Documentation
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Overview ¶
Package engine implements the isnow pattern engine: recognition of pattern source via the grammar repo's ANTLR-generated parser, the shorthand-ladder role assignment, compilation of every field term to a predicate, membership (Holds) over a broken-down instant, and occurrence derivation (Next/Prev) under the 100-year search horizon.
The root go-isnow package is a thin facade over this package: everything exported here is re-exported there unchanged, so external callers never import the engine directly. Errors are the internal/constants sentinels, matchable with errors.Is.
Index ¶
- func Code(err error) string
- func Is(src PatternText, at time.Time) (bool, error)
- type Pattern
- func (p Pattern) Canonical() string
- func (p Pattern) Explain() string
- func (p Pattern) Holds(at time.Time) bool
- func (p Pattern) Next(from time.Time) (time.Time, bool)
- func (p Pattern) NextContext(ctx context.Context, from time.Time) (time.Time, bool, error)
- func (p Pattern) Prev(from time.Time) (time.Time, bool)
- func (p Pattern) PrevContext(ctx context.Context, from time.Time) (time.Time, bool, error)
- func (p Pattern) String() string
- type PatternText
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Pattern ¶
type Pattern struct {
// contains filtered or unexported fields
}
Pattern is a parsed, canonicalized isnow. The zero value is not usable; obtain one from Parse. Patterns are immutable and safe to copy and share.
func Parse ¶
func Parse(src PatternText) (Pattern, error)
Parse recognizes src, resolves symbols and the shorthand ladder, and validates field domains. It returns one of constants.ErrSyntax, constants.ErrSymbol, constants.ErrRange, or constants.ErrContext.
func (Pattern) Explain ¶
Explain returns a deterministic English description of the isnow, built from the terminology vocabulary. The wording is implementation-defined (not pinned by the conformance corpus).
func (Pattern) Holds ¶
Holds reports whether the isnow holds at the instant: every field constraint and every bound is satisfied. The instant is evaluated in its own location (at.Location()) and truncated to whole seconds.
func (Pattern) Next ¶
Next returns the earliest occurrence strictly after from, or false when none exists within the pattern's window or the 100-year horizon.
func (Pattern) NextContext ¶
NextContext is Next with cancellation: the search aborts and returns ctx's error when the context is done, so an unbounded scan on a pathological pattern (e.g. an impossible bounded window) cannot pin a CPU indefinitely. The context is checked once per civil day, bounding a cancelled search to at most a single day's enumeration.
func (Pattern) PrevContext ¶
PrevContext is Prev with cancellation (see NextContext).
type PatternText ¶
type PatternText string
PatternText is isnow pattern source text accepted by Parse. It is exported so callers in other packages can convert their string input at the call site.
Source Files