# std.collections > Reflected API reference for the Sema standard-library module std.collections. > Generated by `sema doc` from `stdlib/sema/collections.sema`. Import with `from std.collections import …`. For a narrative introduction see [std.collections](/stdlib/collections/). # `collections` std.collections — small pure helpers used across the standard library. Part of the Sema standard library, written in Sema and shipped with the compiler (embedded via crates/sema-runtime/src/stdlib.rs). Import with `from std.collections import join_str, r6, ...`. # `def r6` ```sema def r6(x: f64) -> f64 !{} ``` **Parameters** | name | type | |---|---| | `x` | `f64` | **Returns** `f64` **Effects** `!{}` # `def join_str` ```sema def join_str(xs: list[str], sep: str) -> str !{} ``` **Parameters** | name | type | |---|---| | `xs` | `list[str]` | | `sep` | `str` | **Returns** `str` **Effects** `!{}` # `def join_ints` ```sema def join_ints(xs: list[int], sep: str) -> str !{} ``` **Parameters** | name | type | |---|---| | `xs` | `list[int]` | | `sep` | `str` | **Returns** `str` **Effects** `!{}` # `def join_floats` ```sema def join_floats(xs: list[f64], sep: str) -> str !{} ``` **Parameters** | name | type | |---|---| | `xs` | `list[f64]` | | `sep` | `str` | **Returns** `str` **Effects** `!{}` # `def dedup_ints` ```sema def dedup_ints(xs: list[int]) -> list[int] !{} ``` **Parameters** | name | type | |---|---| | `xs` | `list[int]` | **Returns** `list[int]` **Effects** `!{}`