feat(expr-ir): Add linear_space

[dangotbanned]

Description

This one started as a plan to expose the linear_space I adapted from np.linspace.
I added that for use in hist, where on main there is currently a dependency on np.linspace.

Show usage

narwhals/narwhals/_plan/arrow/functions.py

Lines 1579 to 1587 in f50278d

	def hist_zeroed_data(
	arg: int | Sequence[float], *, include_breakpoint: bool
	) -> Mapping[str, Iterable[Any]]:
	# NOTE: If adding `linear_space` and `zeros` to `CompliantNamespace`, consider moving this.
	n = arg if isinstance(arg, int) else len(arg) - 1
	if not include_breakpoint:
	return {"count": zeros(n)}
	bp = linear_space(0, 1, arg, closed="right") if isinstance(arg, int) else arg[1:]
	return {"breakpoint": bp, "count": zeros(n)}

narwhals/narwhals/_plan/arrow/expr.py

Lines 742 to 749 in f50278d

	lower: NativeScalar = fn.min_(native)
	upper: NativeScalar = fn.max_(native)
	if lower.equals(upper):
	# All data points are identical - use unit interval
	rhs = fn.lit(0.5)
	lower, upper = fn.sub(lower, rhs), fn.add(upper, rhs)
	bins = fn.linear_space(lower.as_py(), upper.as_py(), bin_count + 1)
	data = fn.hist_bins(native, bins, include_breakpoint=include)

narwhals/narwhals/_arrow/series.py

Lines 1161 to 1171 in c119546

	def _linear_space(
	self,
	start: float,
	end: float,
	num_samples: int,
	*,
	closed: Literal["both", "none"] = "both",
	) -> _1DArray:
	from numpy import linspace # ignore-banned-import
	return linspace(start=start, stop=end, num=num_samples, endpoint=closed == "both")

However, after l'd ported the polars.linear_space tests and noticing the direct comparison to np.linspace - I got ... curious
So I did my digging and found the polars rust impl - which was a lot cleaner in handling ClosedInterval. So, I stole that instead 😄

I'm deferring support on these for now:

• num_sumples: IntoExprColumn
  • Can add that later (if needed)
  • Mentioning it as polars.linear_space docs have an example with num_samples=pl.len() which seems useful
• {start,end}: TemporalLiteral (and temporal expressions)
  • The Time case will work similarly to Date in (feat(expr-ir): Add date_range, support {date,int}_range(eager=...) #3294)
  • Date and Datetime I don't wanna think about

Related issues

• Child of feat(expr-ir): Finish* implementing ArrowExpr #3325
• Mostly reusing stuff from feat(expr-ir): Add date_range, support {date,int}_range(eager=...) #3294