity
  • IsNot -- (twinBASIC) the logical inverse of Is

Compound Assignment

(twinBASIC) For most arithmetic, concatenation, and bitshift operators, twinBASIC provides a compound form op= that combines the operation with assignment. x op= y is equivalent to x = x op y, but evaluates the left-hand side only once and is a statement rather than an expression.

Operator Compound form Equivalent to
+ += x = x + y
- -= x = x - y
* *= x = x * y
/ /= x = x / y
\ \= x = x \ y
^ ^= x = x ^ y
& &= x = x & y
<< <<= x = x << y
>> >>= x = x >> y

There is no compound form for Mod, or for any of the logical / comparison operators.

Function Pointers

  • AddressOf -- produces a typed function-pointer to a procedure

Operator Precedence

When several operations occur in an expression, each part is evaluated in a fixed order. Arithmetic operators are evaluated first, comparison operators next, and logical operators last. Parentheses override the default order.

Within each category, the order from highest to lowest precedence is:

Arithmetic Comparison Logical
Exponentiation (^) Equality (=) Not
Unary negation (-) Inequality (<>) And, AndAlso
Multiplication and division (*, /) Less than (<) Or, OrElse
Integer division (\) Greater than (>) Xor
Modulus (Mod) Less than or equal to (<=) Eqv
Addition and subtraction (+, -) Greater than or equal to (>=) Imp
String concatenation (&) Like, Is, IsNot
Bitshift (<<, >>)

Comparison operators all have equal precedence and evaluate left-to-right. Multiplication and division also evaluate left-to-right when they appear together, as do addition and subtraction. The & operator is not strictly arithmetic, but in precedence it follows all arithmetic operators and precedes all comparison operators.

The compound-assignment operators (+=, -=, *=, /=, ^=, &=, <<=, >>=) appear only at statement level --- they are not part of any expression, so they do not participate in precedence.