User:Zzo38/Proposal for more-notation: Difference between revisions

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A more-declaration is a module-level declaration of this syntax:
A more-declaration is a module-level declaration of this syntax:
* ''['' ''numeric_literal'' ''|'' <tt>(</tt>''enumeration_constructor''<tt>)</tt> '']'' ''more_name'' ''{parameters}'' <tt>=</tt> ''contents'' ''{'' <tt>|</tt> ''contents'' ''}'' <tt>;</tt>
* ''['' ''numeric_literal'' ''|'' <tt>(</tt>''enumeration_constructor''<tt>)</tt> '']'' ''more_name'' ''{parameters}'' <tt>=</tt> ''contents'' ''{'' <tt>|</tt> ''contents'' ''}'' <tt>;</tt>
* ''numeric_literal'': It should be a natural number. Omitted is the same as zero.
* ''enumeration_constructor'': A constructor of the enumeration that was specified in the more-notation. If an enumeration is specified, the enumeration constructor is required here.
* ''parameters'': Lowercased names which will be scoped locally to this declaration. The number of parameters must match the number of parameters specified in the more-notation.
* ''contents'': The contents depends on where the more-notation is.


==Semantics==
==Semantics==
In the place where the more-notation is, all contents of more-declarations of that name will be reordered and corrected before being placed in place of the more-notation.
Automatic reordering is overridden by the enumeration constructors or numeric literals in front of more-declarations.


==Uses==
==Uses==
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===Datatype declarations===
===Datatype declarations===
A constructor definition in a data declaration is allowed to be replaced by a more-notation. Semantics of more-declarations becomes as follows:
* Duplicate constructors are removed.
* Duplicate constructors that do not match are errors.
* Multiple constructors in a single more-declaration are guaranteed to keep the order given.
Example:
data T = Zero | more T deriving (Eq);
T = Two | Three | Four;
T = One | Two;
becomes
data T = Zero | One | Two | Three | Four deriving (Eq);


===Fields in record syntax===
===Fields in record syntax===
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===Manipulation in splices===
===Manipulation in splices===
===Types and constructors===

Revision as of 20:47, 27 August 2011

This document is proposal for more-notation in Haskell.

Syntax

Anywhere that a more-notation is allowed (see Uses), you can use the syntax:

  • more [(name_of_enumeration)] more_name {parameters}
  • name_of_enumeration: A name of any type which is an enumeration. It can be another one using more-notation, but it must be able to fully determine it before this more-notation can be fully determined.
  • more_name: A capitalized name. It uses the same namespace as constructors, so you are not allowed to have a constructor of the same name (although it is OK to have types of the that name).
  • parameters: Optional lowercased names. These names are in local scope, and may already exist in this scope, although they do not have to.

A more-declaration is a module-level declaration of this syntax:

  • [ numeric_literal | (enumeration_constructor) ] more_name {parameters} = contents { | contents } ;
  • numeric_literal: It should be a natural number. Omitted is the same as zero.
  • enumeration_constructor: A constructor of the enumeration that was specified in the more-notation. If an enumeration is specified, the enumeration constructor is required here.
  • parameters: Lowercased names which will be scoped locally to this declaration. The number of parameters must match the number of parameters specified in the more-notation.
  • contents: The contents depends on where the more-notation is.

Semantics

In the place where the more-notation is, all contents of more-declarations of that name will be reordered and corrected before being placed in place of the more-notation.

Automatic reordering is overridden by the enumeration constructors or numeric literals in front of more-declarations.

Uses

Do-blocks

Case alternatives

Datatype declarations

A constructor definition in a data declaration is allowed to be replaced by a more-notation. Semantics of more-declarations becomes as follows:

  • Duplicate constructors are removed.
  • Duplicate constructors that do not match are errors.
  • Multiple constructors in a single more-declaration are guaranteed to keep the order given.

Example:

data T = Zero | more T deriving (Eq);
T = Two | Three | Four;
T = One | Two;

becomes

data T = Zero | One | Two | Three | Four deriving (Eq);

Fields in record syntax

Lists

Combining with Template Haskell

Uses in quotations

Manipulation in splices

Types and constructors