agri.spray-mix Unreviewed

def spray_mix(area_hectares: float, water_volume_litres_per_hectare: float, product_dose_per_hectare: float, dose_unit: DoseUnit, tank_litres: float) -> SprayMix

DoseUnit = Literal["litres", "kilograms"]

@dataclass(frozen=True)
class TankLoad:
    """What goes into one tank and what it covers."""

    #: area it covers, to 0.0001 ha
    area_hectares: float
    #: total liquid, to 0.001 L
    spray_litres: float
    #: litres or kilograms of product, to 0.001
    product: float
    #: spray less product for a liquid, all of it for a solid
    water_litres: float

@dataclass(frozen=True)
class SprayMix:
    """The whole job."""

    #: full tanks plus a part tank if there is one
    tank_fills: int
    full_tanks: int
    #: the recipe for a full tank, even when the job needs less than one
    full_tank: TankLoad
    #: the last, part-filled tank; null when the job is whole tanks
    partial_tank: Optional[TankLoad]
    #: to 0.001 L
    total_spray_litres: float
    #: to 0.001
    total_product: float

from fune.agri.spray_mix import spray_mix  # agri.spray-mix@^1

import math

from .agri_spray_mix_types import DoseUnit, SprayMix, TankLoad
from .math_round_div import round_div  ← from math.round-div ^1.0.0 · built alongside by fune
from .math_round_float import round_float  ← from math.round-float ^1.0.0 · built alongside by fune


def _scaled(name: str, value: float, decimals: int, low: int, high: int) -> int:
    if isinstance(value, bool) or not isinstance(value, (int, float)) or not math.isfinite(value) or value < low or value > high:
        raise ValueError("%s must be a finite number from %d to %d, received %r" % (name, low, high, value))
    return int(round(round_float(float(value), decimals) * 10**decimals))


def spray_mix(
    area_hectares: float,
    water_volume_litres_per_hectare: float,
    product_dose_per_hectare: float,
    dose_unit: DoseUnit,
    tank_litres: float,
) -> SprayMix:
    """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.
    """
    area = _scaled("areaHectares", area_hectares, 4, 0, 100000)
    rate = _scaled("waterVolumeLitresPerHectare", water_volume_litres_per_hectare, 1, 0, 10000)
    dose = _scaled("productDosePerHectare", product_dose_per_hectare, 3, 0, 100)
    tank = _scaled("tankLitres", tank_litres, 1, 0, 100000)
    if area < 1:
        raise ValueError("areaHectares must be at least 0.0001 hectares")
    if rate < 1:
        raise ValueError("waterVolumeLitresPerHectare must be at least 0.1 litres")
    if tank < 1:
        raise ValueError("tankLitres must be at least 0.1 litres")
    if dose_unit not in ("litres", "kilograms"):
        raise ValueError('unknown doseUnit "%s": use litres or kilograms' % (dose_unit,))
    # A litre of product per litre of spray would leave no room for water.
    if dose_unit == "litres" and dose >= rate * 100:
        raise ValueError("productDosePerHectare must be less than waterVolumeLitresPerHectare for a liquid product")

    spray = area * rate  # litres x 10^5
    tank_spray = tank * 10000  # litres x 10^5
    full_tanks = spray // tank_spray
    remainder = spray - full_tanks * tank_spray

    # A load from its spray volume in litres x 10^5: area = spray / rate,
    # product = spray x dose / (rate x 10^4) in thousandths.
    def load(s: int) -> TankLoad:
        spray_ml = round_div(s, 100, "half-up")
        product = round_div(s * dose, rate * 10000, "half-up")
        return TankLoad(
            area_hectares=round_div(s, rate, "half-up") / 10000,
            spray_litres=spray_ml / 1000,
            product=product / 1000,
            water_litres=(spray_ml - product if dose_unit == "litres" else spray_ml) / 1000,
        )

    return SprayMix(
        tank_fills=full_tanks + (1 if remainder > 0 else 0),
        full_tanks=full_tanks,
        full_tank=load(tank_spray),
        partial_tank=load(remainder) if remainder > 0 else None,
        total_spray_litres=round_div(spray, 100, "half-up") / 1000,
        total_product=round_div(area * dose, 10000, "half-up") / 1000,
    )

Install

fune build

With that line in your source, in a Python project (language python in fune.project), fune build resolves it and its 2 dependencies, pins them in fune.lock, downloads only the Python 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 Python implementation. Install it without the registry with fune add ./agri.spray-mix-1.0.1-python.fune, or fetch it from a terminal with fune pull agri.spray-mix@1.0.1:python.

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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