Enum Expr 

pub enum Expr {
    Num(i128),
    Label(String),
    Add(Box<Expr>, Box<Expr>),
    Sub(Box<Expr>, Box<Expr>),
}

An expression node for label arithmetic.

Variants

Num(i128)

A numeric literal.

Label(String)

A label reference.

Add(Box<Expr>, Box<Expr>)

Addition: left + right.

Sub(Box<Expr>, Box<Expr>)

Subtraction: left - right.

Implementations

impl Expr

pub fn eval(&self) -> Option<i128>

Try to evaluate to a constant integer.

Returns None if the expression still contains unresolved label references.

pub fn label_addend(&self) -> Option<(&str, i64)>

Decompose into a single label reference plus a numeric addend.

Returns Some((label_name, addend)) when the expression is of the form label, label + const, or label - const (after constant folding). Returns None if the expression has zero or multiple label references, or a negated label (e.g. 5 - label).

pub fn resolve_constants( &mut self, lookup: impl Fn(&str) -> Option<i128> + Copy, )

Replace Expr::Label(name) nodes with Expr::Num(value) when the given lookup returns a value for the name.

Trait Implementations

impl Clone for Expr

fn clone(&self) -> Expr

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Expr

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

Formats the value using the given formatter.

impl Display for Expr

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

Formats the value using the given formatter.

impl PartialEq for Expr

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Expr

impl StructuralPartialEq for Expr