package liquidsoap-lang

  1. Overview
  2. Docs
Legend:
Page
Library
Module
Module type
Parameter
Class
Class type
Source

Source file builtins_string.ml

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
let string =
  Lang.add_builtin "string" ~category:`String
    ~descr:"Return the representation of a value."
    [
      ( "fields",
        Lang.bool_t,
        Some (Lang.bool false),
        Some "Show toplevel fields around the value." );
      ("", Lang.univ_t (), None, None);
    ]
    Lang.string_t
    (fun p ->
      let show_fields = Lang.to_bool (List.assoc "fields" p) in
      let v = List.assoc "" p in
      let dv = Lang.demeth v in
      (* Always show fields for records. *)
      let show_fields = if Value.is_unit dv then true else show_fields in
      let v = if show_fields then v else dv in
      match v with
        | String { value = s } -> Lang.string s
        | v -> Lang.string (Value.to_string v))

let _ =
  Lang.add_builtin "^" ~category:`String ~descr:"Concatenate strings."
    [("", Lang.string_t, None, None); ("", Lang.string_t, None, None)]
    Lang.string_t
    (fun p ->
      let s1 = Lang.to_string (Lang.assoc "" 1 p) in
      let s2 = Lang.to_string (Lang.assoc "" 2 p) in
      Lang.string (s1 ^ s2))

let _ =
  Lang.add_builtin ~base:string "digest" ~category:`String
    ~descr:"Return an MD5 digest for the given string."
    [("", Lang.string_t, None, None)]
    Lang.string_t
    (fun p ->
      let data = Lang.to_string (List.assoc "" p) in
      Lang.string Digest.(to_hex (string data)))

let _ =
  Lang.add_builtin ~base:string "concat" ~category:`String
    ~descr:"Concatenate strings."
    [
      ("separator", Lang.string_t, Some (Lang.string ""), None);
      ("", Lang.list_t Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let sep = Lang.to_string (List.assoc "separator" p) in
      let l = Lang.to_list (List.assoc "" p) in
      let l = List.map Lang.to_string l in
      Lang.string (String.concat sep l))

let split ~encoding s =
  let buf = Buffer.create 1 in
  let to_string add c =
    Buffer.clear buf;
    add buf c;
    Buffer.contents buf
  in
  let get =
    match encoding with
      | `Ascii -> fun pos -> (to_string Buffer.add_char (String.get s pos), 1)
      | `Utf8 ->
          fun pos ->
            let d = String.get_utf_8_uchar s pos in
            if not (Uchar.utf_decode_is_valid d) then
              failwith "Decoding failed!";
            ( to_string Buffer.add_utf_8_uchar (Uchar.utf_decode_uchar d),
              Uchar.utf_decode_length d )
  in
  let len = String.length s in
  let rec f chars pos =
    if pos = len then List.rev chars
    else (
      let char, len = get pos in
      f (char :: chars) (pos + len))
  in
  f [] 0

let default_encoding = ref `Utf8

let encoding_option =
  ( "encoding",
    Lang.nullable_t Lang.string_t,
    Some Lang.null,
    Some
      "Encoding used to split characters. Should be one of: `\"utf8\"` or \
       `\"ascii\"`" )

let get_encoding p =
  match Lang.to_valued_option Lang.to_string (List.assoc "encoding" p) with
    | None -> ("utf8", !default_encoding)
    | Some "utf8" -> ("utf8", `Utf8)
    | Some "ascii" -> ("ascii", `Ascii)
    | _ ->
        Runtime_error.raise ~pos:(Lang.pos p) ~message:"Invalid encoding!"
          "invalid"

let _ =
  Lang.add_builtin ~base:string "chars" ~category:`String
    ~descr:"Split string into characters. Raises `error.invalid` on errors."
    [encoding_option; ("", Lang.string_t, None, None)]
    (Lang.list_t Lang.string_t)
    (fun p ->
      let enc, encoding = get_encoding p in
      let s = Lang.to_string (List.assoc "" p) in
      try Lang.list (List.map Lang.string (split ~encoding s))
      with _ ->
        Runtime_error.raise ~pos:(Lang.pos p)
          ~message:
            (Printf.sprintf "String cannot be split using encoding `\"%s\"`!"
               enc)
          "invalid")

let _ =
  Lang.add_builtin ~base:string "length" ~category:`String
    ~descr:
      "Return the string's length using the given encoding. Raises \
       `error.invalid` on errors."
    [encoding_option; ("", Lang.string_t, None, None)]
    Lang.int_t
    (fun p ->
      let enc, encoding = get_encoding p in
      let s = Lang.to_string (List.assoc "" p) in
      try Lang.int (List.length (split ~encoding s))
      with _ ->
        Runtime_error.raise ~pos:(Lang.pos p)
          ~message:
            (Printf.sprintf "String cannot be split using encoding `\"%s\"`!"
               enc)
          "invalid")

let _ =
  Lang.add_builtin ~base:string "nth" ~category:`String
    ~descr:
      "Retrieve a character in a string. Raises `error.not_found` if character \
       does not exist."
    ~examples:
      [
        {|
c = string.nth("abcde", 2)
print(c) # should print 99 which is the ascii code for "c"
|};
      ]
    [
      ("", Lang.string_t, None, Some "String to look into.");
      ("", Lang.int_t, None, Some "Index of the character.");
    ]
    Lang.int_t
    (fun p ->
      try
        let s = Lang.to_string (Lang.assoc "" 1 p) in
        let n = Lang.to_int (Lang.assoc "" 2 p) in
        Lang.int (int_of_char s.[n])
      with _ ->
        Runtime_error.raise ~pos:(Lang.pos p)
          ~message:"string.nth: character not found!" "not_found")

let _ =
  Lang.add_builtin ~base:string "char" ~category:`String
    ~descr:"Create a string with one character."
    [("", Lang.int_t, None, Some "Code of the character.")]
    Lang.string_t
    (fun p ->
      List.assoc "" p |> Lang.to_int |> Char.chr |> String.make 1 |> Lang.string)

let string_escape =
  Lang.add_builtin ~base:string "escape" ~category:`String
    ~descr:
      "Escape special characters in an string. By default, the string is \
       assumed to be `\"utf8\"` encoded and is escaped following JSON and \
       javascript specification."
    [
      ( "special_char",
        Lang.nullable_t
          (Lang.fun_t
             [(false, "encoding", Lang.string_t); (false, "", Lang.string_t)]
             Lang.bool_t),
        Some Lang.null,
        Some
          "Return `true` if the given character (passed as a string) should be \
           escaped. Defaults to control characters for `\"utf8\"` and control \
           characters and any character above `\\x7E` (non-printable \
           characters) for `\"ascii\"`." );
      ( "escape_char",
        Lang.nullable_t
          (Lang.fun_t
             [(false, "encoding", Lang.string_t); (false, "", Lang.string_t)]
             Lang.string_t),
        Some Lang.null,
        Some
          "Function used to escape a character. Defaults to `\\xxx` octal \
           notation for `\"ascii\"` and `\\uxxxx` hexadecimal notation for \
           `\"utf8\"`." );
      ( "encoding",
        Lang.nullable_t Lang.string_t,
        Some Lang.null,
        Some
          "One of: `\"ascii\"` or `\"utf8\"`. If `null`, `utf8` is tried first \
           and `ascii` is used as a fallback if this fails." );
      ("", Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let s = Lang.to_string (List.assoc "" p) in
      let encoding = List.assoc "encoding" p in
      let encoding : [ `Default | `Ascii | `Utf8 ] =
        match Lang.to_valued_option Lang.to_string encoding with
          | None -> `Default
          | Some "ascii" -> `Ascii
          | Some "utf8" -> `Utf8
          | Some _ ->
              raise
                (Error.Invalid_value
                   ( encoding,
                     "Encoding should be one of: \"ascii\" or \"utf8\"." ))
      in
      let exec encoding =
        let encoding_string =
          match encoding with `Utf8 -> "utf8" | `Ascii -> "ascii"
        in
        let special_char =
          match (Lang.to_option (List.assoc "special_char" p), encoding) with
            | Some f, _ ->
                fun s ofs len ->
                  Lang.to_bool
                    (Lang.apply f
                       [
                         ("encoding", Lang.string encoding_string);
                         ("", Lang.string (String.sub s ofs len));
                       ])
            | None, `Ascii -> Lang_string.ascii_special_char
            | None, `Utf8 -> Lang_string.utf8_special_char
        in
        let escape_char =
          match (Lang.to_option (List.assoc "escape_char" p), encoding) with
            | Some f, _ ->
                fun s ofs len ->
                  Lang.to_string
                    (Lang.apply f
                       [
                         ("encoding", Lang.string encoding_string);
                         ("", Lang.string (String.sub s ofs len));
                       ])
            | None, `Ascii -> Lang_string.escape_hex_char
            | None, `Utf8 -> Lang_string.escape_utf8_char ~strict:false
        in
        let next =
          match encoding with
            | `Ascii -> Lang_string.ascii_next
            | `Utf8 -> Lang_string.utf8_next
        in
        try
          Lang.string
            (Lang_string.escape_string
               (Lang_string.escape ~special_char ~escape_char ~next)
               s)
        with _ ->
          let bt = Printexc.get_raw_backtrace () in
          Runtime_error.raise ~bt ~pos:(Lang.pos p)
            ~message:
              (Printf.sprintf "Error while escaping %s string.%s"
                 (match encoding with `Utf8 -> "utf8" | `Ascii -> "ascii")
                 (if encoding <> `Ascii then
                    " If you are not sure about the string's encoding, you \
                     should use `\"ascii\"` as this encoding never fails."
                  else ""))
            "string"
      in
      match encoding with
        | `Default -> ( try exec `Utf8 with _ -> exec `Ascii)
        | (`Ascii | `Utf8) as encoding -> exec encoding)

let _ =
  Lang.add_builtin ~base:string_escape "all"
    ~descr:
      "Escape each character in the given string using a specific escape \
       sequence."
    ~category:`String
    [
      ( "format",
        Lang.string_t,
        Some (Lang.string "utf8"),
        Some "Escape format. One of: `\"octal\"`, `\"hex\"` or `\"utf8\"`." );
      ("", Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let format = List.assoc "format" p in
      let escape_char, next =
        match Lang.to_string format with
          | "octal" -> (Lang_string.escape_octal_char, Lang_string.ascii_next)
          | "hex" -> (Lang_string.escape_hex_char, Lang_string.ascii_next)
          | "utf8" ->
              (Lang_string.escape_utf8_char ~strict:false, Lang_string.utf8_next)
          | _ ->
              raise
                (Error.Invalid_value
                   ( format,
                     "Format should be one of: `\"octal\"`, `\"hex\"` or \
                      `\"utf8\"`." ))
      in
      let s = Lang.to_string (List.assoc "" p) in
      Lang.string
        (Lang_string.escape_string
           (Lang_string.escape
              ~special_char:(fun _ _ _ -> true)
              ~escape_char ~next)
           s))

let _ =
  Lang.add_builtin ~base:string_escape "special_char"
    ~descr:
      "Default function to detect characters to escape. See `string.escape` \
       for more details."
    ~category:`String
    [
      ( "encoding",
        Lang.string_t,
        Some (Lang.string "utf8"),
        Some "One of: `\"ascii\"` or `\"utf8\"`." );
      ("", Lang.string_t, None, None);
    ]
    Lang.bool_t
    (fun p ->
      let s = Lang.to_string (List.assoc "" p) in
      let len = String.length s in
      let encoding = List.assoc "encoding" p in
      match Lang.to_string encoding with
        | "ascii" -> Lang.bool (Lang_string.ascii_special_char s 0 len)
        | "utf8" -> Lang.bool (Lang_string.utf8_special_char s 0 len)
        | _ ->
            raise
              (Error.Invalid_value
                 (encoding, "Encoding should be one of: \"ascii\" or \"utf8\".")))

let _ =
  Lang.add_builtin ~base:string "unescape"
    ~descr:"This function is the inverse of `string.escape`." ~category:`String
    [("", Lang.string_t, None, None)]
    Lang.string_t
    (fun p ->
      let s = Lang.to_string (List.assoc "" p) in
      Lang.string (Lang_string.unescape_string s))

let _ =
  Lang.add_builtin ~base:string "sub" ~category:`String
    ~descr:
      "Get a substring of a string. Returns \"\" if no such substring exists."
    [
      ("", Lang.string_t, None, None);
      ( "start",
        Lang.int_t,
        None,
        Some
          "Return a sub string starting at this position. First position is 0."
      );
      encoding_option;
      ( "length",
        Lang.int_t,
        None,
        Some "Return a sub string of `length` characters." );
    ]
    Lang.string_t
    (fun p ->
      let start = Lang.to_int (List.assoc "start" p) in
      let len = Lang.to_int (List.assoc "length" p) in
      let _, encoding = get_encoding p in
      let string = Lang.to_string (List.assoc "" p) in
      let s =
        match encoding with
          | `Ascii -> (
              try String.sub string start len with Invalid_argument _ -> "")
          | `Utf8 -> (
              try
                let chars = split ~encoding string in
                if List.length chars < len + start then ""
                else
                  String.concat ""
                    (List.filteri
                       (fun pos _ -> start <= pos && pos < start + len)
                       chars)
              with _ -> "")
      in
      Lang.string s)

let _ =
  Lang.add_builtin ~base:string "index" ~category:`String
    ~descr:
      "Index where a substring occurs in a string. The function returns `-1` \
       if the substring is not present"
    [
      ("substring", Lang.string_t, None, Some "Substring to look for.");
      ("", Lang.string_t, None, Some "String in which to look.");
    ]
    Lang.int_t
    (fun p ->
      let t = List.assoc "substring" p |> Lang.to_string in
      let s = List.assoc "" p |> Lang.to_string in
      let ans =
        let m = String.length t in
        let n = String.length s in
        let ans = ref (-1) in
        try
          for i = 0 to n - m do
            if String.sub s i m = t then (
              ans := i;
              raise Exit)
          done;
          -1
        with Exit -> !ans
      in
      Lang.int ans)

let _ =
  Lang.add_builtin ~base:string "case" ~category:`String
    ~descr:"Convert a string to lower or upper case."
    [
      ( "lower",
        Lang.bool_t,
        Some (Lang.bool true),
        Some "Convert to lower case if true and uppercase otherwise." );
      ("", Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let lower = Lang.to_bool (List.assoc "lower" p) in
      let string = Lang.to_string (List.assoc "" p) in
      Lang.string
        (if lower then String.lowercase_ascii string
         else String.uppercase_ascii string))

let _ =
  Lang.add_builtin ~base:string "trim" ~category:`String
    ~descr:"Return a string without leading and trailing whitespace."
    [("", Lang.string_t, None, None)]
    Lang.string_t
    (fun p -> Lang.string (String.trim (Lang.to_string (List.assoc "" p))))

let _ =
  Lang.add_builtin ~base:string "capitalize" ~category:`String
    ~descr:
      "Return a string with the first character set to upper case \
       (capitalize), or to lower case (uncapitalize)."
    [
      ( "capitalize",
        Lang.bool_t,
        Some (Lang.bool true),
        Some "Capitalize if true, uncapitalize otherwise" );
      ( "space_sensitive",
        Lang.bool_t,
        Some (Lang.bool true),
        Some "Capitalize each space separated sub-string." );
      ("", Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let cap = Lang.to_bool (List.assoc "capitalize" p) in
      let space_sensitive = Lang.to_bool (List.assoc "space_sensitive" p) in
      let string = Lang.to_string (List.assoc "" p) in
      let f s =
        if cap then String.capitalize_ascii s else String.uncapitalize_ascii s
      in
      Lang.string
        (if space_sensitive then (
           let l = String.split_on_char ' ' string in
           let l = List.map f l in
           String.concat " " l)
         else f string))

let _ =
  Lang.add_builtin ~base:string "hex_of_int" ~category:`String
    ~descr:"Hexadecimal representation of an integer."
    [
      ( "pad",
        Lang.int_t,
        Some (Lang.int 0),
        Some
          "Minimum length in digits (pad on the left with zeros in order to \
           reach it)." );
      ("", Lang.int_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let pad = Lang.to_int (List.assoc "pad" p) in
      let n = Lang.to_int (List.assoc "" p) in
      let s = Printf.sprintf "%x" n in
      let s =
        let len = String.length s in
        if len < pad then String.make (pad - len) '0' ^ s else s
      in
      Lang.string s)

(** Data conversions. *)

let () =
  (* Register as [name] the function which composes [in_value],[func] and
   * [out_value], and returns [default] in exceptional cases -- which MUST not
   * occur when default is not supplied. *)
  let register_tt doc name category func ~needs_default in_type in_value
      out_value out_type =
    let raise_doc =
      if needs_default then
        [%string
          {| Raises `error.failure("%{doc}")` if conversion fails and default is `null`|}]
      else ""
    in
    ignore
      (Lang.add_builtin name ~category
         ~descr:[%string {|Convert %{doc}.%{raise_doc}|}]
         ([("", in_type, None, None)]
         @
         if needs_default then
           [("default", Lang.nullable_t out_type, Some Lang.null, None)]
         else [])
         out_type
         (fun p ->
           try out_value (func (in_value (List.assoc "" p)))
           with _ -> (
             try Option.get (Lang.to_option (List.assoc "default" p))
             with _ ->
               Runtime_error.raise ~pos:(Lang.pos p) ~message:name "failure")))
  in
  let register_tts name func out_value out_type =
    register_tt ~needs_default:true ("a string to a " ^ name)
      (name ^ "_of_string") `String func Lang.string_t Lang.to_string out_value
      out_type
  in
  let register_tti name func out_value out_type =
    register_tt ~needs_default:false ("an int to a " ^ name) (name ^ "_of_int")
      `Math func Lang.int_t Lang.to_int out_value out_type
  in
  let register_ttf name func out_value out_type =
    register_tt ~needs_default:false ("a float to a " ^ name)
      (name ^ "_of_float") `Math func Lang.float_t Lang.to_float out_value
      out_type
  in
  register_tts "int" int_of_string (fun v -> Lang.int v) Lang.int_t;
  register_tts "float" float_of_string (fun v -> Lang.float v) Lang.float_t;
  register_tts "bool" bool_of_string (fun v -> Lang.bool v) Lang.bool_t;
  register_tti "float" float_of_int (fun v -> Lang.float v) Lang.float_t;
  register_tti "bool" (fun v -> v = 1) (fun v -> Lang.bool v) Lang.bool_t;
  register_ttf "int" int_of_float (fun v -> Lang.int v) Lang.int_t;
  register_ttf "bool" (fun v -> v = 1.) (fun v -> Lang.bool v) Lang.bool_t

let _ =
  Lang.add_builtin ~base:string "float" ~category:`String
    ~descr:"String representation of a float."
    [
      ( "decimal_places",
        Lang.nullable_t Lang.int_t,
        Some Lang.null,
        Some "Number of decimal places." );
      ("", Lang.float_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let dp =
        List.assoc "decimal_places" p
        |> Lang.to_option |> Option.map Lang.to_int
      in
      let x = List.assoc "" p |> Lang.to_float in
      let s =
        match dp with
          | Some d -> Printf.sprintf "%.*f" d x
          | None -> Utils.string_of_float x
      in
      Lang.string s)

let _ =
  Lang.add_builtin ~base:string "make" ~category:`String
    ~descr:"Create a string of a given length using the given character."
    [
      ( "char_code",
        Lang.int_t,
        Some (Lang.int (Char.code ' ')),
        Some "Character code." );
      ("", Lang.int_t, None, Some "String length.");
    ]
    Lang.string_t
    (fun p ->
      let n = Lang.to_int (List.assoc "" p) in
      if n < 0 then
        Runtime_error.raise ~pos:(Lang.pos p) ~message:"Invalid string length!"
          "invalid";
      let c =
        try Char.chr (Lang.to_int (List.assoc "char_code" p))
        with _ ->
          Runtime_error.raise ~pos:(Lang.pos p)
            ~message:"Invalid character code!" "invalid"
      in
      Lang.string (String.make n c))

let _ =
  Lang.add_builtin ~base:string "id" ~category:`String
    ~descr:"Generate an identifier with given operator name."
    [("", Lang.string_t, None, Some "Operator name.")]
    Lang.string_t
    (fun p ->
      let name = List.assoc "" p |> Lang.to_string in
      Lang.string (Lang_string.generate_id name))

let string_base64 = Lang.add_module ~base:string "base64"

let _ =
  Lang.add_builtin ~base:string_base64 "decode" ~category:`String
    ~descr:"Decode a Base64 encoded string."
    [("", Lang.string_t, None, None)]
    Lang.string_t
    (fun p ->
      let string = Lang.to_string (List.assoc "" p) in
      try Lang.string (Lang_string.decode64 string)
      with _ ->
        Runtime_error.raise ~pos:(Lang.pos p) ~message:"Invalid base64 string!"
          "invalid")

let _ =
  Lang.add_builtin ~base:string_base64 "encode" ~category:`String
    ~descr:"Encode a string in Base64."
    [("", Lang.string_t, None, None)]
    Lang.string_t
    (fun p ->
      let string = Lang.to_string (List.assoc "" p) in
      Lang.string (Lang_string.encode64 string))

let url = Modules.url

let _ =
  Lang.add_builtin ~base:url "decode" ~category:`String
    ~descr:"Decode an encoded url (e.g. \"%20\" becomes \" \")."
    [
      ("plus", Lang.bool_t, Some (Lang.bool true), None);
      ("", Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let plus = Lang.to_bool (List.assoc "plus" p) in
      let string = Lang.to_string (List.assoc "" p) in
      Lang.string (Lang_string.url_decode ~plus string))

let _ =
  Lang.add_builtin ~base:url "encode" ~category:`String
    ~descr:"Encode an url (e.g. \" \" becomes \"%20\")."
    [
      ("plus", Lang.bool_t, Some (Lang.bool true), None);
      ("", Lang.string_t, None, None);
    ]
    Lang.string_t
    (fun p ->
      let plus = Lang.to_bool (List.assoc "plus" p) in
      let string = Lang.to_string (List.assoc "" p) in
      Lang.string (Lang_string.url_encode ~plus string))
OCaml

Innovation. Community. Security.