Enum Expression 

pub enum Expression {
    Column(ColumnName),
    Number(NumberLiteral),
    Negate(Box<Expression>),
    Binary {
        op: BinaryOp,
        left: Box<Expression>,
        right: Box<Expression>,
    },
}

Arithmetic over the columns of one table, evaluated per row.

Variants

Column(ColumnName)

A column of the table.

Number(NumberLiteral)

A numeric literal.

Negate(Box<Expression>)

Unary minus.

Binary

left op right.

Fields

op: BinaryOp

The operator.

left: Box<Expression>

The left operand.

right: Box<Expression>

The right operand.

Implementations

impl Expression

pub fn parse(input: &str) -> Result<Self, ExpressionError>

Parse input. A lone column name gives Expression::Column.

pub fn as_column(&self) -> Option<&ColumnName>

The column, when the expression is a plain column.

pub fn columns(&self) -> Vec<&ColumnName>

Every column the expression reads, once each, in order of appearance.

Trait Implementations

impl Clone for Expression

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Expression

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Expression

fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error>

Deserialize this value from the given Serde deserializer.

impl Display for Expression

The canonical text: single spaces around binary operators, and parentheses only where the tree needs them (a right operand at the same precedence keeps them, since the operators associate left). A negated negation is - -a: the space keeps -- out of the text, and no parentheses means the text nests no deeper than the tree is tall, so every parsed tree renders to text the parser accepts.

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Expression

impl From<ColumnName> for Expression

fn from(column: ColumnName) -> Self

Converts to this type from the input type.

impl FromStr for Expression

type Err = ExpressionError

The associated error which can be returned from parsing.

fn from_str(input: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

impl Hash for Expression

A plain column hashes as the ColumnName it is, so an aggregate written before expressions keeps its content hash. Anything else hashes its canonical text, which is never a column name: it holds an operator, or is a number, and a column name never starts with a digit.

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Expression

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for Expression

fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Expression