agri.spray-mix Unreviewed

export function sprayMix(areaHectares: number, waterVolumeLitresPerHectare: number, productDosePerHectare: number, doseUnit: DoseUnit, tankLitres: number): SprayMix

export type DoseUnit = "litres" | "kilograms";

/** What goes into one tank and what it covers. */
export interface TankLoad {
  /** area it covers, to 0.0001 ha */
  readonly areaHectares: number;
  /** total liquid, to 0.001 L */
  readonly sprayLitres: number;
  /** litres or kilograms of product, to 0.001 */
  readonly product: number;
  /** spray less product for a liquid, all of it for a solid */
  readonly waterLitres: number;
}

/** The whole job. */
export interface SprayMix {
  /** full tanks plus a part tank if there is one */
  readonly tankFills: number;
  readonly fullTanks: number;
  /** the recipe for a full tank, even when the job needs less than one */
  readonly fullTank: TankLoad;
  /** the last, part-filled tank; null when the job is whole tanks */
  readonly partialTank: TankLoad | null;
  /** to 0.001 L */
  readonly totalSprayLitres: number;
  /** to 0.001 */
  readonly totalProduct: number;
}

import { sprayMix } from "#fune/agri.spray-mix@^1";

import { roundDiv } from "./math_round_div.ts";  ← from math.round-div ^1.0.0 · built alongside by fune
import { roundFloat } from "./math_round_float.ts";  ← from math.round-float ^1.0.0 · built alongside by fune
import { type DoseUnit, type SprayMix, type TankLoad } from "./agri_spray_mix_types.ts";

function scaled(name: string, value: number, decimals: number, min: number, max: number): number {
  if (typeof value !== "number" || !Number.isFinite(value) || value < min || value > max) {
    throw new RangeError(`${name} must be a finite number from ${min} to ${max}, received ${value}`);
  }
  return Math.round(roundFloat(value, decimals) * 10 ** decimals);
}

/**
 * Tank mix for a sprayer.
 *
 * Area (0.0001 ha), water volume (0.1 L/ha), dose (0.001/ha) and tank
 * (0.1 L) are held as integers, so the job's spray volume is exact and the
 * count of full tanks cannot be thrown by a float: 129.2 ha at 250 L/ha is
 * exactly 19 tanks of 1700 L, where 129.2 x 250 in floating point is
 * 32299.999999999996 and makes it 18 and a sliver.
 */
export function sprayMix(
  areaHectares: number,
  waterVolumeLitresPerHectare: number,
  productDosePerHectare: number,
  doseUnit: DoseUnit,
  tankLitres: number,
): SprayMix {
  const area = scaled("areaHectares", areaHectares, 4, 0, 100000);
  const rate = scaled("waterVolumeLitresPerHectare", waterVolumeLitresPerHectare, 1, 0, 10000);
  const dose = scaled("productDosePerHectare", productDosePerHectare, 3, 0, 100);
  const tank = scaled("tankLitres", tankLitres, 1, 0, 100000);
  if (area < 1) throw new RangeError("areaHectares must be at least 0.0001 hectares");
  if (rate < 1) throw new RangeError("waterVolumeLitresPerHectare must be at least 0.1 litres");
  if (tank < 1) throw new RangeError("tankLitres must be at least 0.1 litres");
  if (doseUnit !== "litres" && doseUnit !== "kilograms") {
    throw new RangeError(`unknown doseUnit "${doseUnit}": use litres or kilograms`);
  }
  // A litre of product per litre of spray would leave no room for water.
  if (doseUnit === "litres" && dose >= rate * 100) {
    throw new RangeError("productDosePerHectare must be less than waterVolumeLitresPerHectare for a liquid product");
  }

  const spray = area * rate; // litres x 10^5
  const tankSpray = tank * 10000; // litres x 10^5
  const fullTanks = Math.floor(spray / tankSpray);
  const remainder = spray - fullTanks * tankSpray;

  // A load from its spray volume in litres x 10^5: area = spray / rate,
  // product = spray x dose / (rate x 10^4) in thousandths.
  const load = (s: number): TankLoad => {
    const sprayMl = roundDiv(s, 100, "half-up");
    const product = roundDiv(s * dose, rate * 10000, "half-up");
    return {
      areaHectares: roundDiv(s, rate, "half-up") / 10000,
      sprayLitres: sprayMl / 1000,
      product: product / 1000,
      waterLitres: (doseUnit === "litres" ? sprayMl - product : sprayMl) / 1000,
    };
  };
  return {
    tankFills: fullTanks + (remainder > 0 ? 1 : 0),
    fullTanks,
    fullTank: load(tankSpray),
    partialTank: remainder > 0 ? load(remainder) : null,
    totalSprayLitres: roundDiv(spray, 100, "half-up") / 1000,
    totalProduct: roundDiv(area * dose, 10000, "half-up") / 1000,
  };
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 2 dependencies, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add agri.spray-mix

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./agri.spray-mix-1.0.1-typescript.fune, or fetch it from a terminal with fune pull agri.spray-mix@1.0.1:typescript.

The whole function, every language, is one file too: agri.spray-mix-1.0.1.fune, 23,979 bytes, sha256 865c75eea05b131780d875c1023f8d889054971285cf0ac22b48355d174d2bda. It installs into a project of any language.

// fune: before agri.spray-mix

// fune: after agri.spray-mix

// fune: replace math.round-div in agri.spray-mix
// fune: replace math.round-float in agri.spray-mix

// fune: step agri.spray-mix after <n|label>

More from the author

## Terms

- **Water volume** (the application rate) is the total spray liquid applied per hectare, product included, as sprayer calibration sets it. - **Dose** is the label rate of product per hectare, in litres for a liquid or kilograms for a solid (`doseUnit`). - **Water** in a tank is the spray volume less the product for a liquid, since the product takes up room; for a solid it is the whole spray volume (the powder or granules dissolve or disperse into it).

## Exactness

Inputs are taken to 0.0001 ha, 0.1 L/ha, 0.001 L or kg per ha and 0.1 L (`math.round-float`) and held as integers, so the job's total spray volume is exact and the full-tank count is a whole-number division. In floating point, 129.2 ha x 250 L/ha is 32299.999999999996, which makes 18 full 1700 L tanks and a sliver; this gives exactly 19.

Each load's area, spray, product and water are worked out from its own spray volume and rounded half up (area to 0.0001 ha, liquids and product to 0.001). Water is the rounded spray less the rounded product, so each load adds up.

## What it does not do

It does not check the dose, water volume, number of applications or buffer zones against the label, account for rinsate, the tank's unusable residue (give the usable capacity) or a tank-mix order, or convert units.

## Limits

Area more than 0 and at most 100,000 ha; water volume 0.1 to 10,000 L/ha; dose 0 to 100 per ha, and for a liquid less than the water volume; tank 0.1 to 100,000 L.

## Before you rely on this

**Not professional advice.** This capability calculates pesticide figures from published rules. It is a software component for developers, not agronomic advice. Rules change and every rate here has an effective date. Check that the dates cover your case. Verify results against the official sources listed above, and have a BASIS-qualified agronomist review how you use it, before anyone relies on the output. Provided "as is" under its licence, without warranty.

**Unreviewed.** This capability's implementations agree in every language and pass its published test vectors, which were worked out from the official sources cited. But no qualified BASIS-qualified agronomist has yet checked those vectors, or confirmed that the capability covers the cases it claims. Treat it as a draft. Do not use it for real people, money or decisions without your own expert review. Once a qualified reviewer signs off, this notice is replaced with their name, qualification and the date. Each new version needs fresh sign-off.

1.0.1 marks it unreviewed. The code and the tests are unchanged.

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