Documentation
¶
Overview ¶
Package ruleset implements rules that can be used in combination with a rule based scanner.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ( // Default is the ruleset that this application uses by default. The rules // are inspired by Sqlite, however they do not care as much about // compatibility with other database systems, and are therefore simpler to // read and write. Default = Ruleset{ WhitespaceDetector: defaultWhitespaceDetector.Matches, LinefeedDetector: defaultLinefeedDetector.Matches, Rules: defaultRules, } )
Functions ¶
This section is empty.
Types ¶
type DetectorFunc ¶
DetectorFunc is a function that can detect if a given rune has a implementation specific attribute.
type FuncRule ¶
type FuncRule func(RuneScanner) (token.Type, bool)
FuncRule is an type alias that works as implementation for a ruleset.Rule.
func myRule(s RuneScanner) (token.Type, bool) { ... }
var _ Rule = FuncRule(myRule)
type Rule ¶
type Rule interface {
// Apply tries to apply this rule to the given RuneScanner. If the rule
// determines itself as not applicable to the current RuneScanner, return
// applicable=false, and the rule based scanner will handle everything else.
Apply(RuneScanner) (token token.Type, applicable bool)
}
Rule describes a single scanner rule that can theoretically be applied. If the rule is applicable, is decided by the rule itself. If it returns applicable=false, the it is the rule based scanner's responsibility, to reset its position information to where it was, before the rule was applied.
A rule takes a RuneScanner as parameter, which can be used to evaluate runes and advance the position pointer of the rule based scanner. After consuming n matching runes, return a token.Type. The rule based scanner will create a token from its position information, the consumed runes and the returned token.Type.
input := "hello"
...
func (r myRule) Apply(s RuneScanner) (token.Type, bool) {
r.ConsumeRune()
r.ConsumeRune()
r.ConsumeRune()
r.ConsumeRune()
r.ConsumeRune()
return token.Literal, true
}
The above example will cause the rule based scanner to emit a token with length=5, value=hello, offset=0.
To use a func(RuneScanner) (token.Type, bool) as Rule, see ruleset.FuncRule.
type Ruleset ¶
type Ruleset struct {
WhitespaceDetector DetectorFunc
LinefeedDetector DetectorFunc
Rules []Rule
}
Ruleset is a collection of a whitespace detector, a linefeed detector and a slice of rules. A rule based scanner can work with this to create tokens from the given rules.
type RuneScanner ¶
RuneScanner is a capsule that limits the interaction of the scanner to a subset of two core functions. It is not guaranteed that the value in this interface will always be of the same type. This implies, that you shouldn't place type assertions on this interface.
Source Files