1 unstable release
Uses old Rust 2015
0.1.0 | Nov 11, 2017 |
---|
#1570 in Math
Used in simple_jazz
17KB
431 lines
mex a parser/evaluator for simple mathematical expressions, with no dependencies at all. Currently, it supports only a tiny amount of syntax. Here are some valid expressions:
>> 10
10
>> 10 - 3 * 10
-20
>> π = 3.1415926536
3.1415926536
>> 5 * π
15.707963268
And that's it, for now.
It supports the following operators: +
, -
, *
, /
, =
.
But it's easy to add more (by editing the source).
The crate can be used as a binary or a library. The binary is a REPL, where you enter single expressions line by line and get the result given back to you. An example of the library is below:
use mex::parser;
use mex::evaluator;
use mex::evaluator::context;
use mex::evaluator::object;
fn main() {
let input = "2 * x";
let mut parse = parser::Parser::new(input);
let mut context = context::Context::new();
context.set(&String::from("x"), object::Object::Number(13.5));
match parse.parse() {
Ok(node) => {
match evaluator::eval_node_in(node, &mut context) {
Ok(result) => println!("{}", result),
Err(err) => println!("eval error: {:?}", err),
}
}
Err(e) => println!("parse error: {:?}", e),
};
}
In the future, I'd like to add these things:
-
Simple API for simple uses
- e.g.
mex::evaluate("1 + 2")
→3
- e.g.
-
Functions
- e.g.
f(x, y) = x + y
- e.g.
f(2, 3)
→5
- e.g.
-
Customisation / options
- Probably via bitflags
- Things like which operators are allowed, if you're allowed to define variables, etc...
-
Builtins
- e.g.
π
,e
,sin(θ)
- Going back to the last point: builtins should be optional
- e.g.
-
Multiple expressions in one
- e.g.
5 + {1, 2, 3}
→6
,7
, and8
- They would be returned in a hash set, probably
- e.g.
-
Symbolic Expressions
- e.g.
'x = a + b'
(maybe with different delimiters) - Can be either equations (i.e. with equals), or just simple expressions
where
clause- e.g.
'a + b' where a = 2, b = 10
→12
- e.g.
solve ... for
- e.g.
solve 'a = x + b' for x
→'x = a - b'
- e.g.
(solve 'a = x + b' for x) where a = 5, b = 2
→3
- e.g.
solve 'x^2 + 3x + 2' for x
→(x + 1)(x + 2)
- e.g.
- Maybe even integration/differentiation
- e.g.