fixit

Converts infix tokens to postfix tokens, otherwise known as https://en.wikipedia.org/wiki/Reverse_Polish_notation.

This library does not do parsing or execution of expressions, but only filters/reorders tokens to allow stack-based execution. The (possibly less efficient) alternative to stack-based execution usually involves walking an expression tree.

Example

```rust use fixit::{BinaryOperator, InfixToken, convert};

// Define your own operand: it could be anything. type MyOperand = f32;

// Define your own operator. enum MyBinaryOp { Add, Sub, Mul, Div, }

// Assign a precedence to each operator impl BinaryOperator for MyBinaryOp { fn precedence(&self) -> u8 { match self { MyBinaryOp::Add => 1, MyBinaryOp::Sub => 1, MyBinaryOp::Mul => 2, MyBinaryOp::Div => 2, } } }

type MyInfixToken = InfixToken;

// The incoming expr tokens could have been parsed from a string via a crate like nom or pest. // Parsing an expression like "a + b * c + d" should give: // vec![ // InfixToken::Operand("a"), InfixToken::BinaryOp(MyBinaryOp::Add), InfixToken::Operand("b"), // InfixToken::BinaryOp(MyBinaryOp::Mul), // InfixToken::Operand("c"), InfixToken::BinaryOp(MyBinaryOp::Add), InfixToken::Operand("d") // ] fn example(expr: Vec) { // Convert to postfix. The result will contain: // vec![ // PostfixToken::Operand("a"), // PostfixToken::Operand("b"), // PostfixToken::Operand("c"), // PostfixToken::BinaryOp(MyBinaryOp::Mul), // PostfixToken::BinaryOp(MyBinaryOp::Add), // PostfixToken::Operand("d"), // PostfixToken::BinaryOp(MyBinaryOp::Add) // ] let postfix_tokens = convert(expr);

// We don't aim to provide a full explanation of postfix expressions here, but
// the expression can now be evaluated by iterating over postfix tokens,
// pushing and popping values off a stack.

} ```

License: MIT OR Apache-2.0