Temporal Expressions for Ruby
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Temporal Expressions for Ruby

TExp is a temporal expression library for Ruby with a modular, extensible expression serialization language.

Temporal expressions are a way of concisely expressing recuring events. For example, Christmas falls on the 25th of December every year. A temporal expression that represented the recurring event called “Christmas” would return true for any date that falls on the 25th of December.

dec25 = Date.parse("Dec 25, 2008")
christmas_texp.includes?(dec25)      # => true
christmas_texp.includes?(dec25 + 1)  # => false

Temporal expressions can be combined using operators. For example, if I have a temporal expression for Christmas and one for Thanksgiving, I can combine them into a single holiday expression thusly:

holidays_texp = christmas_texp + thanksgiving_texp

TExp Features

  • Basic Expressions for:

    • Day of Week (see DayOfWeek)

    • Day of Month (see DayOfMonth)

    • Week of Month (See Week)

    • Specific Month (See Month)

    • Specific Year (See Year)

  • Composite Expressions for:

    • Logical AND (date must be included by all sub-expressions)

    • Logical OR (date is included by any sub-expression)

    • Logical NOT (include any date not included in the sub-expression)

    • Windows (specify a windows of days around any date matching the sub-expression)

  • Human readable descriptions via inspect

  • Compact, parsable encoding via to_s

  • User expandable with custom temporal expression types, that interoperates with the compact, parsable encoding.

Examples

Match any Monday

te = TExp::DayOfWeek.new(Date::DAYNAMES.index("Monday"))
te.include?(Date.parse("Mar 3, 2008"))    # => true
te.include?(Date.parse("Mar 4, 2008"))    # => false
te.include?(Date.parse("Mar 10, 2008"))   # => true

Match any date in March

te = TExp::Month.new(3)
te.include?(Date.parse("Mar 1, 2008"))   # => true
te.include?(Date.parse("Mar 31, 2008"))  # => true
te.include?(Date.parse("Mar 15, 1995"))   # => true

te.include?(Date.parse("Feb 28, 2008"))   # => false

Match Valentine's day (any year)

te = TExp::And.new(
       TExp::DayOfMonth.new(14),
       TExp::Month.new(2))

 te.include?(Date.parse("Feb 14, 2008"))  # => true
 te.include?(Date.parse("Feb 14, 2007"))  # => true

Match Valentine's day in 2008

te = TExp::And.new(
       TExp::DayOfMonth.new(14),
       TExp::Month.new(2),
       TExp::Year.new(2008))

 te.include?(Date.parse("Feb 14, 2008"))  # => true
 te.include?(Date.parse("Feb 14, 2007"))  # => false

Match any Monday in March

te = TExp::And.new(
       TExp::Month.new(3),
       TExp::DayOfWeek.new(Date::DAYNAMES.index("Monday")))

te.include?(Date.parse("Mar 3, 2008"))    # => true
te.include?(Date.parse("Mar 10, 2008"))   # => true

te.include?(Date.parse("Mar 11, 2008"))   # => false
te.include?(Date.parse("Apr 7, 2008"))    # => false

Links

Documents

github.com/jimweirich/texp

Git Clone

git://github.com/jimweirich/texp.git

Issue Tracking

www.pivotaltracker.com/projects/42967

Bug Reporting

onestepback.org/cgi-bin/bugs.cgi?project=texp