Friday, August 05, 2022

Zero Arguments Methods

In my book Advanced Java Game Programming, I have a sidebar recommending named notation as a work-around for the Java programming language not supporting named arguments.  Here is the example from the book as converted to the Rust programming language:

let game_data = SerializableGameData::new(
  10,  // health
  99,  // wealth
  18); // wisdom

There is a proposal to bring named arguments to Rust but until this proposal is adopted I have started using a new work-around which I am calling "zero arguments methods".  Here is a static function to be converted:

pub fn periodic_savings_needed(
  f: f64,
  r: f64,
  t: f64,
) -> f64 {
  f * r / ((1.0 + r).powf(t) - 1.0)

Here is the equivalent using a zero arguments method:

#[derive(Clone, Copy, Debug)]
pub struct PeriodicSavingsNeeded {
  pub future_value: f64,
  pub interest_rate: f64,
  pub time_periods: f64,

impl PeriodicSavingsNeeded {
  pub fn calculate(&self) -> f64 {
    let f = self.future_value;
    let r = self.interest_rate;
    let t = self.time_periods;
    f * r / ((1.0 + r).powf(t) - 1.0)

Here is how the zero arguments method can be called:

let calculated_value = PeriodicSavingsNeeded {
  future_value:  1_000_000.0,

  interest_rate: 0.12,
  time_periods:  10.0,


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