package reparse-lwt

p >>= f returns a new parser b where,

• a is the parsed value of p
• b is f a Also known as bind operation.

Examples

module P = Reparse.String
open P;;

let f a = P.pure (Char.code a) in
let p = P.char 'h' in
let p = p >>= f in
let v = P.parse_string p "hello" in
v = 104

p >>| f returns a new parser encapsulating value b where,

• a is the parsed value of p.
• b is f a. Also known as map operation.

Examples

module P = Reparse.String
open P;;

let f a = Char.code a in
let p = P.char 'h' in
let p = p >>| f in
let v = P.parse_string p "hello" in
v = 104

pf <*> q returns a new parser encapsulating value b where

• pf and q are evaluated sequentially in order as given.
• f is the parsed value of pf
• a is the parsed value of q
• b is f a Also known as Applicative operation.

Examples

module P = Reparse
open P;;

let f a = a + 2 in
let pf = P.pure f in
let q = P.pure 2 in
let p = pf <*> q in
let v = P.parse_string p "hello" in
v = 4

f <$> p is return f <*> p.

v <$ p replaces the parse value of p with v.

Examples

module P = Reparse.String
open P;;

let v = "hello" in
let p = P.char 'h' in
let p = v <$ p in
let v2 = P.parse_string p "hello" in
v2 = "hello"

p $> v is inverse of v <$ p.

p *> q returns a parser encapsulating value a where,

• p, q are evaluated sequentially in order as given.
• a is parsed value of q.
• The parsed value of p is discarded. Also known as discard left.

Examples

module P = Reparse.String
open P;;

let p = P.string "world" in
let q = P.pure "hello" in
let p = p *> q in
let v = P.parse_string p "world" in
v = "hello"

p <* q returns a parser encapsulating value a where,

• p, q are evaluated sequentially in order as given.
• a is parsed value of p.
• The parsed value of q is discarded. Also know as discard_right.

Examples

module P = Reparse.String
open P;;

let p = P.string "world" in
let q = P.pure "hello" in
let p = p <* q in
let v = P.parse_string p "world" in
v = "world"

p <|> q returns a parser encapsulating value a where,

• p,q are evaluated sequentially in order as given.
• a is the parsed value of p if p is successful
• a is the parsed value of q if p is a failure and q is a success.
• If both - p and q - fails, then the parser fails.

Examples

p fails and q succeeds, therefore we return q's parsed value 'w'

module P = Reparse.String
open P;;

let p = P.char 'h' in
let q = P.char 'w' in
let p = p <|> q in
let v = P.parse_string p "world" in
v = 'w'

p succeeds therefore we return its parsed value 'h'

let p = P.char 'h' in
let q = P.char 'w' in
let p = p <|> q in
let v = P.parse_string p "hello" in
v = 'h'

The parser fails if both p and q fails.

let p = P.char 'h' in
let q = P.char 'w' in
let p = p <|> q in
let v =
  try
    let _ = P.parse_string p "" in
    false
  with _ -> true
in
v = true

let* is a let syntax binding for Reparse.Infix.((>>=))

Examples

module P = Reparse.String
open P;;

let p =
  let* a = P.pure 5 in
  let total = a + 5 in
  P.pure total
in
let v = P.parse_string p "" in
v = 10

let* is a let syntax binding for Reparse.((>|=))

Examples

module P = Reparse.String
open P;;

let p =
  let+ a = P.pure 5 in
  let total = a + 5 in
  total
in
let v = P.parse_string p "" in
v = 10

p <?> err_msg parses p to value a and returns a new parser encapsulating a. If p is a failure, then it fails with error message err_msg. Often used as a last choice in <|>, e.g. a <|> b <|> c <?> "expected a b c".

Examples

module P = Reparse.String
open P;;

let p = P.char 'h' <|> P.char 'w' in
let err_msg = "[error]" in
let p = p <?> err_msg in
let v =
  try
    let _ = P.parse_string p "" in
    false
  with
  | P.Parser
      {offset= 0; line_number= 0; column_number= 0; msg= "[error]"} ->
      true
  | _ -> false
in
v = true