> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Dart Logical OR
The `||` (logical OR) operator is a binary boolean operator that evaluates two expressions and returns `true` if at least one of the operands evaluates to `true`. It returns `false` strictly when both operands evaluate to `false`.
```dart theme={"dark"}
expression1 || expression2
```
## Technical Characteristics
* **Strict Type Requirement:** Both operands must evaluate to the `bool` type. Unlike languages with "truthy" or "falsy" concepts (e.g., JavaScript), Dart enforces strict type checking and does not perform implicit type coercion on non-boolean values.
* **Short-Circuit Evaluation:** Dart evaluates the `||` operator using short-circuit logic from left to right. If the left operand evaluates to `true`, the operator immediately yields `true` and the right operand is **never evaluated**.
* **Associativity:** Left-to-right.
* **Precedence:** The `||` operator has lower precedence than the logical AND (`&&`) operator and relational operators (such as `==`, `!=`, `<`), but higher precedence than assignment operators (`=`).
## Evaluation Mechanics
The following demonstrates the standard truth table outcomes:
```dart theme={"dark"}
bool a = true || true; // true
bool b = true || false; // true
bool c = false || true; // true
bool d = false || false; // false
```
## Short-Circuit Behavior
Because of short-circuit evaluation, the right-hand expression is entirely bypassed if the left-hand expression satisfies the `true` condition. This mechanism prevents the execution of functions, state mutations, or potential runtime errors present in the second operand.
```dart theme={"dark"}
bool executeSideEffect() {
print('Right operand evaluated');
return true;
}
void main() {
// The left operand is true, so short-circuiting occurs.
// executeSideEffect() is never called, and nothing is printed.
bool result1 = true || executeSideEffect();
// The left operand is false, so the right operand MUST be evaluated.
// "Right operand evaluated" is printed to the console.
bool result2 = false || executeSideEffect();
}
```
## Strict Boolean Enforcement
Attempting to use non-boolean types with the `||` operator results in a compile-time error. Expressions must be explicitly resolved to `bool`.
```dart theme={"dark"}
// INVALID: Compile-time error
// Error: A value of type 'int' can't be assigned to a variable of type 'bool'.
bool invalid = 1 || 0;
bool invalidString = "text" || "";
// VALID: Explicit boolean expressions are required
bool valid = (1 > 0) || ("text".isNotEmpty);
```
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