Index an ordered sequence

Ordered sequences support read indexing while preserving key-order semantics.

Usage

# S3 method for class 'ordered_sequence'
x[i, ...]

# S3 method for class 'ordered_sequence'
x[[i, ...]]

# S3 method for class 'ordered_sequence'
x[i] <- value

# S3 method for class 'ordered_sequence'
x[[i]] <- value

Arguments

x

An `ordered_sequence`.

i

For `[`, positive integer indices, character names, or logical mask.

...

Unused.

value

Replacement value (unsupported).

Value

For `[`, an `ordered_sequence` subset that preserves key order.

For `[[`, one payload element by scalar integer position or scalar character name.

No return value; always errors because replacement indexing is unsupported.

No return value; always errors because replacement indexing is unsupported.

Details

For `[`: - integer and logical indices must resolve to strictly increasing positions; - character indices are resolved by names and must also be strictly increasing; - duplicates and reordering are rejected.

For `[[`: - accepts scalar integer position or scalar character name and returns the payload element.

Replacement indexing (`[<-`, `[[<-`) is intentionally unsupported.

See also

[\[.flexseq], [\[<-.ordered_sequence], [\[\[<-.ordered_sequence]

Examples

x <- as_ordered_sequence(list("b", "a", "c"), keys = c(2, 1, 3))
x[1:2]
#> <ordered_sequence> size=2 key_type=numeric
#>   preview[2]: {key= num 1 item= chr "a"} | {key= num 2 item= chr "b"}
try(x[c(2, 1)])
#> Error in .ord_assert_positions_strict(idx) : 
#>   Ordered subsetting requires strictly increasing indices (no duplicates or reordering).