Merge main into function updates

docs/function-parity.md

@@ -1,6 +1,6 @@
 # Function parity: worksheet functions and formulas
 
-> **Last reviewed:** 2026-10-31 · **Last updated:** 2026-10-31 · **Change:** minor (UPPER, LOWER and PROPER use single-character Unicode casing to match measured Excel results; locale check: Windows Excel 16.0 build 20527, LCID 1033) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-31 · **Last updated:** 2026-10-31 · **Change:** minor (UPPER, LOWER and PROPER use single-character Unicode casing to match measured Excel results; locale check: Windows Excel 16.0 build 20527, LCID 1033; earlier: ECMA.CEILING listed with USDOLLAR as not on Microsoft's list; IMSQRT reproduces the stray real part Excel gives for negative reals, and the other IM* differences from Excel are listed; the LAMBDA row lists the recursion limit and its `#NUM!`, and the error a defined name holding an error gives when called; number text with accounting parentheses coerces like Excel 365; INDEX with one index on a 2-D reference is #REF! as in Excel; SUBTOTAL and AGGREGATE cap the cells they visit, #2175) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Excel's worksheet functions, category by category, against GridCraft's function library. Part of
 [target-app-parity.md](target-app-parity.md); gaps feed [gaps.md](gaps.md).
@@ -20,8 +20,8 @@ Excel's worksheet functions, category by category, against GridCraft's function
   evaluator's special forms in `crates/calc/src/eval.rs` (`SPECIAL_FUNCTIONS`: IF, IFS, CHOOSE,
   OFFSET, INDIRECT, INDEX, SUBTOTAL, AGGREGATE, TEXT, LET, LAMBDA, MAP, REDUCE, SCAN, BYROW, BYCOL,
   MAKEARRAY…), excluding the test-only `ADD2`. Every one is an Excel name.
-- **Not on Microsoft's list:** USDOLLAR, a legacy function Excel still evaluates (like DOLLAR),
-  is in our library as a Compatibility function for files that use it. It is not counted above.
+- **Not on Microsoft's list:** USDOLLAR and ECMA.CEILING, legacy functions Excel still evaluates (like DOLLAR),
+  are in our library as Compatibility functions for files that use them. They are not counted above.
 - **Working** excludes stubs that return an error by design: the 7 CUBE functions (`#N/A`, no
   cube connections) and WEBSERVICE and FILTERXML (`#VALUE!`). Excel for Mac also lacks
   WEBSERVICE and FILTERXML; Excel for Windows has them.
@@ -90,6 +90,7 @@ This improves series preparation; it does not change the model-fitting or season
 | LET, LAMBDA, named LAMBDAs, ISOMITTED, MAP/REDUCE/SCAN/BYROW/BYCOL/MAKEARRAY | done. A LAMBDA that calls itself more than 140 times, or a formula nested past the depth limit, gives `#NUM!` (the target app allows deeper recursion, #1581). Calling a defined name that holds an error value gives that error, not `#NAME?` |
 | Iterative calculation for circular references | done: with Enable Iterative Calculation on (`formulas.calculationOptions` `{iterative, maxIterations, maxChange}`, saved as `<calcPr iterate iterateCount iterateDelta>`), loops are evaluated again from their previous values (blank = 0) until no cell on a loop changes by Maximum Change or Maximum Iterations is reached; off, cycles give `#CIRC!`. Set in File › Options › Formulas (Enable iterative calculation, Maximum Iterations 1 to 32767, Maximum Change 0 or more; the two fields are disabled while iteration is off). Differences: GridCraft recalculates on open, so a loop that never settles (`=A1+1`) advances again each time the file is opened
 | 15-significant-digit comparison semantics | done (#57): `=0.1+0.2=0.3` is TRUE, and MATCH and COUNTIF compare the same way. Arithmetic keeps full precision, as Excel does — `=(0.1+0.2)-0.3` is 5.55E-17 |
+| IMSQRT and the other IM* functions against Excel's text | IMSQRT follows Excel's polar route, so a negative real gives Excel's stray real part: `IMSQRT("-4")` is `1.22514845490862E-16+2i` (checked in Excel 16.0 on 79 inputs). Differences kept: IMSQRT of a number with a part above about 1E154 or below about 1E-155 gives the exact root (Excel gives `#NUM!` or 0); IMPOWER, IMEXP, IMSIN, IMCOS, IMSINH and IMCOSH keep exact results where Excel shows the same kind of noise (`IMPOWER("-4",2)` is `16-3.92047505570758E-15i`) or different trailing digits near multiples of pi/2; IMCSC and IMCSCH differ by one unit in the 15th digit; IMARGUMENT returns 16–17 digits where Excel returns 15; the text of IM* and COMPLEX results differs for some magnitudes (Excel writes `COMPLEX(1E-10,1)` as `0.0000000001+i` but `COMPLEX(0.000000123456789012345,1)` as `1.23456789012345E-07+i`, and an integer past 15 digits rounded and zero-padded) |
 | External workbook references (`[Book.xlsx]Sheet1!A1`) | parsed; links dropped on open, no update |
 | Localized function names and `;` separators | **missing** (#45); en-US only |
 | Long flat operator chains (`=A1+A2+…`, `-`, `*`, `/`, `^`, `&`, comparisons) | done: no operand limit below Excel's 8,192-character formula limit (Excel, observed: `=1+1+…` with 4,096 operands is exactly 8,192 characters with the `=` and calculates; one more character is refused). Evaluated (#484), printed (#628), stored, copied, adjusted, saved and reopened without recursing once per operand, on a 1 MiB stack (#916); written to XLSX as plain formulas, not dynamic arrays; Spanish entry accepts them |
@@ -124,6 +125,8 @@ workbooks; results checked in as data, not Excel files) and fixing what it finds
 | Date | Change | Summary |
 |---|---|---|
 | 2026-10-31 | minor | UPPER, LOWER and PROPER use single-character casing: `UPPER("Straße")` keeps ß, `LOWER("İ")` returns i, and `PROPER("İSTANBUL")` returns Istanbul, matching Windows Excel 16.0 build 20527 in LCID 1033 |
+| 2026-10-27 | minor | ECMA.CEILING added to the functions that are in our library but not on Microsoft's list (with USDOLLAR), so the counts don't change |
+| 2026-10-26 | minor | IMSQRT uses Excel's polar route with its cosine reduction, so `IMSQRT("-4")` is `1.22514845490862E-16+2i` as in Excel (exact `2i` before); the rows list the IM* differences still open |
 | 2026-10-25 | minor | LAMBDA row: a LAMBDA that calls itself more than 140 times, and a formula nested past the depth limit, give `#NUM!` (#1809; nesting gave `#CALC!` before). `=Foo(1)` where the defined name Foo holds `#N/A` gives `#N/A`, not `#NAME?` |
 | 2026-10-23 | minor | Number text coercion (VALUE, arithmetic, typed entry): a dollar sign before accounting parentheses (`$(1,234)`, `$ (5)`) and a percent sign after them (`(5)%`) read as negatives; `(-5)`, `((5))`, `($-5)`, `$5%`, `$(5)%` and dates or times in parentheses are `#VALUE!`, as observed in Excel 365 |
 | 2026-10-23 | minor | INDEX with only a row index on a reference of several rows and columns (`INDEX(A1:C3,2)`, `INDEX(A1:C3,0)`) is `#REF!`, as observed in Excel, so it also fails as a range endpoint and inside other functions; an empty column argument (`INDEX(A1:C3,2,)`) still gives the row. Checked that a column array with one index stays a 1×1 array (`TYPE` 64), which is what Excel returns |