Fix typos in devdocs on isbitsunion arrays

doc/src/devdocs/isbitsunionarrays.md

@@ -6,8 +6,8 @@ Julia also supports Union types, quite literally the union of a set of types. Cu
 
 ## isbits Union Structs
 
-Julia now includes an optimization wherein "isbits Union" fields in types (`mutable struct`, `struct`, etc.) will be stored inline. This is accomplished by determining the "inline size" of the Union type (e.g. `Union{UInt8, Int16}` will have a size of 16 bytes, which represents the size needed of the largest Union type `Int16`), and in addition, allocating an extra "type tag byte" (`UInt8`), whose value signals the type of the actual value stored inline of the "Union bytes". The type tag byte value is the index of the actual value's type in the Union type's order of types. For example, a type tag value of `0x02` for a field with type `Union{Nothing, UInt8, Int16}` would indicate that an `Int16` value is stored in the 16 bytes of the field in the structure's memory; a `0x01` value would indicate that a `UInt8` value was stored in the first 8 bytes of the 16 bytes of the field's memory. Lastly, a value of `0x00` signals that the `nothing` value will be returned for this field, even though, as a singleton type with a single type instance, it technically has a size of 0. The type tag byte for a type's Union field is stored directly after the field's computed Union memory.
+Julia now includes an optimization wherein "isbits Union" fields in types (`mutable struct`, `struct`, etc.) will be stored inline. This is accomplished by determining the "inline size" of the Union type (e.g. `Union{UInt8, Int16}` will have a size of two bytes, which represents the size needed of the largest Union type `Int16`), and in addition, allocating an extra "type tag byte" (`UInt8`), whose value signals the type of the actual value stored inline of the "Union bytes". The type tag byte value is the index of the actual value's type in the Union type's order of types. For example, a type tag value of `0x02` for a field with type `Union{Nothing, UInt8, Int16}` would indicate that an `Int16` value is stored in the 16 bytes of the field in the structure's memory; a `0x01` value would indicate that a `UInt8` value was stored in the first 8 bytes of the 16 bytes of the field's memory. Lastly, a value of `0x00` signals that the `nothing` value will be returned for this field, even though, as a singleton type with a single type instance, it technically has a size of 0. The type tag byte for a type's Union field is stored directly after the field's computed Union memory.
 
 ## isbits Union Arrays
 
-Julia can now also store "isbits Union" values inline in an Array, as opposed to requiring an indirection box. The optimization is accomplished by storing an extra "type tag array" of bytes, one byte per array element, alongside the bytes of the actual array data. This type tag array serves the same function as the type field case: it's value signals the type of the actual stored Union value in the array. In terms of layout, a Julia Array can include extra "buffer" space before and after it's actual data values, which are tracked in the `a->offset` and `a->maxsize` fields of the `jl_array_t*` type. The "type tag array" is treated exactly as another `jl_array_t*`, but which shares the same `a->offset`, `a->maxsize`, and `a->len` fields. So the formula to access an isbits Union Array's type tag bytes is `a->data + (a->maxsize - a->offset) * a->elsize + a->offset`; i.e. the Array's `a->data` pointer is already shifted by `a->offset`, so correcting for that, we follow the data all the way to the max of what it can hold `a->maxsize`, then adjust by `a->ofset` more bytes to account for any present "front buffering" the array might be doing. This layout in particular allows for very efficient resizing operations as the type tag data only ever has to move when the actual array's data has to move.
+Julia can now also store "isbits Union" values inline in an Array, as opposed to requiring an indirection box. The optimization is accomplished by storing an extra "type tag array" of bytes, one byte per array element, alongside the bytes of the actual array data. This type tag array serves the same function as the type field case: its value signals the type of the actual stored Union value in the array. In terms of layout, a Julia Array can include extra "buffer" space before and after its actual data values, which are tracked in the `a->offset` and `a->maxsize` fields of the `jl_array_t*` type. The "type tag array" is treated exactly as another `jl_array_t*`, but which shares the same `a->offset`, `a->maxsize`, and `a->len` fields. So the formula to access an isbits Union Array's type tag bytes is `a->data + (a->maxsize - a->offset) * a->elsize + a->offset`; i.e. the Array's `a->data` pointer is already shifted by `a->offset`, so correcting for that, we follow the data all the way to the max of what it can hold `a->maxsize`, then adjust by `a->ofset` more bytes to account for any present "front buffering" the array might be doing. This layout in particular allows for very efficient resizing operations as the type tag data only ever has to move when the actual array's data has to move.