Module constraint

Type-level numeric constraints with zero runtime cost.

This module lets you express numeric constraints like “non-negative”, “non-zero”, or “strictly positive” at the type level, with zero runtime overhead after construction.

With these types, your APIs and components can trust that values always satisfy the required numeric constraints. This guarantee leads to designs that are both safer and more self-documenting.

Provided Constraints

The following marker types represent the most common numeric invariants:

• NonNegative: Zero or greater
• NonPositive: Zero or less
• NonZero: Not equal to zero
• StrictlyNegative: Less than zero
• StrictlyPositive: Greater than zero

Each marker can be used with the generic Constrained<T, C> wrapper, where C is the marker type implementing Constraint<T>. Each also provides an associated [new()] constructor for convenience.

See the documentation and tests for each constraint for more usage patterns.

Extending

You can define custom numeric invariants by implementing Constraint<T> for your own zero-sized marker types.

Structs

Constrained

A wrapper enforcing a numeric constraint at construction time.

NonNegative

Marker type enforcing that a value is non-negative (zero or greater).

NonPositive

Marker type enforcing that a value is non-positive (zero or less).

NonZero

Marker type enforcing that a value is non-zero (not equal to zero).

StrictlyNegative

Marker type enforcing that a value is strictly negative (less than zero).

StrictlyPositive

Marker type enforcing that a value is strictly positive (greater than zero).

Enums

ConstraintError

An error returned when a Constraint is violated.

Traits

Constraint

A trait for enforcing numeric invariants at construction time.