Module Fmlib_parse.Indent

The allowed indentations: Helper module for indentation sensitive parsing.

type expectation =
| Indent of int

Indent n An indentation of at least n columns is expected.

| Align of int

Align n Start at colmun n is expected.

| Align_between of int * int

Align_between a b Start between the columns a and b is expected.

The expected indentiation.

type violation = expectation

Use expectation!

val group : ('a * expectation option) list -> (expectation option * 'a list) list

group lst Group the list of expectations.

Failed expectations with the same indentation expectation (or not indentation expectation) are grouped into one list. The sequence is not changed.

type t

Allowed indentations

val expectation : t -> expectation option

expectation ind The expected indentation or alignment. Returns None if all positions are allowed.

val initial : t

Initially all indentations 0,1,... are allowed and no alignment is required.

val check_position : int -> t -> expectation option

check_position col ind Return a violated expectation, if pos is not an allowed indentation position. Otherwise return None.

val token : int -> t -> t

token pos ind Accept a token at column pos.

Preconditions: is_position_allowed pos ind.

val align : t -> t

align ind Set the alignment flag.

The next token sets the indentation set to {pos} where pos is the column of the token and clears the aligment flag.

val left_align : t -> t

left_align ind Set the alignment flag and the indentation set to {pos} where pos is the lower bound of the current set of indentation positions.

val end_align : t -> t -> t

end_align ind0 ind End the aligned sequence i.e. handle the corner case that the aligned sequence is empty.

val start_indent : int -> t -> t

start_indent i ind Start an indented grammar construct indented by at least i relative to its parent.

If the aligmnent flag is set, indentation is ignored.

Precondition: 0 <= incr

val end_indent : int -> t -> t -> t

end_indent i ind0 ind End the current indentation which has been started with and indentation of i columns relative to ind0.