Pow ^ does not compile when using unchained

[arkanoid87]

import unchained
import measuremancer

let
    a = 2.1.m ± 0.5.m
    b = 1.2.m ± 0.3.m

echo a**b

measuremancer.nim(312, 17) Error: type mismatch: got <Meter, Meter>
but expected one of:
func pow(x, y: float32): float32
  first type mismatch at position: 1
  required type for x: float32
  but expression 'a.val' is of type: Meter
func pow(x, y: float64): float64
  first type mismatch at position: 1
  required type for x: float64
  but expression 'a.val' is of type: Meter

[arkanoid87]

Speaking of power operator, I think there should also be this version

proc `**`*[T: FloatLike](m: FloatLike, p: Measurement[T]): Measurement[T] =`

[arkanoid87]

actually, it doesn't work even without units

import unchained
import measuremancer

let
    u = 2.1 ± 0.5
    z = 1.2 ± 0.3

echo u**z

measuremancer.nim(315, 31) Error: type mismatch: got <float>
but expected one of:
func log[T: SomeFloat](x, base: T): T
  first type mismatch at position: 2
  missing parameter: base

math.log wants second base argument
https://nim-lang.org/docs/math.html#log%2CT%2CT

[arkanoid87]

I need to add that the more I read the code (to hopefully grasp how to create a PR) the more I understand the complexity of unchained integration.

[arkanoid87]

I've been following the white rabbit until I've decided to properly turn it into tests
#8

[arkanoid87]

I'm trying some fixes in my fork a5f0689#diff-c3e2bf281e6b65db974cf236911d68cb47f1f0a14bb0029e5354e573fc2da0eb

I fixed power & exponentials when not using unchained (comparing results with vs python uncertainties), but how to deal with float exponents?

Python Pint handles them at runtime using strings

from pint import UnitRegistry

ureg = UnitRegistry()

distance = 24.0 * ureg.meter
print(repr(distance ** 12.5))
print(repr(distance ** distance))

Unchained hates this to live at compile life

<Quantity(1.78912433e+17, 'meter ** 12.5')>
Traceback (most recent call last):
pint.errors.DimensionalityError: Cannot convert from 'meter' to 'dimensionless'

import unchained

echo pow(5.m, 4.2)

Error: type mismatch: got <Meter, float64>
but expected one of:
func pow(x, y: float32): float32
  first type mismatch at position: 1
  required type for x: float32
  but expression 'm(5)' is of type: Meter
func pow(x, y: float64): float64
  first type mismatch at position: 1
  required type for x: float64
  but expression 'm(5)' is of type: Meter

expression: pow(m(5), 4.2)

should I consider units as base or exponent of power/exponential a compile error?

[Vindaar]

Float based exponents simply don't make sense with units attached! What's a 5.kg^{2.3} ? The same is true for trigonometric functions. Their argument must be UnitLess (or an equivalent like Rad).

Haven't had time to properly look yet, sorry.

[arkanoid87]

No need to be sorry, you wrapped up an amazing system. I just need some time to wrap my head around all of this

[Vindaar]

Closing this, as it should be addressed in version v0.2.2. Feel free to reopen if I missed something.