is_valid s is true iff only for all indices i of s, s.[i] is an ASCII character, i.e. a byte in the range [0x00;0x1F].

uppercase s is s with ASCII characters 'a' to 'z' mapped to 'A' to 'Z'.

lowercase s is s with ASCII characters 'A' to 'Z' mapped to 'a' to 'z'.

capitalize s is like Ascii.uppercase but performs the map only on s.[0].

uncapitalize s is like Ascii.lowercase but performs the map only on s.[0].

to_hex s is the sequence of bytes of s as ASCII lowercase hexadecimal digits.

of_hex' h parses a sequence of ASCII (lower or upper cased) hexadecimal digits from h into its corresponding byte sequence. Error n is returned either with n an index in the string which is not a hexadecimal digit or the length of h if it there is a missing digit at the end.

of_hex is of_hex' but errors with an english error message.

escape s escapes bytes of s to a representation that uses only ASCII printable characters. More precisely:

• [0x20;0x5B] and [0x5D;0x7E] are left unchanged. These are the printable ASCII bytes, except '\\' (0x5C).
• [0x00;0x1F], 0x5C and [0x7F;0xFF] are escaped by an hexadecimal "\xHH" escape with H a capital hexadecimal number. These bytes are the ASCII control characters, the non ASCII bytes and '\\' (0x5C).

Use unescape to unescape. The invariant unescape (escape s) = Ok s holds.

unescape s unescapes from s the escapes performed by escape. More precisely:

• "\xHH" with H a lower or upper case hexadecimal number is unescaped to the corresponding byte value.

Any other escape following a '\\' not defined above makes the function return Error i with i the index of the error in the string.

ocaml_string_escape s escapes the bytes of s to a representation that uses only ASCII printable characters and according to OCaml's conventions for string literals. More precisely:

• '\b' (0x08) is escaped to "\\b" (0x5C,0x62).
• '\t' (0x09) is escaped to "\\t" (0x5C,0x74).
• '\n' (0x0A) is escaped to "\\n" (0x5C,0x6E).
• '\r' (0x0D) is escaped to "\\r" (0x5C,0x72).
• '\"' (0x22) is escaped to "\\\"" (0x5C,0x22).
• '\\' (0x5C) is escaped to "\\\\" (0x5C,0x5C).
• 0x20, 0x21, [0x23;0x5B] and [0x5D;0x7E] are left unchanged. These are the printable ASCII bytes, except '\"' (0x22) and '\\' (0x5C).
• Remaining bytes are escaped by an hexadecimal "\xHH" escape with H an uppercase hexadecimal number. These bytes are the ASCII control characters not mentioned above and non ASCII bytes.

Use ocaml_unescape to unescape. The invariant ocaml_unescape (ocaml_string_escape s) = Ok s holds.

ocaml_unescape s unescapes from s the escape sequences afforded by OCaml string and char literals. More precisely:

• "\\b" (0x5C,0x62) is unescaped to '\b' (0x08).
• "\\t" (0x5C,0x74) is unescaped to '\t' (0x09).
• "\\n" (0x5C,0x6E) is unescaped to '\n' (0x0A).
• "\\r" (0x5C,0x72) is unescaped to '\r' (0x0D).
• "\\ " (0x5C,0x20) is unescaped to ' ' (0x20).
• "\\\"" (0x5C,0x22) is unescaped to '\"' (0x22).
• "\\'" (0x5C,0x27) is unescaped to '\'' (0x27).
• "\\\\" (0x5C,0x5C) is unescaped to '\\' (0x5C).
• "\xHH" with H a lower or upper case hexadecimal number is unescaped to the corresponding byte value.
• "\\DDD" with D a decimal number such that DDD is unescaped to the corresponding byte value.
• "\\oOOO" with O an octal number is unescaped to the corresponding byte value.

Any other escape following a '\\' not defined above makes the function return Error i with i the location of the error in the string.