// bbldc_basicisma30360.h                                             -*-C++-*-
#ifndef INCLUDED_BBLDC_BASICISMA30360
#define INCLUDED_BBLDC_BASICISMA30360

#include <bsls_ident.h>
BSLS_IDENT("$Id: $")

//@PURPOSE: Provide stateless functions for the ISMA 30/360 convention.
//
//@CLASSES:
//  bbldc::BasicIsma30360: ISMA 30/360 convention stateless functions
//
//@DESCRIPTION: This component provides a `struct`, `bbldc::BasicIsma30360`,
// that serves as a namespace for defining a suite of date-related functions
// used to compute the day count and year fraction between two dates as per the
// ISMA 30/360 day-count convention.  In this day-count convention (also known
// as "European 30/360"), each year is assumed to have 12 months and 360 days,
// with each month consisting of exactly 30 days.  End-of-month rule
// adjustments are *not* made to account for the last day of February.
//
///ISMA 30/360 Day Count Algorithm
///-------------------------------
// Given `beginDate` and `endDate`, let:
// ```
// Ye =  year of earlier date           Yl =  year of later date
// Me = month of earlier date           Ml = month of later date
// De =   day of earlier date           Dl =   day of later date
//
//   o If De is 31, change De to 30.
//
//   o If Dl is 31, change Dl to 30.
//
// daysDiff ::= sign(endDate - beginDate) *
//                                   (Yl - Ye) * 360 + (Ml - Me) * 30 + Dl - De
// ```
// Reference: Formulae For Yield And Other Calculations (1992)
//            ISBN: 0-9515474-0-2
//
// Note that in this day-count convention, dates (`De` and `Dl`) are adjusted
// independently of each other.
//
// The year fraction is simply the day count divided by 360.
//
///Usage
///-----
// This section illustrates intended use of this component.
//
///Example 1: Computing Day Count and Year Fraction
/// - - - - - - - - - - - - - - - - - - - - - - - -
// The following snippets of code illustrate how to use `bbldc::BasicIsma30360`
// methods.  First, create two `bdlt::Date` variables, `d1` and `d2`:
// ```
// const bdlt::Date d1(2004,  9, 30);
// const bdlt::Date d2(2004, 12, 31);
// ```
// Then, compute the day count between the two dates:
// ```
// const int daysDiff = bbldc::BasicIsma30360::daysDiff(d1, d2);
// assert(90 == daysDiff);
// ```
// Finally, compute the year fraction between the two dates:
// ```
// const double yearsDiff = bbldc::BasicIsma30360::yearsDiff(d1, d2);
// assert(0.25 == yearsDiff);
// ```

#include <bblscm_version.h>

namespace BloombergLP {
namespace bdlt {

class Date;

}  // close namespace bdlt

namespace bbldc {

                          // =====================
                          // struct BasicIsma30360
                          // =====================

/// This `struct` provides a namespace for a suite of pure functions that
/// compute values based on dates according to the ISMA 30/360 day-count
/// convention.
struct BasicIsma30360 {

    // CLASS METHODS

    /// Return the (signed) number of days between the specified `beginDate`
    /// and `endDate` according to the ISMA 30/360 day-count convention.  If
    /// `beginDate <= endDate`, then the result is non-negative.  Note that
    /// reversing the order of `beginDate` and `endDate` negates the result.
    static int daysDiff(const bdlt::Date& beginDate,
                        const bdlt::Date& endDate);

    /// Return the (signed fractional) number of years between the specified
    /// `beginDate` and `endDate` according to the ISMA 30/360 day-count
    /// convention.  If `beginDate <= endDate`, then the result is
    /// non-negative.  Note that reversing the order of `beginDate` and
    /// `endDate` negates the result; specifically,
    /// `|yearsDiff(b, e) + yearsDiff(e, b)| <= 1.0e-15` for all dates `b`
    /// and `e`.
    static double yearsDiff(const bdlt::Date& beginDate,
                            const bdlt::Date& endDate);
};

}  // close package namespace
}  // close enterprise namespace

#endif

// ----------------------------------------------------------------------------
// Copyright 2015 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
