# package dolmen

Signature required by terms for typing first-order polymorphic terms.

`module Var : sig ... end`

A module for variables that occur in terms.

`module Const : sig ... end`

A module for constant symbols that occur in terms.

`module Cstr : sig ... end`

A module for Algebraic datatype constructors.

`module Field : sig ... end`

```
val define_adt :
ty_const ->
ty_var list ->
(path * (ty * path option) list) list ->
(Cstr.t * (ty * Const.t option) list) list
```

`define_aft t vars cstrs`

defines the type constant `t`

, parametrised over the type variables `ty_vars`

as defining an algebraic datatypes with constructors `cstrs`

. `cstrs`

is a list where each elements of the form `(name, l)`

defines a new constructor for the algebraic datatype, with the given name. The list `l`

defines the arguments to said constructor, each element of the list giving the type `ty`

of the argument expected by the constructor (which may contain any of the type variables in `vars`

), as well as an optional destructor name. If the construcotr name is `Some s`

, then the ADT definition also defines a function that acts as destructor for that particular field. This polymorphic function is expected to takes as arguments as many types as there are variables in `vars`

, an element of the algebraic datatype being defined, and returns a value for the given field. For instance, consider the following definition for polymorphic lists: ```
define_adt list [ty_var_a] [
"nil", [];
"const", [
(Ty.of_var ty_var_a , Some "hd");
(ty_list_a , Some "tl");
];
]
```

This definition defines the usual type of polymorphic linked lists, as well as two destructors "hd" and "tl". "hd" would have type `forall alpha. alpha list -> a`

, and be the partial function returning the head of the list.

Define a (previously abstract) type to be a record type, with the given fields.

Exception raised in case of typing error during term construction. `Wrong_type (t, ty)`

should be raised by term constructor functions when some term `t`

is expected to have type `ty`

, but does not have that type.

Raised when some constructor was expected to belong to some type but does not belong to the given type.

Exception raised in case of typing error during term construction. This should be raised when the returned field was expected to be a field for the returned record type constant, but it was of another record type.

`exception Field_repeated of Field.t`

Field repeated in a record expression.

`exception Field_missing of Field.t`

Field missing in a record expression.

`exception Pattern_expected of t`

Raised when trying to create a pattern matching, but a non-pattern term was provided where a pattern was expected.

Raise when creating a pattern matching but an empty list of branches was provided

`exception Partial_pattern_match of t list`

Raised when a partial pattern matching was created. A list of terms not covered by the patterns is provided.

`exception Over_application of t list`

Raised when an application was provided too many term arguments. The extraneous arguments are returned by the exception.

Raised when a polymorphic application does not have an adequate number of arguments.

Given a constructor `c`

and a term `t`

, returns a terms that evaluates to `true`

iff `t`

has `c`

as head constructor.

Universally quantify the given formula over the type and terms variables.

Existencially quantify the given formula over the type and terms variables.

Bind a variable to an expressions. This function is called when typing a let-binding, before the body of the let-binding is typed. The returned expressions is used to replace the variable everywhere in the body of the let-binding being typed.

`pattern_match scrutinee branches`

creates a pattern match expression on the scrutinee with the given branches, each of the form `(pattern, body)`