SparForte - Reference - Basic Assignment and Expressions

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Basic Assignment and Expressions

Values can be assigned in an assignment statement or in a declaration.

The Assignment Statement (:=)

Values are assigned to variables with the assignment statement (:=). Unlike some languages, assignment is not an operator: it cannot be used in an expression.

Some types are "limited". This means they cannot be assigned using the assignment statement.

Primitive Operators

AdaScript expressions can contain the following operators:

uniary: +, -, not
exponentiation: **
arithmetic: +, -, *, /, & (string concatenation), rem (remainder), mod (modulo), and (bitwise and), or (bitwise or), xor (bitwise exclusive or), * (string duplication)
relational: =, /= (not equals), >=, >, <=, <, in, not in
boolean: and, or, xor (exclusive OR)

The bitwise operators are identical to the boolean operators: SparForte choses which to use on the context of the expression.

in and not in test for membership in a range. (In Ada, the range can be a type but under AdaScript types have no bounds.) The range can be an pair of numbers, characters (not strings) or a pair of enumerated items.

=> b := green in red..blue;
=> b := 5 not in 10..20;

in and not in are technically not operators.

Ada: and then and or else not yet implemented. Character ranges not yet implemented.

Expressions and Order of Operations

An expression is a combination of operands and operators used to compute a result value.

Expression operators are evaluated in the following order:

Factors: literals, variables are other values, uniary +, uniary -, subexpressions
Power Terms: **
Terms: /, mod, rem, *, &
Simple Expressions: +, -
Relations: =, /=, >=, >, <=, < in, not in
Boolean Expressions: and, or, xor