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Keep/Drop Function #92

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kg333 merged 12 commits from kg333/tenebrous-dicebot:keep_drop_function into master 2021-09-26 14:05:57 +00:00
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dicebot/src/basic/parser.rs
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@ -31,33 +31,25 @@ enum Sign {
Minus, Minus,
} }
// Parse a dice expression. Does not eat whitespace /// Parse a dice expression. Does not eat whitespace
fn parse_dice(input: &str) -> IResult<&str, Dice> { fn parse_dice(input: &str) -> IResult<&str, Dice> {
// parse main dice expression // parse main dice expression
let (mut input, (count, _, sides)) = tuple((digit1, tag("d"), digit1))(input)?; let (input, (count, _, sides)) = tuple((digit1, tag("d"), digit1))(input)?;
// check for keep expression (i.e. D&D 5E Advantage) // check for keep expression to keep highest dice (2d20k1)
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projectmoon commented 2021-09-17 06:51:15 +00:00
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I think it is better to document what the keep expression actually is here, so tacking on "1dXkY" would be useful.

And since pattern matches are expressions, I think we can rewrite these two match blocks. Something like this:

let (keep, input) = match tuple::<&str, _, (_, _), _>((tag("k"), digit1))(input) {
    // if ok, keep expression is present
    Ok(r) => (r.0, r.1.1),
    // otherwise absent and keep all dice
    Err(_) => ("".to_string(), count)
};

The same should be doable for the drop expression. I think this way you can also get rid of the mut on input, because let in rust is not just a variable assignment. It actually creates a whole new variable binding.

Note: I haven't tested the above, but it should work. Or some variation of it should work.

I think it is better to document what the keep expression actually is here, so tacking on "1dXkY" would be useful. And since pattern matches are expressions, I think we can rewrite these two match blocks. Something like this: ```rust let (keep, input) = match tuple::<&str, _, (_, _), _>((tag("k"), digit1))(input) { // if ok, keep expression is present Ok(r) => (r.0, r.1.1), // otherwise absent and keep all dice Err(_) => ("".to_string(), count) }; ``` The same should be doable for the drop expression. I think this way you can also get rid of the `mut` on input, because `let` in rust is not just a variable assignment. It actually creates a whole new variable binding. Note: I haven't tested the above, but it should work. Or some variation of it should work.
let keep; let (keep, input) = match tuple::<&str, _, (_, _), _>((tag("k"), digit1))(input) {
match tuple::<&str, _, (_, _), _>((tag("k"), digit1))(input) {
// if ok, keep expression is present // if ok, keep expression is present
Ok(r) => { Ok(r) => (r.1.1, r.0),
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projectmoon commented 2021-09-22 19:53:33 +00:00
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Rust supports tuple destructuring in pattern matching, which may be useful here and the other match:

Ok((rest, (_, keep_amount)) => ...

rest being the rest of the input in this case.

Rust supports tuple destructuring in pattern matching, which may be useful here and the other match: ```rust Ok((rest, (_, keep_amount)) => ... ``` `rest` being the rest of the input in this case.
kg333 commented 2021-09-25 02:58:04 +00:00
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Ooh, that's much more human-readable, thanks!

Ooh, that's much more human-readable, thanks!
input = r.0;
keep = r.1.1;
}
// otherwise absent and keep all dice // otherwise absent and keep all dice
Err(_) => keep = count, Err(_) => (input, "")
}; };
// check for drop expression (i.e. D&D 5E Disadvantage) // check for drop expression to drop highest dice (2d20dh1)
let drop; let (drop, input) = match tuple::<&str, _, (_, _), _>((tag("dh"), digit1))(input) {
match tuple::<&str, _, (_, _), _>((tag("d"), digit1))(input) { // if ok, keep expression is present
// if ok, drop expression is present Ok(r) => (r.1.1, r.0),
Ok(r) => {
input = r.0;
drop = r.1.1;
}
// otherwise absent and keep all dice // otherwise absent and keep all dice
Err(_) => drop = "0", Err(_) => (input, "")
}; };
let count: u32 = count.parse().unwrap(); let count: u32 = count.parse().unwrap();