Move std-rfc into Nushell (#15042)

Move `std-rfc` into Nushell.  `use std-rfc/<submodule>` now works "out-of-the-box"

crates/nu-std/std-rfc/conversions/mod.nu

@@ -0,0 +1,121 @@
+# Convert a Nushell value to a list
+# 
+# Primary useful for range-to-list, but other types are accepted as well.
+# 
+# Example:
+#
+# 1..10 | into list
+export def "into list" []: any -> list {
+  let input = $in
+  let type = ($input | describe --detailed | get type)
+  match $type {
+    range => {$input | each {||}}
+    list => $input
+    table => $input
+    _ => [ $input ]
+  }
+}
+
+# Convert a list of columns into a table
+#
+# Examples:
+#
+# [
+#  ([ 1 2 3 ] | wrap a)
+#  ([ 4 5 6 ] | wrap b)
+#  ([ 7 8 9 ] | wrap c)
+# ] | columns-into-table 
+# => ╭───┬───┬───┬───╮
+# => │ # │ a │ b │ c │
+# => ├───┼───┼───┼───┤
+# => │ 0 │ 1 │ 4 │ 7 │
+# => │ 1 │ 2 │ 5 │ 8 │
+# => │ 2 │ 3 │ 6 │ 9 │
+# => ╰───┴───┴───┴───╯
+#
+# Can roundtrip with `table-into-columns`
+# 
+# ls | table-into-columns | columns-into-table
+# => ╭───┬────────────────────────┬──────┬────────┬────────────────╮
+# => │ # │          name          │ type │  size  │    modified    │
+# => ├───┼────────────────────────┼──────┼────────┼────────────────┤
+# => │ 0 │ into-list.nu           │ file │  378 B │ 40 minutes ago │
+# => │ 1 │ mod.nu                 │ file │   28 B │ 41 minutes ago │
+# => │ 2 │ name-values.nu         │ file │  394 B │ 34 minutes ago │
+# => │ 3 │ record-into-columns.nu │ file │ 1.3 kB │ 27 minutes ago │
+# => ╰───┴────────────────────────┴──────┴────────┴────────────────╯
+export def columns-into-table []: [list<table> -> table] {
+    reduce {|it| merge $it}
+}
+
+# Convert a record, where each value is a list, into a list of columns.
+# { a: [ 1 2 3 ], b: [ 4 5 6 ] } | record-into-columns
+# => ╭───┬───────────╮
+# => │ 0 │ ╭───┬───╮ │
+# => │   │ │ # │ a │ │
+# => │   │ ├───┼───┤ │
+# => │   │ │ 0 │ 1 │ │
+# => │   │ │ 1 │ 2 │ │
+# => │   │ │ 2 │ 3 │ │
+# => │   │ ╰───┴───╯ │
+# => │ 1 │ ╭───┬───╮ │
+# => │   │ │ # │ b │ │
+# => │   │ ├───┼───┤ │
+# => │   │ │ 0 │ 4 │ │
+# => │   │ │ 1 │ 5 │ │
+# => │   │ │ 2 │ 6 │ │
+# => │   │ ╰───┴───╯ │
+# => ╰───┴───────────╯
+# =>
+# This can be especially useful when combined with `columns-into-table`, as in:
+#
+# { a: [ 1 2 3 ], b: [ 4 5 6 ] } | record-into-columns
+# | columns-into-table
+# => ╭───┬───┬───╮
+# => │ # │ a │ b │
+# => ├───┼───┼───┤
+# => │ 0 │ 1 │ 4 │
+# => │ 1 │ 2 │ 5 │
+# => │ 2 │ 3 │ 6 │
+# => ╰───┴───┴───╯
+# =>
+export def record-into-columns []: [record -> list] {
+    items {|key, val| $val | wrap $key}
+}
+
+# Convert/split a table into a list of columns
+#
+# Examples:
+# ls | table-into-columns 
+# => Returns a list of 4 tables, one for each of the `ls` columns
+#
+# Can be roundtripped with `columns-into-table`
+#
+# ls | table-into-columns | columns-into-table
+# => ╭───┬────────────────────────┬──────┬────────┬────────────────╮
+# => │ # │          name          │ type │  size  │    modified    │
+# => ├───┼────────────────────────┼──────┼────────┼────────────────┤
+# => │ 0 │ into-list.nu           │ file │  378 B │ 40 minutes ago │
+# => │ 1 │ mod.nu                 │ file │   28 B │ 41 minutes ago │
+# => │ 2 │ name-values.nu         │ file │  394 B │ 34 minutes ago │
+# => │ 3 │ record-into-columns.nu │ file │ 1.3 kB │ 27 minutes ago │
+# => ╰───┴────────────────────────┴──────┴────────┴────────────────╯
+export def table-into-columns []: [table -> list<table>] {
+    let IN = $in
+    $IN | columns | each {|col| $IN | select $col}
+}
+
+# Assign keynames to a list of values, effectively converting the list to a record.
+#
+# Example:
+#
+# [ 1 2 3 ] | name-values a b c
+# => ╭───┬───╮
+# => │ a │ 1 │
+# => │ b │ 2 │
+# => │ c │ 3 │
+# => ╰───┴───╯
+export def name-values [...names: string]: [list -> record] {
+    let IN = $in
+    0.. | zip $IN | into record | rename ...$names
+}