Module into_r 

Conversions from Rust types to R SEXP.

This module provides the IntoR trait for converting Rust values to R SEXPs.

Submodules

Module	Contents
large_integers	i64, u64, isize, usize → REALSXP, plus string/bool/Option scalars
collections	HashMap, BTreeMap, HashSet, BTreeSet → named/unnamed lists
result	Result<T, E> → list with ok/err fields
altrep	Altrep<T> marker type, Lazy<T> alias, IntoRAltrep trait

Choosing the right outbound conversion

IntoR is the lax outbound path — it silently widens 64-bit integers to R’s REALSXP when the value doesn’t fit INTSXP. The strict alternative lives in crate::strict and is opted into via #[miniextendr(strict)], which routes through crate::strict::checked_into_sexp_i64 and friends. Failure mode of staying on the default lax path when you care about exact representation: an i64 value just above i32::MAX lands in R as an inexact f64 (and IDs/counters larger than 2^53 start colliding).

For storage-directed conversions (e.g. force Vec<i64> into INTSXP when values fit), reach for crate::into_r_as::IntoRAs instead.

The inbound counterpart is crate::from_r::TryFromSexp (strict by construction — returns Result); the inbound looser path is crate::coerce::Coerce / crate::coerce::TryCoerce. There is intentionally no TryFromSexpStrict trait.

Thread Safety

The trait provides two methods:

• IntoR::into_sexp - checked version with debug thread assertions
• IntoR::into_sexp_unchecked - unchecked version for performance-critical paths

Use into_sexp_unchecked when you’re certain you’re on the main thread:

• Inside ALTREP callbacks
• Inside standalone #[miniextendr] functions (they run on the main thread)
• Inside extern "C-unwind" functions called directly by R

The absence contract: what None becomes in R

None does not map to one universal R value — it depends on the shape of T in Option<T>:

• Owned scalars (Option<i32>, Option<f64>, Option<bool>, Option<String>, and friends in large_integers) → the matching NA_<type>_. R has a native NA sentinel for each of these.
• Option<&T> where T: Copy (e.g. Option<&i32>) → NULL. A reference has nothing to copy on None, so there is no NA to produce. See the impl doc on Option<&T> in large_integers.
• Option<&str> is the one exception to the previous rule: it returns NA_character_, matching Option<String>, because str is unsized and can’t use the generic Copy-bounded blanket impl — it has its own hand-written impl instead.
• Containers (Option<Vec<T>>, Option<HashMap<..>>, Option<HashSet<..>>, Option<BTreeMap<..>>, Option<BTreeSet<..>>) → NULL. No container type has a native R NA sentinel either.
• The reading markers’ Option (Option<AsNumeric>, Option<AsNumericVec>, Option<AsCharacter>, Option<AsCharacterVec>; see AsNumeric and AsCharacter) → NULL. NA already means Some(marker(None)), so NULL is what the marker’s Option reads back as None.

Changing a return type from Option<i32> to Option<&i32> or Option<Vec<i32>> therefore silently flips the R-visible absence value from NA_integer_ to NULL, and switching a return from Option<f64> to Option<AsNumeric> changes NA to NULL, with no compiler warning. See result for the analogous (and differently-shaped) contract on Result::Err.

Re-exports

pub use altrep::*;

pub use result::*;

Modules

altrep 🔒

ALTREP marker type (Altrep<T> / Lazy<T>).

collections 🔒

Collection conversions (HashMap, BTreeMap, HashSet, BTreeSet) to R.

large_integers 🔒

Large integer types → REALSXP (f64).

owned_str 🔒

Scalar and vector conversions for owned unsized UTF-8 strings.

result 🔒

Result<T, E> conversions to R.

Macros

impl_into_r_vec_native 🔒

impl_into_r_via_coerce 🔒

Macro for infallible widening IntoR via Coerce.

impl_lossy_string_into_r 🔒

Generate IntoR impls for types with to_string_lossy() (owned scalar, ref scalar, Option, Vec, Vec<Option>). Used for PathBuf/&Path and OsString/&OsStr.

impl_option_collection_into_r 🔒

impl_scalar_into_r 🔒

Macro for scalar IntoR via SEXP::scalar_* methods.

impl_set_coerce_into_r 🔒

Macro for HashSet<T>/BTreeSet<T> where T coerces to i32 (R’s native integer type).

impl_tuple_into_r 🔒

Convert Rust tuples to unnamed R lists, collecting every failing field. Field error types may differ; their messages share the existing batched conversion format with 1-based positions, wrapped in IntoRError::Inner.

impl_tuple_vec_into_r 🔒

impl_vec_coerce_into_r 🔒

Macro for Vec<T> where T coerces to a native R type.

impl_vec_map_into_r 🔒

impl_vec_option_coerce_into_r 🔒

Macro for Vec<Option<T>> where T coerces to a type with existing Option impl.

impl_vec_option_into_r 🔒

Macro for NA-aware Vec<Option<T>> → R vector conversions.

impl_vec_option_logical_into_r 🔒

impl_vec_option_smart_i64_into_r 🔒

Macro for NA-aware Vec<Option<T>> → R smart vector conversion. Checks if all non-None values fit i32 → INTSXP, otherwise REALSXP.

impl_vec_smart_i64_into_r 🔒

into_r_infallible 🔒

Generate an infallible IntoR impl whose only real method is into_sexp.

Traits

IntoR

Trait for converting Rust types to R SEXP values.

IntoRAltrep

Extension trait for ALTREP conversions.

Functions

alloc_r_vector 🔒 ^⚠

Allocate an R vector of type T with n elements and return (SEXP, &mut [T]).

alloc_r_vector_unchecked 🔒 ^⚠

Allocate an R vector (unchecked FFI variant).

logical_iter_to_lglsxp 🔒

Helper: allocate LGLSXP and fill from an i32 iterator (checked).

logical_iter_to_lglsxp_unchecked 🔒 ^⚠

Helper: allocate LGLSXP and fill from an i32 iterator (unchecked).

opt_str_iter_to_strsxp 🔒

Helper: allocate STRSXP and fill from an optional-string iterator (checked).

opt_str_iter_to_strsxp_unchecked 🔒 ^⚠

Helper: allocate STRSXP and fill from an optional-string iterator (unchecked).

str_iter_to_strsxp 🔒

Helper: allocate STRSXP and fill from a string iterator (checked).

str_iter_to_strsxp_unchecked 🔒 ^⚠

Helper: allocate STRSXP and fill from a string iterator (unchecked).

try_vecsxp_from_iter 🔒 ^⚠

Fallible twin of vecsxp_from_iter: stops at the first row whose conversion fails. The list stays protected by the local scope until it returns, so the partially filled list is released on the error path.

try_vecsxp_from_iter_unchecked 🔒 ^⚠

_unchecked twin of try_vecsxp_from_iter — uses ListBuilder::set_unchecked. The caller’s adaptor must produce children via try_into_sexp_unchecked().

vec_of_into_r_to_list 🔒

Helper: convert a Vec of IntoR items to an R list (VECSXP).

vec_of_maps_to_list 🔒

Helper to convert a Vec of map-like types to an R list of named lists.

vec_option_of_into_r_to_list 🔒

Helper: convert Vec<Option<C: IntoR>> to a VECSXP, with None mapping to R_NilValue (NULL) and Some(v) mapping to whatever v.into_sexp() produces.

vec_to_sexp 🔒 ^⚠

Convert a slice to an R vector (checked) using copy_from_slice.

vec_to_sexp_unchecked 🔒 ^⚠

Convert a slice to an R vector (unchecked) using copy_from_slice.

vecsxp_from_iter 🔒 ^⚠

Build a VECSXP from an exact-size iterator of child SEXPs (checked).

vecsxp_from_iter_unchecked 🔒 ^⚠

_unchecked twin of vecsxp_from_iter — uses ListBuilder::set_unchecked. For ALTREP / with_r_thread / unwind contexts. The caller’s adaptor must produce children via into_sexp_unchecked().