Conditional

A condition is a logical (boolean) expression resulting in true or false. Conditions are used in when statements to control flow and in match statements for pattern matching.

Arbitrary Conditional¶

The simplest form is a string that describes the condition in natural language:

when "user is authenticated" then {
  // actions when condition is true
} end

This allows authors to express conditions at the appropriate level of abstraction. The actual implementation of the condition check is left to code generation or manual implementation.

Identifier Conditions¶

Conditions can reference identifiers defined with let:

let isValid = "order.items.count > 0"
when isValid then {
  // actions when valid
} end

Identifiers can be negated:

when !isValid then {
  error "Order must have at least one item"
} end

Numeric Expressions¶

Numeric expressions involve comparisons and arithmetic:

Comparison operators: >, <, >=, <=, ==, !=
Arithmetic operators: +, -, *, /

when "order.total > 100" then {
  // apply discount
} end

Note: In RIDDL, these expressions are typically written as strings that describe the intended logic. The actual parsing and evaluation happens during code generation.

Boolean Expressions¶

Boolean expressions combine conditions using logical operators:

AND: Both conditions must be true
OR: Either condition must be true
NOT: Negates a condition

when "user.isVerified AND order.total > 0" then {
  // process order
} end

Match Expressions¶

The match statement provides pattern matching:

match "orderStatus" {
  case "pending" {
    // handle pending
  }
  case "processing" {
    // handle processing
  }
  case "shipped" {
    // handle shipped
  }
  default {
    // handle unknown status
  }
}

Occurs In¶

Statements - specifically when and match statements

Contains¶

Conditions are leaf elements containing:

String literals describing the condition
Identifier references
Logical operators combining sub-conditions