[R] %% returns wrong results for decimals and errors for large int64; use the modulo kernel #55334

Describe the bug, including details regarding any error messages, version, and platform.

The R package emulates %% as x - y * (x %/% y), in Ops.ArrowDatum (arrow-datum.R) and Expression$op() (expression.R). The %/% step casts both operands to double, so inputs beyond double precision give wrong answers or fail:

library(arrow)
library(bit64)

# int64 above 2^53: errors
Array$create(as.integer64("9007199254740993")) %% 7L
#> Error: Invalid: Integer value 9007199254740993 not in range: -9007199254740992 to 9007199254740992

# decimal with 20 significant digits: silently wrong
d <- Scalar$create("12345678901234567890.12", string())$cast(decimal128(25, 2))
as.vector(d %% 7L)
#> [1] 722.12
# correct answer is 1.12

Arrow C++ 26.0.0 added modulo and modulo_checked (#46901), floored like R's %% (result takes the sign of the divisor), with native int64 and decimal support. call_function("modulo", ...) gives 5 and 1.12 for the two cases above.

Both code paths should call modulo directly. .operator_map in dplyr-funcs-simple.R has a placeholder entry mapping %% to divide_checked with a comment saying it isn't used; that can go too.

One behaviour to preserve: R returns NA for integer x %% 0L and the current emulation matches that, whereas modulo errors with "divide by zero". The new binding needs an if_else on a zero divisor like the one %/% already has.

Drafted with AI assistance.

Component(s)

R