Crate ripin 

This library provide a way to evaluate Reverse Polish Notated expressions for numbers and basic evaluators.

Floats and signed integers has already been implemented with basic evaluators (cf. +, -, *, /, neg, pow…).

Of course you can build your own Evaluators by implementing the Evaluate Trait, the only constraint is the compatibility with the Operand type, that can be everything you want (cf. letters, Enums, chinese symbols…).

Expression Usage

Let’s define an expression:

let expr = "3 4 + 2 *"; // (3 + 4) * 2

Tokenize it:

let tokens = expr.split_whitespace();

Ripin can evaluate floating-point expressions:

use ripin::evaluate::FloatExpr;

let expr = FloatExpr::<f32>::from_iter(tokens).unwrap();
assert_eq!(expr.evaluate(), Ok(14.0));

like integers ones:

use ripin::evaluate::IntExpr;

let expr = IntExpr::<i32>::from_iter(tokens).unwrap();
assert_eq!(expr.evaluate(), Ok(14));

Variable Expression Usage

You need variable expressions ? No problem Ripin can do this too !

Declare some variables:

let variables = vec![3.0, 500.0];

Once variables as been set, do the same as before:

use ripin::evaluate::VariableFloatExpr;
use ripin::variable::IndexVar;

let expr = "3 4 + 2 * $0 -"; // (3 + 4) * 2 - $0

let tokens = expr.split_whitespace();
let expr = VariableFloatExpr::<f32, IndexVar>::from_iter(tokens).unwrap();

Evaluate the expression with informations about the way of indexation (usize):

assert_eq!(expr.evaluate_with_variables(&variables), Ok(11.0));

Modules

convert_ref

TryFrom/Into_ref conversion module

evaluate

Evaluate Trait and default Evaluators.

expression

Operation on expressions and Expression construction methods.

variable

Useful structs to use variables with expressions

Structs

Stack

A growable stack implementing push/pop actions.

Functions

pop_two_operands

Removes the last two elements from a stack and return them, or None if there is not enough element.