Constant-fold allowlist registry — ptr_constant_fold

The numeric default-argument validator ptr_arg_numeric() (scalar by default, vector via vector = TRUE) walks the placeholder's default-argument AST against an allowlist of function and constant names. Authors can extend the allowlist with ptr_register_constant_fold() when their placeholder definitions need additional pure operators.

Usage

ptr_register_constant_fold(name, value)

ptr_clear_constant_fold(name = NULL)

ptr_constant_fold_keywords()

Arguments

name: Character scalar function or constant name.
value: Function or numeric constant to bind under name.

Value

ptr_register_constant_fold() and ptr_clear_constant_fold() return invisible(NULL). ptr_constant_fold_keywords() returns a character vector of currently registered names.

Details

Built-in entries seeded at package load:

Arithmetic: -, +, *, /, ^, %%, %/%
Sequence constructors: :, c, seq, seq.int, seq_len, seq_along

Syntactic literals (TRUE, FALSE, NA, NA_integer_, NA_real_, Inf, NaN) are recognised by the walker directly and never need registration. pi resolves through the registry's parent (baseenv()).

Examples

ptr_register_constant_fold("log10", log10)
ptr_arg_numeric()(quote(log10(100)))
#> [1] 2
ptr_clear_constant_fold("log10")