RegExDot.Meta

AUTHOR

Dr. Alistair Ward

DESCRIPTION

• Describes the set of polymorphic data, which can be matched.
• Only permits a match against exactly one polymorphic datum, which distinguishes it from a zero-width assertion, like an anchor, word-boundary, or look-ahead assertion.
• Designed to be used by a polymorphic regex-engine, to implement the traditional meta-characters; . [] [^].
• Permits Perl-style shortcuts for commonly used Meta-data, to be canned & assigned a single-Char mnemonic for subsequent reference; the implementation of Read looks for a back-slashed Char, for which it expects there to be a corresponding canned Meta. Since this class is polymorphic, it has no knowledge of what shortcuts might be appropriate for the chosen type-parameter, so the expansion from the back-slashed Char to corresponding Meta-data, is performed through the expand interface of the ShortcutExpander class, which should be implemented elsewhere.

Type-classes

class ShortcutExpander m => ShortcutExpander m where

• The interface via which Perl-style shortcuts are expanded, in a manner appropriate to the chosen type-parameter.
• Since the expansion of Perl-style shortcuts, is more restricted inside than outside a BracketExpression, the former is considered to be a superclass, providing a base from which to build alternative implementations.

Methods

expand

Arguments

:: Char

-> Meta m

Expand a Perl-style shortcut.

Instances

ShortcutExpander Int

Types

Data-types

data Meta m

Declares a polymorphic data-type.

Constructors

Any

Any datum matches. Equivalent to NoneOf [], but more efficient. CAVEAT: independent of the type-parameter a.

Literal m

The datum matches, if it's equal to the specified value. Equivalent to AnyOf [BracketExpression.Literal x], but more efficient.

AnyOf (BracketExpression m)

The datum matches, if containsMatch.

NoneOf (BracketExpression m)

The datum matches, if not BracketExpression.containsMatch.

Predicate (ShowablePredicate m)

The datum matches if ShowablePredicate.

Instances

Eq m => Eq (Meta m)

(ShortcutExpander m, Read m) => Read (Meta m)

Show m => Show (Meta m)

NFData m => NFData (Meta m)

SelfValidator (Meta m)

Consumer (Meta m)

Constants

shortcutToken :: Char

The token used to precede a Perl-style shortcut, when in the String-form.

anyToken :: Char

The token used to denote Any, when in the String-form.

tokens :: String

The set of Char to which a specific meaning is attributed, when reading from String.

Functions

Predicates

isMatch

Arguments

:: Eq m

=> m

The input datum.

-> Meta m

The meta-entity against which the input datum is to be matched.

-> Bool

The result of the match-operation.

True if the specified datum matches.