`Generic.Make`

`Token.t`

Token type`State.t`

Type of the user state`Expect.t`

Type of syntax messages which are generated, when something has been expected but not found.`Semantic.t`

Type of semantic error messages. Triggered by`fail error`

.`Final.t`

Type of the returned object, when parsing has finished.

`module Token : Fmlib_std.Interfaces.ANY`

`module State : Fmlib_std.Interfaces.ANY`

`module Expect : Fmlib_std.Interfaces.ANY`

`module Semantic : Fmlib_std.Interfaces.ANY`

`module Final : Fmlib_std.Interfaces.ANY`

`module Parser : sig ... end`

The final parser.

`type state = State.t`

`type expect = Expect.t`

`type semantic = Semantic.t`

`p >>= f`

Parse first the input according to the combinator `p`

. In case of success, feed the returned value of `p`

into the function `f`

to get the combinator to parse next.

`let* x = p in f x`

is equivalent to `p >>= f`

The `let*`

combinator let us express parsing sequences conveniently. Example:

```
let* x = p in (* parse [p], result [x] in case of success. *)
let* y = q x in (* parse [q x], result [y] ... *)
let* z = r x y in (* ... *)
...
return f x y z ...
```

The wildcard `let* _ = ...`

can be used to ignore results of intermediate parsing steps.

`map f p`

Try combinator `p`

. In case of success, map the returned value `x`

to ```
f
x
```

. In case of failure, do nothing.

`map f p`

is equivalent to `let* x = p in return (f x)`

.

`map_and_update f p`

Try combinator `p`

. In case of success, map the returned state `state`

and value `a`

to `f state a`

. In case of failure, do nothing.

`val succeed : 'a -> 'a t`

`succeed a`

Succeed immediately without consuming token. Return object `a`

as result.

`val return : 'a -> 'a t`

`return a`

is equivalent to `succeed a`

.

`unexpected expect`

triggers a syntax error signalling the expectation `expect`

.

`val clear_last_expectation : 'a -> 'a t`

`clear_last_expectation p`

Clear last failed expectation.

This is useful e.g. after stripping whitespace. Since stripping whitespace means `skip_one_or_more ws`

or `skip_zero_or_more ws`

, after skipping whitespace the parser can still expect more whitespace. Therefore there is a failed expectation *whitespace* on the stack. However you rarely want this expectation to be reported.

`p </> q`

Try first combinator `p`

. In case of success or failure with consumed token, `p </> q`

is equivalent to `p`

.

If `p`

fails without consuming token, then `p </> q`

is equivalent to `q`

.

`choices p [q r t ...]`

is equivalent to `p </> q </> r </> t </> ...`

.

`p <?> expect`

Try combinator `p`

. In case of success or failure with consumed token, `p <?> expect`

is equivalent to `p`

.

If `p`

fails without consuming token, then the failed expectations are replaced with the failed expectation `expect`

.

Usually `p`

is a combinator implementing a choice between various alternatives of a grammar construct. The `<?>`

combinator allows to replace the set of failed grammar alternatives with a higher abstraction of the failed expectation. E.g. instead of getting the failed expectations `identifier`

, `'('`

, `-`

, ... we can get the failed expectation `expression`

.

`no_expectations p`

Parse the combinator `p`

.

`p`

fails:`no_expectations p`

fails with the same error.

`p`

succeeds without consuming tokens:`no_expectations p`

succeeds without any added expectations.

`p`

succeeds and consumes some token:`no_expectations p`

succeeds without any expectations.

Many combinators can succeed with expectations. E.g. the combinator `optional p`

expects a `p`

and succeeds if it does not encounter a construct described by `p`

. All repetitive combinators like `one_or_more`

try to consume as many items as possible. At the end they are still expecting an item.

This combinator allows to clear such unneeded expectations. It is particularly useful when removing whitespace. The expectation of whitespace is not a meaningful error message to the user.

`get_and_update f`

Get the current user state and then update the user state. The returned value is the old state.

`state_around before p after`

If `s0`

is the initial state, then execute `p`

with the start state `before s0`

and set the update the final state `s1`

by `after s0 a s1`

where `a`

is the returned value in case of success and `s1`

is the final state after executing `p`

.

`optional p`

Try combinator `p`

.

- Success: Return
`Some a`

where`a`

is the returned value. - Failure without consuming token: Return
`None`

- Failure with consuming token: Remain in the error state.

`zero_or_more_fold_left start f p`

Try the combinator `p`

as often as possible. Accumulate the results to the start value `start`

using the folding function `f`

.

`one_or_more_fold_left first f p`

Try the combinator `p`

at least once and then as often as possible. Put the first value returned by `p`

into the function `first`

returning a result and accumulate the subsequent values as often as possible and accumulate the results to the start value returned by `first`

using the folding function `f`

.

`zero_or_more p`

Parse zero or more occurrences of `p`

and return the collected result in a list.

`zero_or_more p`

Parse one or more occurrences of `p`

and return the collected results as a pair of the first value and a list of the remaining values.

`skip_zero_or_more p`

Parse zero or more occurrences of `p`

, ignore the result and return the number of occurrences.

`skip_one_or_more p`

Parse one or more occurrences of `p`

, ignore the result and return the number of occurrences.

```
val one_or_more_separated :
('item -> 'r t) ->
('r -> 'sep -> 'item -> 'r t) ->
'item t ->
'sep t ->
'r t
```

`one_or_more_separated first next p sep`

Parse one or more occurrences of `p`

separated by `sep`

. Use `first`

to convert the first occurrence of `p`

into the result and use `next`

to accumulate the results.

```
val parenthesized :
('lpar -> 'a -> 'rpar -> 'b t) ->
'lpar t ->
(unit -> 'a t) ->
('lpar -> 'rpar t) ->
'b t
```

`parenthesized make lpar p rpar`

Parse an expression recognized by the combinator `p`

enclosed within parentheses. `lpar`

recognizes the left parenthesis and `rpar`

recognizes the right parenthesis. The value returned by `lpar`

is given to `rpar`

. With that mechanism it is possible to recognize matching parentheses of different kinds.

After successful parsing the function `make`

is called with the final value (and the parentheses).

The combinator `p`

is entered as a thunk in order to be able to call it recursively. In the combinator `parenthesized`

the combinator `p`

is called only guardedly. Therefore the combinator `p`

can contain nested parenthesized expressions.

Precondition: The combinator `lpar`

has to consume at least one token in case of success.

```
val operator_expression :
'exp t ->
'op t option ->
'op t ->
('op -> 'op -> bool t) ->
('op -> 'exp -> 'exp t) ->
('exp -> 'op -> 'exp -> 'exp t) ->
'exp t
```

```
operator_expression
primary (* Parse a primary expression *)
unary_operator (* Parse a unary operator *)
binary_operator (* Parse a binary operator *)
is_left (* Is the left operator binding stronger? *)
make_unary (* Make a unary expression from the operator and
its operand *)
make_binary (* Make a binary expression from the operator
and its operands *)
```

Parse an operator expression by using the following combinators:

`is_left o1 o2`

decides, if the operator`o1`

on the left has more binding power than the operator`o2`

. I.e. if the unary operator`u`

has more binding power than the binary operator`o`

, then`u a o b`

is parsed as`(u a) o b`

. If the binary operator`o1`

has more binding power than the binary operator`o2`

, then`a o1 b o2 b`

is parsed as`(a o1 b) o2 c`

.

`make_unary u a`

makes the unary expression`(u a)`

.

`make_binary a o b`

makes the binary expression`(a o b)`

.

`primary`

parses a primary expression.

`unary_operator`

parses a unary operator.

`binary_operator`

parses a binary operator.

Precondition: `primary`

, `unary_operator`

and `binary_operator`

have to consume at least one token in case of success. Otherwise infinite recursion can happen.

`backtrack p expect`

Try the combinator `p`

. In case of failure with consuming token, push the consumed token back to the lookahead and let it fail without consuming token. Use `expect`

to record the failed expectation.

Backtracking reduces the performance, because the token pushed back to the lookahead have to be parsed again. Try to avoid backtracking whenever possible.

`followed_by p expect`

Parses `p`

and backtracks (i.e. all tokens of `p`

will be pushed back to the lookahead). In case `p`

succeeds, the `followed_by`

parser succeeds without consuming token. Otherwise it fails without consuming tokens.

`not_followed_by p expect`

Parses `p`

and backtracks (i.e. all tokens of `p`

will be pushed back to the lookahead). In case `p`

succeeds, the `not_followed_by`

parser fails without consuming token. Otherwise it succeeds without consuming tokens.

`followed_by`

and `not_followed_by`

can be used to peek into the token stream without consuming token.

`step f`

Elementary parsing step.

The function `f`

is called with two arguments:

- The current state
- The next lookahead token (or none, if the end of the token stream has been reached).

`f`

must return either an object of type `'a`

and a new state if it accepts the token, or a failed expectation if it rejects the token.

`expect_end error a`

Expect the end of input.

In case of success return `a`

. In case of failure (i.e. not yet at the end of input) then compute via `error`

the syntax error from the state.

WARNING: This combinator only makes sense if you generate your parser with `make_parser`

. If you generate your parser with `make`

then the end of input is automatically expected after the toplevel construct.

`make state p e`

Makes a parser.

`state`

Initial state`p`

Combinator which returns in case of success an object of type`Final.t`

`e`

Error function. Generates an expectation from the state. The function is used if an other token arrives at the expected end of input.

The generated parser expects a token stream which can be successfully parsed by the combinator `p`

. It can succeed only if an end token is pushed to the parser.