valid 0.3.1

Validate custom types by composing primitive validation functions. Use one common API for validating all kind of business rules including aspects of the application state. One common error type for all kind of constraint violations. It is designed to help with error messages that are meaningful to the user of an application.
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//! Property traits
//!
//! This module defines property traits that enable the generic implementation
//! of the [`Validate`] trait of the provided constraints.
//!
//! Property traits are one way to derive an implementation of [`Validate`]
//! trait for a custom type. For example if we have a custom type that
//! represents some kind of decimal number for which we implement the
//! [`HasDecimalDigits`] trait we can use the existing implementation of the
//! [`Validate`] trait for the [`Digits`] constraint and our custom type.
//!
//! [`Digits`]: ../constraint/struct.Digits.html
//! [`HasDecimalDigits`]: trait.HasDecimalDigits.html
//! [`Validate`]: ../trait.Validate.html

/// The checked property of a type.
///
/// This can be property of enums with 2 variants that have a similar meaning to
/// the boolean type, e.g. yes/no, agreed/rejected, open/closed, etc.
pub trait HasCheckedValue {
    /// Returns whether this value represents "checked"
    fn is_checked_value(&self) -> bool;
}

/// The empty property of a type.
///
/// This is usually a property of some kind of container like `String`, `Vec`,
/// `HashSet` or `HashMap`.
pub trait HasEmptyValue {
    /// Returns whether the value is empty
    fn is_empty_value(&self) -> bool;
}

/// The length property of a type.
///
/// This is usually a property of some kind of container like `String`, `Vec`,
/// `HashSet`, `HashMap` or `&[T]`.
pub trait HasLength {
    /// Returns the length of a value
    fn length(&self) -> usize;
}

/// The number of characters property of a type.
///
/// Counts the number of contained characters. The character count may be
/// different from the length if any character occupies more than one byte in
/// memory.
///
/// This is usually a property of a container of `char`s like `String`,
/// `Vec<char>` or `&[char]`
pub trait HasCharCount {
    /// Returns the number of characters.
    fn char_count(&self) -> usize;
}

/// Defines that a type has a zero value.
pub trait HasZeroValue {
    /// Returns whether this value is zero
    fn is_zero_value(&self) -> bool;
}

/// Properties of a decimal number.
pub trait HasDecimalDigits {
    /// Returns the number of integer digits
    ///
    /// These are the digits to the left of the decimal point
    fn integer_digits(&self) -> u64;

    /// Returns the number of fractional digits
    ///
    /// These are the digits to the right of the decimal point
    fn fraction_digits(&self) -> u64;
}

/// Determines whether the given element is part of a value or member of
/// a collection.
///
/// This is usually a property of some kind of container like `String`, `Vec`,
/// `HashSet` or `&[T]`.
pub trait HasMember<A> {
    /// Returns whether the given element is part of this value or a member of
    /// it
    fn has_member(&self, element: &A) -> bool;
}