Enum Expression 

pub enum Expression {
    Literal(Length),
    Percentage(Percentage),
    Add(Box<Expression>, Box<Expression>),
    Sub(Box<Expression>, Box<Expression>),
    Mul(Box<Expression>, f64),
    Div(Box<Expression>, f64),
}

Mathematical expression for CSS calc() values

Supports:

• Literals (absolute lengths)
• Percentages (relative to base value)
• Binary operations: +, -, *, /
• Nested expressions

Examples

use fop_types::{Expression, Length, Percentage, expression::EvalContext};

// Parse calc(100% - 20pt)
let expr = Expression::parse("calc(100% - 20pt)").unwrap();

// Evaluate with context
let ctx = EvalContext {
    base_width: Some(Length::from_pt(200.0)),
    base_height: None,
    font_size: Length::from_pt(12.0),
};
let result = expr.evaluate(&ctx).unwrap();
assert_eq!(result, Length::from_pt(180.0));

Variants

Literal(Length)

A literal length value

Percentage(Percentage)

A percentage value (needs base to resolve)

Add(Box<Expression>, Box<Expression>)

Addition of two expressions

Sub(Box<Expression>, Box<Expression>)

Subtraction of two expressions

Mul(Box<Expression>, f64)

Multiplication of expression by scalar

Div(Box<Expression>, f64)

Division of expression by scalar

Implementations

impl Expression

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

Parse a calc() expression from a string

Examples

use fop_types::Expression;

let expr = Expression::parse("calc(100% - 20pt)").unwrap();
let expr2 = Expression::parse("calc(50% + 10mm)").unwrap();
let expr3 = Expression::parse("calc((100% - 40pt) / 2)").unwrap();

pub fn evaluate(&self, context: &EvalContext) -> Result<Length>

Evaluate the expression to a concrete length

Examples

use fop_types::{Expression, Length, expression::EvalContext};

let expr = Expression::parse("calc(100% - 20pt)").unwrap();
let ctx = EvalContext::with_width(Length::from_pt(200.0), Length::from_pt(12.0));
let result = expr.evaluate(&ctx).unwrap();
assert_eq!(result, Length::from_pt(180.0));

Trait Implementations

impl Clone for Expression

fn clone(&self) -> Expression

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 Display for Expression

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

Formats the value using the given formatter.

impl PartialEq for Expression

fn eq(&self, other: &Expression) -> 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 StructuralPartialEq for Expression