Webdoc information on Unicode string literals

docs/src/reference-main-strings.md

@@ -173,6 +173,25 @@ You can use the following backslash escapes for strings such as between the doub
 * `\"`: double quote
 * `\123`: Octal 123, etc. for `\000` up to `\377`
 * `\x7f`: Hexadecimal 7f, etc. for `\x00` up to `\xff`
+* `\u2766`, `\U00010877:`: Unicode literals. For technical reasons, you must supply four hex digits after `\u` and eight hex digits after `\U`.
+
+<pre class="pre-highlight-in-pair">
+<b>mlr repl</b>
+</pre>
+<pre class="pre-non-highlight-in-pair">
+[mlr] "a\nb"
+"a
+b"
+
+[mlr] "a\tb"
+"a	b"
+
+[mlr] "a\x62c"
+"abc"
+
+[mlr] "\u2766\U00010877"
+"❦𐡷"
+</pre>
 
 See also [https://en.wikipedia.org/wiki/Escape_sequences_in_C](https://en.wikipedia.org/wiki/Escape_sequences_in_C).
 

docs/src/reference-main-strings.md.in

@@ -121,6 +121,23 @@ You can use the following backslash escapes for strings such as between the doub
 * `\"`: double quote
 * `\123`: Octal 123, etc. for `\000` up to `\377`
 * `\x7f`: Hexadecimal 7f, etc. for `\x00` up to `\xff`
+* `\u2766`, `\U00010877:`: Unicode literals. For technical reasons, you must supply four hex digits after `\u` and eight hex digits after `\U`.
+
+GENMD-CARDIFY-HIGHLIGHT-ONE
+mlr repl
+[mlr] "a\nb"
+"a
+b"
+
+[mlr] "a\tb"
+"a	b"
+
+[mlr] "a\x62c"
+"abc"
+
+[mlr] "\u2766\U00010877"
+"❦𐡷"
+GENMD-EOF
 
 See also [https://en.wikipedia.org/wiki/Escape_sequences_in_C](https://en.wikipedia.org/wiki/Escape_sequences_in_C).
 

internal/pkg/lib/unbackslash.go

@@ -49,6 +49,10 @@ func UnbackslashStringLiteral(input string) string {
 	//	} else {
 	//		return input
 	//	}
+	//
+	// ... and, given that desire, we don't a priori know how many digits in Unicode
+	// escape sequences -- so we *require* that people use four hex digits after \u
+	// and eight hex digits after \U.
 
 	var buffer bytes.Buffer
 

internal/pkg/parsing/mlr.bnf

@@ -89,8 +89,7 @@ _string_literal_element
   | ( '\\' '[' ) | ( '\\' ']' )
   | ( '\\' 'b' ) | ( '\\' 'f' )
   | ( '\\' 'n' ) | ( '\\' 'r' )
-  | ( '\\' 't' )
-  | ( '\\' 'x' )
+  | ( '\\' 't' ) | ( '\\' 'x' ) | ( '\\' 'a' ) | ( '\\' 'v' )
   | ( '\\' 'u' ) | ( '\\' 'U' )
   | ( '\\' '.' )
   | ( '\\' '*' )

todo.txt

@@ -1,14 +1,12 @@
 =============================================================== RELEASES
 
 * plan 6.1.0
-  ? strptime
-  ? inference
-  ? datediff et al.
+  ? strptime/882
   ? mlr join --left-fields a,b,c
   o fmt/unfmt/regex doc
   o FAQ/examples reorg
   m strptime/strftime tabulate options
-  m unicode string literals
+  k unicode string literals
   k natural sort order
   k IANA-TSV w/ \{X}
   k still need csv --lazy-quotes
@@ -23,8 +21,10 @@
   k ?foo and ??foo @ repl help
   k doc-improves
 * plan 6.2.0
+  ? datediff et al.
   ? rank
   ? YAML
+  ? #908 inferencing options
 
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