Struct SymbolExpression 

pub struct SymbolExpression { /* private fields */ }

An arithmetic expression over symbols, such as AAPL-MSFT or (BTCUSD+ETHUSD)/2, charted as one synthetic series.

Symbols, decimal numbers, +, -, *, /, a leading minus and parentheses are accepted, with the usual precedence; spaces are ignored. A symbol is a run of letters, digits and ., :, _ or !, such as NASDAQ:AAPL, BRK.B or ES1!, that is not a number. The text it formats to is the symbol of its Instrument. At most 256 tokens are accepted to bound recursive parsing and evaluation of user input.

use chrono::{TimeZone, Utc};
use egui_charts::model::Bar;
use egui_charts::services::SymbolExpression;

let spread = SymbolExpression::parse("aapl - msft").unwrap();
assert_eq!(spread.symbols(), ["aapl", "msft"]);
assert_eq!(spread.to_string(), "aapl-msft");

let day = |d| Utc.with_ymd_and_hms(2024, 3, d, 0, 0, 0).unwrap();
let aapl = [Bar::new(day(1), 170.0, 172.0, 169.0, 171.0, 0.0)];
let msft = [Bar::new(day(1), 410.0, 415.0, 405.0, 412.0, 0.0)];
let bars = spread
    .bars(|symbol| match symbol {
        "aapl" => Some(&aapl[..]),
        "msft" => Some(&msft[..]),
        _ => None,
    })
    .unwrap();
assert_eq!((bars[0].open, bars[0].close), (-240.0, -241.0));

Implementations

impl SymbolExpression

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

Parses text, which may also be a lone symbol.

pub fn symbols(&self) -> Vec<&str>

The symbols of the expression, each once, in order of appearance.

pub fn evaluate(&self, value: impl Fn(&str) -> Option<f64>) -> Option<f64>

The value of the expression with each symbol replaced by value(symbol), or None when a symbol has no finite value or any intermediate result is not finite, as after a division by zero.

pub fn bars<'a>( &self, history: impl Fn(&str) -> Option<&'a [Bar]>, ) -> Result<Vec<Bar>, ExpressionError>

The synthetic series from the time-ordered bars history returns for each symbol.

A bar is made for each time at which every symbol has a bar. Its open and close apply the expression to the components’ opens and closes, its high and low to their highs and lows, and the high and low then widen to cover all four results, since a difference or a quotient of highs need not be the highest value. Times whose result is not finite are left out. Volume is zero because the components have no shared traded volume. A symbol without history is an ExpressionError::UnknownSymbol.

Trait Implementations

impl Clone for SymbolExpression

fn clone(&self) -> SymbolExpression

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SymbolExpression

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

Formats the value using the given formatter.

impl Display for SymbolExpression

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

The expression without spaces and with only the parentheses its order needs.

impl PartialEq for SymbolExpression

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for SymbolExpression