Macro expr 

expr!() { /* proc-macro */ }

Creates an expression at compile time.

This macro allows you to parse expressions during compilation, which provides better performance and catches syntax errors early.

Examples

use std::collections::HashMap;
use expression_macro::expr;

let expr = expr!("sin(x) + cos(y)");

let mut vars = HashMap::new();
vars.insert("x".to_string(), 0.0);
vars.insert("y".to_string(), 0.0);

let result = expr.evaluate(&vars).unwrap();
assert_eq!(result, 1.0);

Errors

If the expression contains syntax errors, compilation will fail with appropriate error messages.

Supported Syntax

Operators

• Addition: +
• Subtraction: -
• Multiplication: *
• Division: /
• Exponentiation: ^

Functions

• Trigonometric: sin, cos, tan
• Inverse trigonometric: arcsin, arccos, arctan

Other Features

• Parentheses for grouping: (expression)
• Variables: any alphabetic identifier
• Number literals: both integers and floating-point

Technical Details

This macro uses the tokenizer and parser from the expression_core crate to parse the expression string at compile time and generate equivalent Rust code. The output is an Expression object that can be evaluated with different variable values.