Macro rule 

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

Define a rewrite rule with pattern/template syntax.

Syntax

rule!(arena, "rule_name", LHS_PATTERN => RHS_TEMPLATE)
rule!(arena, "rule_name", LHS_PATTERN => RHS_TEMPLATE if condition_expr)

• arena — an expression of type &mut Arena.
• "rule_name" — a string literal used for tracing.
• Identifiers ending in _ are wilds (pattern variables): they match any sub-expression and bind it.
• Known constants: pi, E, I, oo, nan, zoo.
• Integer literals: 0, 1, 2, -3, etc.
• Functions: sin, cos, tan, exp, ln, sqrt, abs.
• => separates the pattern (LHS) from the template (RHS).
• An optional if <expr> after the RHS specifies a condition function: fn(&Arena, &Substitution) -> bool.

Examples

use symplex::prelude::*;
use symplex::rule;

let rules = vec![
    rule!(arena, "pythagorean", sin(w_)^2 + cos(w_)^2 => 1),
    rule!(arena, "exp_ln", exp(ln(w_)) => w_),
    rule!(arena, "ln_exp", ln(exp(w_)) => w_),
];

Limitations

• Only wilds (w_), integers, known constants, and known functions are allowed. Bare identifiers that are not wilds or constants produce a compile error.