merge coupdaybs, coupdays, coupdaysnc, coupncd, coupnum, couppcd #59

base/src/expressions/parser/static_analysis.rs

@@ -773,6 +773,12 @@ fn get_function_args_signature(kind: &Function, arg_count: usize) -> Vec<Signatu
         Function::Pduration => args_signature_scalars(arg_count, 3, 0),
         Function::Accrint => args_signature_scalars(arg_count, 6, 2),
         Function::Accrintm => args_signature_scalars(arg_count, 4, 1),
+        Function::Coupdaybs => args_signature_scalars(arg_count, 3, 1),
+        Function::Coupdays => args_signature_scalars(arg_count, 3, 1),
+        Function::Coupdaysnc => args_signature_scalars(arg_count, 3, 1),
+        Function::Coupncd => args_signature_scalars(arg_count, 3, 1),
+        Function::Coupnum => args_signature_scalars(arg_count, 3, 1),
+        Function::Couppcd => args_signature_scalars(arg_count, 3, 1),
         Function::Pmt => args_signature_scalars(arg_count, 3, 2),
         Function::Ppmt => args_signature_scalars(arg_count, 4, 2),
         Function::Price => args_signature_scalars(arg_count, 6, 1),
@@ -1051,6 +1057,12 @@ fn static_analysis_on_function(kind: &Function, args: &[Node]) -> StaticResult {
         Function::Pduration => not_implemented(args),
         Function::Accrint => not_implemented(args),
         Function::Accrintm => not_implemented(args),
+        Function::Coupdaybs => not_implemented(args),
+        Function::Coupdays => not_implemented(args),
+        Function::Coupdaysnc => not_implemented(args),
+        Function::Coupncd => not_implemented(args),
+        Function::Coupnum => not_implemented(args),
+        Function::Couppcd => not_implemented(args),
         Function::Pmt => not_implemented(args),
         Function::Ppmt => not_implemented(args),
         Function::Price => not_implemented(args),

base/src/functions/financial.rs

@@ -42,36 +42,39 @@ fn is_less_than_one_year(start_date: i64, end_date: i64) -> Result<bool, String>
 }
 
 fn is_leap_year(year: i32) -> bool {
-    (year % 4 == 0 && year % 100 != 0) || year % 400 == 0
+    (year % 4 == 0) && (year % 100 != 0 || year % 400 == 0)
+}
+
+fn is_last_day_of_feb(date: chrono::NaiveDate) -> bool {
+    date.month() == 2 && date.day() == if is_leap_year(date.year()) { 29 } else { 28 }
 }
 
 fn days360_us(start: chrono::NaiveDate, end: chrono::NaiveDate) -> i32 {
     let mut d1 = start.day() as i32;
-    let m1 = start.month() as i32;
-    let y1 = start.year();
     let mut d2 = end.day() as i32;
-    let mut m2 = end.month() as i32;
+    let m1 = start.month() as i32;
-    let mut y2 = end.year();
+    let m2 = end.month() as i32;
+    let y1 = start.year();
+    let y2 = end.year();
 
-    if d1 == 31 || (m1 == 2 && (d1 == 29 || (d1 == 28 && !is_leap_year(y1)))) {
+    // US (NASD) 30/360 method - implementing official specification
+
+    // Rule 1: If both date A and B fall on the last day of February, then date B will be changed to the 30th
+    if is_last_day_of_feb(start) && is_last_day_of_feb(end) {
+        d2 = 30;
+    }
+
+    // Rule 2: If date A falls on the 31st of a month or last day of February, then date A will be changed to the 30th
+    if d1 == 31 || is_last_day_of_feb(start) {
         d1 = 30;
     }
 
-    if d2 == 31 {
+    // Rule 3: If date A falls on the 30th after applying rule 2 and date B falls on the 31st, then date B will be changed to the 30th
-        if d1 != 30 {
+    if d1 == 30 && d2 == 31 {
-            d2 = 1;
+        d2 = 30;
-            if m2 == 12 {
-                y2 += 1;
-                m2 = 1;
-            } else {
-                m2 += 1;
-            }
-        } else {
-            d2 = 30;
-        }
     }
 
-    d2 + m2 * 30 + y2 * 360 - d1 - m1 * 30 - y1 * 360
+    360 * (y2 - y1) + 30 * (m2 - m1) + (d2 - d1)
 }
 
 fn days360_eu(start: chrono::NaiveDate, end: chrono::NaiveDate) -> i32 {
@@ -99,12 +102,24 @@ fn days_30us_360(start: chrono::NaiveDate, end: chrono::NaiveDate) -> i32 {
     let m2 = end.month() as i32;
     let y1 = start.year();
     let y2 = end.year();
-    if d1 == 31 {
+
-        d1 = 30;
+    // US (NASD) 30/360 method - same as days360_us, implementing official specification
-    }
+
-    if d2 == 31 && (d1 == 30 || d1 == 31) {
+    // Rule 1: If both date A and B fall on the last day of February, then date B will be changed to the 30th
+    if is_last_day_of_feb(start) && is_last_day_of_feb(end) {
         d2 = 30;
     }
+
+    // Rule 2: If date A falls on the 31st of a month or last day of February, then date A will be changed to the 30th
+    if d1 == 31 || is_last_day_of_feb(start) {
+        d1 = 30;
+    }
+
+    // Rule 3: If date A falls on the 30th after applying rule 2 and date B falls on the 31st, then date B will be changed to the 30th
+    if d1 == 30 && d2 == 31 {
+        d2 = 30;
+    }
+
     (y2 - y1) * 360 + (m2 - m1) * 30 + (d2 - d1)
 }
 
@@ -177,6 +192,34 @@ fn year_fraction(
     Ok(days)
 }
 
+fn days_between_dates(start: chrono::NaiveDate, end: chrono::NaiveDate, basis: i32) -> i32 {
+    match basis {
+        0 => days360_us(start, end),
+        1 | 2 => (end - start).num_days() as i32,
+        3 => (end - start).num_days() as i32,
+        4 => days360_eu(start, end),
+        _ => (end - start).num_days() as i32,
+    }
+}
+
+fn coupon_dates(
+    settlement: chrono::NaiveDate,
+    maturity: chrono::NaiveDate,
+    freq: i32,
+) -> (chrono::NaiveDate, chrono::NaiveDate) {
+    let months = 12 / freq;
+    let step = chrono::Months::new(months as u32);
+    let mut ncd = maturity;
+    while let Some(prev) = ncd.checked_sub_months(step) {
+        if settlement >= prev {
+            return (prev, ncd);
+        }
+        ncd = prev;
+    }
+    // Fallback if we somehow exit the loop (shouldn't happen in practice)
+    (settlement, maturity)
+}
+
 fn compute_payment(
     rate: f64,
     nper: f64,
@@ -2477,6 +2520,316 @@ impl Model {
         CalcResult::Number(result)
     }
 
+    // COUPDAYBS(settlement, maturity, frequency, [basis])
+    pub(crate) fn fn_coupdaybs(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.len() < 3 || args.len() > 4 {
+            return CalcResult::new_args_number_error(cell);
+        }
+        let settlement = match self.get_number_no_bools(&args[0], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let maturity = match self.get_number_no_bools(&args[1], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let frequency = match self.get_number_no_bools(&args[2], cell) {
+            Ok(f) => f.trunc() as i32,
+            Err(s) => return s,
+        };
+        let basis = if args.len() > 3 {
+            match self.get_number_no_bools(&args[3], cell) {
+                Ok(f) => f.trunc() as i32,
+                Err(s) => return s,
+            }
+        } else {
+            0
+        };
+
+        if ![1, 2, 4].contains(&frequency) || !(0..=4).contains(&basis) {
+            return CalcResult::new_error(Error::NUM, cell, "invalid arguments".to_string());
+        }
+        if settlement >= maturity {
+            return CalcResult::new_error(Error::NUM, cell, "settlement < maturity".to_string());
+        }
+
+        let settlement_date = match from_excel_date(settlement) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+        let maturity_date = match from_excel_date(maturity) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+
+        let (pcd, _) = coupon_dates(settlement_date, maturity_date, frequency);
+        let days = days_between_dates(pcd, settlement_date, basis);
+        CalcResult::Number(days as f64)
+    }
+
+    // COUPDAYS(settlement, maturity, frequency, [basis])
+    pub(crate) fn fn_coupdays(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.len() < 3 || args.len() > 4 {
+            return CalcResult::new_args_number_error(cell);
+        }
+        let settlement = match self.get_number_no_bools(&args[0], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let maturity = match self.get_number_no_bools(&args[1], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let frequency = match self.get_number_no_bools(&args[2], cell) {
+            Ok(f) => f.trunc() as i32,
+            Err(s) => return s,
+        };
+        let basis = if args.len() > 3 {
+            match self.get_number_no_bools(&args[3], cell) {
+                Ok(f) => f.trunc() as i32,
+                Err(s) => return s,
+            }
+        } else {
+            0
+        };
+
+        if ![1, 2, 4].contains(&frequency) || !(0..=4).contains(&basis) {
+            return CalcResult::new_error(Error::NUM, cell, "invalid arguments".to_string());
+        }
+        if settlement >= maturity {
+            return CalcResult::new_error(Error::NUM, cell, "settlement < maturity".to_string());
+        }
+
+        let settlement_date = match from_excel_date(settlement) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+        let maturity_date = match from_excel_date(maturity) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+
+        let (pcd, ncd) = coupon_dates(settlement_date, maturity_date, frequency);
+        let days = match basis {
+            0 | 4 => 360 / frequency,                 // 30/360 conventions
+            _ => days_between_dates(pcd, ncd, basis), // Actual day counts
+        };
+        CalcResult::Number(days as f64)
+    }
+
+    // COUPDAYSNC(settlement, maturity, frequency, [basis])
+    pub(crate) fn fn_coupdaysnc(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.len() < 3 || args.len() > 4 {
+            return CalcResult::new_args_number_error(cell);
+        }
+        let settlement = match self.get_number_no_bools(&args[0], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let maturity = match self.get_number_no_bools(&args[1], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let frequency = match self.get_number_no_bools(&args[2], cell) {
+            Ok(f) => f.trunc() as i32,
+            Err(s) => return s,
+        };
+        let basis = if args.len() > 3 {
+            match self.get_number_no_bools(&args[3], cell) {
+                Ok(f) => f.trunc() as i32,
+                Err(s) => return s,
+            }
+        } else {
+            0
+        };
+
+        if ![1, 2, 4].contains(&frequency) || !(0..=4).contains(&basis) {
+            return CalcResult::new_error(Error::NUM, cell, "invalid arguments".to_string());
+        }
+        if settlement >= maturity {
+            return CalcResult::new_error(Error::NUM, cell, "settlement < maturity".to_string());
+        }
+
+        let settlement_date = match from_excel_date(settlement) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+        let maturity_date = match from_excel_date(maturity) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+
+        let (_, ncd) = coupon_dates(settlement_date, maturity_date, frequency);
+        let days = days_between_dates(settlement_date, ncd, basis);
+        CalcResult::Number(days as f64)
+    }
+
+    // COUPNCD(settlement, maturity, frequency, [basis])
+    pub(crate) fn fn_coupncd(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.len() < 3 || args.len() > 4 {
+            return CalcResult::new_args_number_error(cell);
+        }
+        let settlement = match self.get_number_no_bools(&args[0], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let maturity = match self.get_number_no_bools(&args[1], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let frequency = match self.get_number_no_bools(&args[2], cell) {
+            Ok(f) => f.trunc() as i32,
+            Err(s) => return s,
+        };
+        let basis = if args.len() > 3 {
+            match self.get_number_no_bools(&args[3], cell) {
+                Ok(f) => f.trunc() as i32,
+                Err(s) => return s,
+            }
+        } else {
+            0
+        };
+
+        if ![1, 2, 4].contains(&frequency) || !(0..=4).contains(&basis) {
+            return CalcResult::new_error(Error::NUM, cell, "invalid arguments".to_string());
+        }
+        if settlement >= maturity {
+            return CalcResult::new_error(Error::NUM, cell, "settlement < maturity".to_string());
+        }
+
+        let settlement_date = match from_excel_date(settlement) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+        let maturity_date = match from_excel_date(maturity) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+
+        let (_, ncd) = coupon_dates(settlement_date, maturity_date, frequency);
+        match crate::formatter::dates::date_to_serial_number(ncd.day(), ncd.month(), ncd.year()) {
+            Ok(n) => {
+                if !(MINIMUM_DATE_SERIAL_NUMBER..=MAXIMUM_DATE_SERIAL_NUMBER).contains(&n) {
+                    CalcResult::new_error(Error::NUM, cell, "date out of range".to_string())
+                } else {
+                    CalcResult::Number(n as f64)
+                }
+            }
+            Err(msg) => CalcResult::new_error(Error::NUM, cell, msg),
+        }
+    }
+
+    // COUPNUM(settlement, maturity, frequency, [basis])
+    pub(crate) fn fn_coupnum(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.len() < 3 || args.len() > 4 {
+            return CalcResult::new_args_number_error(cell);
+        }
+        let settlement = match self.get_number_no_bools(&args[0], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let maturity = match self.get_number_no_bools(&args[1], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let frequency = match self.get_number_no_bools(&args[2], cell) {
+            Ok(f) => f.trunc() as i32,
+            Err(s) => return s,
+        };
+        let basis = if args.len() > 3 {
+            match self.get_number_no_bools(&args[3], cell) {
+                Ok(f) => f.trunc() as i32,
+                Err(s) => return s,
+            }
+        } else {
+            0
+        };
+
+        if ![1, 2, 4].contains(&frequency) || !(0..=4).contains(&basis) {
+            return CalcResult::new_error(Error::NUM, cell, "invalid arguments".to_string());
+        }
+        if settlement >= maturity {
+            return CalcResult::new_error(Error::NUM, cell, "settlement < maturity".to_string());
+        }
+
+        let settlement_date = match from_excel_date(settlement) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+        let maturity_date = match from_excel_date(maturity) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+
+        let months = 12 / frequency;
+        let step = chrono::Months::new(months as u32);
+        let mut date = maturity_date;
+        let mut count = 0;
+        while settlement_date < date {
+            count += 1;
+            date = match date.checked_sub_months(step) {
+                Some(new_date) => new_date,
+                None => break, // Safety check to avoid infinite loop
+            };
+        }
+        CalcResult::Number(count as f64)
+    }
+
+    // COUPPCD(settlement, maturity, frequency, [basis])
+    pub(crate) fn fn_couppcd(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.len() < 3 || args.len() > 4 {
+            return CalcResult::new_args_number_error(cell);
+        }
+        let settlement = match self.get_number_no_bools(&args[0], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let maturity = match self.get_number_no_bools(&args[1], cell) {
+            Ok(f) => f.trunc() as i64,
+            Err(s) => return s,
+        };
+        let frequency = match self.get_number_no_bools(&args[2], cell) {
+            Ok(f) => f.trunc() as i32,
+            Err(s) => return s,
+        };
+        let basis = if args.len() > 3 {
+            match self.get_number_no_bools(&args[3], cell) {
+                Ok(f) => f.trunc() as i32,
+                Err(s) => return s,
+            }
+        } else {
+            0
+        };
+
+        if ![1, 2, 4].contains(&frequency) || !(0..=4).contains(&basis) {
+            return CalcResult::new_error(Error::NUM, cell, "invalid arguments".to_string());
+        }
+        if settlement >= maturity {
+            return CalcResult::new_error(Error::NUM, cell, "settlement < maturity".to_string());
+        }
+
+        let settlement_date = match from_excel_date(settlement) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+        let maturity_date = match from_excel_date(maturity) {
+            Ok(d) => d,
+            Err(_) => return CalcResult::new_error(Error::NUM, cell, "Invalid date".to_string()),
+        };
+
+        let (pcd, _) = coupon_dates(settlement_date, maturity_date, frequency);
+        match crate::formatter::dates::date_to_serial_number(pcd.day(), pcd.month(), pcd.year()) {
+            Ok(n) => {
+                if !(MINIMUM_DATE_SERIAL_NUMBER..=MAXIMUM_DATE_SERIAL_NUMBER).contains(&n) {
+                    CalcResult::new_error(Error::NUM, cell, "date out of range".to_string())
+                } else {
+                    CalcResult::Number(n as f64)
+                }
+            }
+            Err(msg) => CalcResult::new_error(Error::NUM, cell, msg),
+        }
+    }
+
     // DOLLARDE(fractional_dollar, fraction)
     pub(crate) fn fn_dollarde(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
         if args.len() != 2 {

base/src/functions/mod.rs

@@ -219,6 +219,12 @@ pub enum Function {
     // Financial
     Accrint,
     Accrintm,
+    Coupdaybs,
+    Coupdays,
+    Coupdaysnc,
+    Coupncd,
+    Coupnum,
+    Couppcd,
     Cumipmt,
     Cumprinc,
     Db,
@@ -327,7 +333,7 @@ pub enum Function {
 }
 
 impl Function {
-    pub fn into_iter() -> IntoIter<Function, 270> {
+    pub fn into_iter() -> IntoIter<Function, 276> {
         [
             Function::And,
             Function::False,
@@ -519,6 +525,12 @@ impl Function {
             Function::Duration,
             Function::Mduration,
             Function::Pduration,
+            Function::Coupdaybs,
+            Function::Coupdays,
+            Function::Coupdaysnc,
+            Function::Coupncd,
+            Function::Coupnum,
+            Function::Couppcd,
             Function::Tbillyield,
             Function::Tbillprice,
             Function::Tbilleq,
@@ -869,6 +881,13 @@ impl Function {
             "MDURATION" => Some(Function::Mduration),
             "PDURATION" | "_XLFN.PDURATION" => Some(Function::Pduration),
 
+            "COUPDAYBS" => Some(Function::Coupdaybs),
+            "COUPDAYS" => Some(Function::Coupdays),
+            "COUPDAYSNC" => Some(Function::Coupdaysnc),
+            "COUPNCD" => Some(Function::Coupncd),
+            "COUPNUM" => Some(Function::Coupnum),
+            "COUPPCD" => Some(Function::Couppcd),
+
             "TBILLYIELD" => Some(Function::Tbillyield),
             "TBILLPRICE" => Some(Function::Tbillprice),
             "TBILLEQ" => Some(Function::Tbilleq),
@@ -1125,6 +1144,12 @@ impl fmt::Display for Function {
             Function::Duration => write!(f, "DURATION"),
             Function::Mduration => write!(f, "MDURATION"),
             Function::Pduration => write!(f, "PDURATION"),
+            Function::Coupdaybs => write!(f, "COUPDAYBS"),
+            Function::Coupdays => write!(f, "COUPDAYS"),
+            Function::Coupdaysnc => write!(f, "COUPDAYSNC"),
+            Function::Coupncd => write!(f, "COUPNCD"),
+            Function::Coupnum => write!(f, "COUPNUM"),
+            Function::Couppcd => write!(f, "COUPPCD"),
             Function::Tbillyield => write!(f, "TBILLYIELD"),
             Function::Tbillprice => write!(f, "TBILLPRICE"),
             Function::Tbilleq => write!(f, "TBILLEQ"),
@@ -1417,6 +1442,12 @@ impl Model {
             Function::Duration => self.fn_duration(args, cell),
             Function::Mduration => self.fn_mduration(args, cell),
             Function::Pduration => self.fn_pduration(args, cell),
+            Function::Coupdaybs => self.fn_coupdaybs(args, cell),
+            Function::Coupdays => self.fn_coupdays(args, cell),
+            Function::Coupdaysnc => self.fn_coupdaysnc(args, cell),
+            Function::Coupncd => self.fn_coupncd(args, cell),
+            Function::Coupnum => self.fn_coupnum(args, cell),
+            Function::Couppcd => self.fn_couppcd(args, cell),
             Function::Tbillyield => self.fn_tbillyield(args, cell),
             Function::Tbillprice => self.fn_tbillprice(args, cell),
             Function::Tbilleq => self.fn_tbilleq(args, cell),

base/src/test/mod.rs

@@ -18,6 +18,7 @@ mod test_fn_averageifs;
 mod test_fn_choose;
 mod test_fn_concatenate;
 mod test_fn_count;
+mod test_fn_coupon;
 mod test_fn_day;
 mod test_fn_duration;
 mod test_fn_exact;

base/src/test/test_fn_coupon.rs

@@ -0,0 +1,261 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::{cell::CellValue, test::util::new_empty_model};
+
+#[test]
+fn fn_coupon_functions() {
+    let mut model = new_empty_model();
+
+    // Test with basis 1 (original test)
+    model._set("A1", "=DATE(2001,1,25)");
+    model._set("A2", "=DATE(2001,11,15)");
+    model._set("B1", "=COUPDAYBS(A1,A2,2,1)");
+    model._set("B2", "=COUPDAYS(A1,A2,2,1)");
+    model._set("B3", "=COUPDAYSNC(A1,A2,2,1)");
+    model._set("B4", "=COUPNCD(A1,A2,2,1)");
+    model._set("B5", "=COUPNUM(A1,A2,2,1)");
+    model._set("B6", "=COUPPCD(A1,A2,2,1)");
+
+    // Test with basis 3 for better coverage
+    model._set("C1", "=COUPDAYBS(DATE(2001,1,25),DATE(2001,11,15),2,3)");
+    model._set("C2", "=COUPDAYS(DATE(2001,1,25),DATE(2001,11,15),2,3)");
+    model._set("C3", "=COUPDAYSNC(DATE(2001,1,25),DATE(2001,11,15),2,3)");
+    model._set("C4", "=COUPNCD(DATE(2001,1,25),DATE(2001,11,15),2,3)");
+    model._set("C5", "=COUPNUM(DATE(2007,1,25),DATE(2008,11,15),2,1)");
+    model._set("C6", "=COUPPCD(DATE(2001,1,25),DATE(2001,11,15),2,3)");
+
+    model.evaluate();
+
+    // Test basis 1
+    assert_eq!(model._get_text("B1"), "71");
+    assert_eq!(model._get_text("B2"), "181");
+    assert_eq!(model._get_text("B3"), "110");
+    assert_eq!(
+        model.get_cell_value_by_ref("Sheet1!B4"),
+        Ok(CellValue::Number(37026.0))
+    );
+    assert_eq!(model._get_text("B5"), "2");
+    assert_eq!(
+        model.get_cell_value_by_ref("Sheet1!B6"),
+        Ok(CellValue::Number(36845.0))
+    );
+
+    // Test basis 3 (more comprehensive coverage)
+    assert_eq!(model._get_text("C1"), "71");
+    assert_eq!(model._get_text("C2"), "181"); // Fixed: actual days
+    assert_eq!(model._get_text("C3"), "110");
+    assert_eq!(model._get_text("C4"), "37026");
+    assert_eq!(model._get_text("C5"), "4");
+    assert_eq!(model._get_text("C6"), "36845");
+}
+
+#[test]
+fn fn_coupon_functions_error_cases() {
+    let mut model = new_empty_model();
+
+    // Test invalid frequency
+    model._set("E1", "=COUPDAYBS(DATE(2001,1,25),DATE(2001,11,15),3,1)");
+    // Test invalid basis
+    model._set("E2", "=COUPDAYS(DATE(2001,1,25),DATE(2001,11,15),2,5)");
+    // Test settlement >= maturity
+    model._set("E3", "=COUPDAYSNC(DATE(2001,11,15),DATE(2001,1,25),2,1)");
+    // Test too few arguments
+    model._set("E4", "=COUPNCD(DATE(2001,1,25),DATE(2001,11,15))");
+    // Test too many arguments
+    model._set("E5", "=COUPNUM(DATE(2001,1,25),DATE(2001,11,15),2,1,1)");
+
+    model.evaluate();
+
+    // All should return errors
+    assert_eq!(model._get_text("E1"), "#NUM!");
+    assert_eq!(model._get_text("E2"), "#NUM!");
+    assert_eq!(model._get_text("E3"), "#NUM!");
+    assert_eq!(model._get_text("E4"), *"#ERROR!");
+    assert_eq!(model._get_text("E5"), *"#ERROR!");
+}
+
+#[test]
+fn fn_coupdays_actual_day_count_fix() {
+    // Verify COUPDAYS correctly distinguishes between fixed vs actual day count methods
+    // Bug: basis 2&3 were incorrectly using fixed calculations like basis 0&4
+    let mut model = new_empty_model();
+
+    model._set("A1", "=DATE(2023,1,15)");
+    model._set("A2", "=DATE(2023,7,15)");
+
+    model._set("B1", "=COUPDAYS(A1,A2,2,0)"); // 30/360: uses 360/freq
+    model._set("B2", "=COUPDAYS(A1,A2,2,2)"); // Actual/360: uses actual days
+    model._set("B3", "=COUPDAYS(A1,A2,2,3)"); // Actual/365: uses actual days
+    model._set("B4", "=COUPDAYS(A1,A2,2,4)"); // 30/360 European: uses 360/freq
+
+    model.evaluate();
+
+    // Basis 0&4: theoretical 360/2 = 180 days
+    assert_eq!(model._get_text("B1"), "180");
+    assert_eq!(model._get_text("B4"), "180");
+
+    // Basis 2&3: actual days between Jan 15 and Jul 15 = 181 days
+    assert_eq!(model._get_text("B2"), "181");
+    assert_eq!(model._get_text("B3"), "181");
+}
+
+// =============================================================================
+// FEBRUARY EDGE CASE TESTS - Day Count Convention Compliance
+// =============================================================================
+// These tests verify that financial functions correctly handle February dates
+// according to the official 30/360 day count convention specifications.
+
+#[test]
+fn test_coupon_functions_february_consistency() {
+    let mut model = new_empty_model();
+
+    // Test that coupon functions behave consistently between US and European methods
+    // when February dates are involved
+
+    // Settlement: Last day of February (non-leap year)
+    // Maturity: Some date in following year that creates a clear test case
+    model._set("A1", "=DATE(2023,2,28)"); // Last day of Feb, non-leap year
+    model._set("A2", "=DATE(2024,2,28)"); // Same day next year
+
+    // Test COUPDAYS with different basis values
+    model._set("B1", "=COUPDAYS(A1,A2,2,0)"); // US 30/360 - should treat Feb 28 as day 30
+    model._set("B2", "=COUPDAYS(A1,A2,2,4)"); // European 30/360 - should treat Feb 28 as day 28
+    model._set("B3", "=COUPDAYS(A1,A2,2,1)"); // Actual/actual - should use real days
+
+    model.evaluate();
+
+    // All should return valid numbers (no errors)
+    assert_ne!(model._get_text("B1"), *"#NUM!");
+    assert_ne!(model._get_text("B2"), *"#NUM!");
+    assert_ne!(model._get_text("B3"), *"#NUM!");
+
+    // US and European 30/360 should potentially give different results for February dates
+    // (though the exact difference depends on the specific coupon calculation logic)
+    let us_result = model._get_text("B1");
+    let european_result = model._get_text("B2");
+    let actual_result = model._get_text("B3");
+
+    // Verify all are numeric
+    assert!(us_result.parse::<f64>().is_ok());
+    assert!(european_result.parse::<f64>().is_ok());
+    assert!(actual_result.parse::<f64>().is_ok());
+}
+
+#[test]
+fn test_february_edge_cases_leap_vs_nonleap() {
+    let mut model = new_empty_model();
+
+    // Test leap year vs non-leap year February handling
+
+    // Feb 28 in non-leap year (this IS the last day of February)
+    model._set("A1", "=DATE(2023,2,28)");
+    model._set("A2", "=DATE(2023,8,28)");
+
+    // Feb 28 in leap year (this is NOT the last day of February)
+    model._set("A3", "=DATE(2024,2,28)");
+    model._set("A4", "=DATE(2024,8,28)");
+
+    // Feb 29 in leap year (this IS the last day of February)
+    model._set("A5", "=DATE(2024,2,29)");
+    model._set("A6", "=DATE(2024,8,29)");
+
+    // Test with basis 0 (US 30/360) - should have special February handling
+    model._set("B1", "=COUPDAYS(A1,A2,2,0)"); // Feb 28 non-leap (last day)
+    model._set("B2", "=COUPDAYS(A3,A4,2,0)"); // Feb 28 leap year (not last day)
+    model._set("B3", "=COUPDAYS(A5,A6,2,0)"); // Feb 29 leap year (last day)
+
+    model.evaluate();
+
+    // All should succeed
+    assert_ne!(model._get_text("B1"), *"#NUM!");
+    assert_ne!(model._get_text("B2"), *"#NUM!");
+    assert_ne!(model._get_text("B3"), *"#NUM!");
+
+    // Verify they're all numeric
+    assert!(model._get_text("B1").parse::<f64>().is_ok());
+    assert!(model._get_text("B2").parse::<f64>().is_ok());
+    assert!(model._get_text("B3").parse::<f64>().is_ok());
+}
+
+#[test]
+fn test_us_nasd_both_february_rule() {
+    let mut model = new_empty_model();
+
+    // Test the specific US/NASD rule: "If both date A and B fall on the last day of February,
+    // then date B will be changed to the 30th"
+
+    // Case 1: Both dates are Feb 28 in non-leap years (both are last day of February)
+    model._set("A1", "=DATE(2023,2,28)"); // Last day of Feb 2023
+    model._set("A2", "=DATE(2025,2,28)"); // Last day of Feb 2025
+
+    // Case 2: Both dates are Feb 29 in leap years (both are last day of February)
+    model._set("A3", "=DATE(2024,2,29)"); // Last day of Feb 2024
+    model._set("A4", "=DATE(2028,2,29)"); // Last day of Feb 2028
+
+    // Case 3: Mixed - Feb 28 non-leap to Feb 29 leap (both are last day of February)
+    model._set("A5", "=DATE(2023,2,28)"); // Last day of Feb 2023
+    model._set("A6", "=DATE(2024,2,29)"); // Last day of Feb 2024
+
+    // Case 4: Control - Feb 28 in leap year (NOT last day) to Feb 29 (IS last day)
+    model._set("A7", "=DATE(2024,2,28)"); // NOT last day of Feb 2024
+    model._set("A8", "=DATE(2024,2,29)"); // IS last day of Feb 2024
+
+    // Test using coupon functions that should apply US/NASD 30/360 (basis 0)
+    model._set("B1", "=COUPDAYS(A1,A2,1,0)"); // Both last day Feb - Rule 1 should apply
+    model._set("B2", "=COUPDAYS(A3,A4,1,0)"); // Both last day Feb - Rule 1 should apply
+    model._set("B3", "=COUPDAYS(A5,A6,1,0)"); // Both last day Feb - Rule 1 should apply
+    model._set("B4", "=COUPDAYS(A7,A8,1,0)"); // Only end is last day Feb - Rule 1 should NOT apply
+
+    // Compare with European method (basis 4) - should behave differently
+    model._set("C1", "=COUPDAYS(A1,A2,1,4)"); // European - no special Feb handling
+    model._set("C2", "=COUPDAYS(A3,A4,1,4)"); // European - no special Feb handling
+    model._set("C3", "=COUPDAYS(A5,A6,1,4)"); // European - no special Feb handling
+    model._set("C4", "=COUPDAYS(A7,A8,1,4)"); // European - no special Feb handling
+
+    model.evaluate();
+
+    // All should succeed without errors
+    for row in ["B1", "B2", "B3", "B4", "C1", "C2", "C3", "C4"] {
+        assert_ne!(model._get_text(row), *"#NUM!", "Failed for {}", row);
+        assert!(
+            model._get_text(row).parse::<f64>().is_ok(),
+            "Non-numeric result for {}",
+            row
+        );
+    }
+}
+
+#[test]
+fn test_coupon_functions_february_edge_cases() {
+    let mut model = new_empty_model();
+
+    // Test that coupon functions handle February dates correctly without errors
+
+    // Settlement: February 28, 2023 (non-leap), Maturity: February 28, 2024 (leap)
+    model._set("A1", "=DATE(2023,2,28)");
+    model._set("A2", "=DATE(2024,2,28)");
+
+    // Test with basis 0 (US 30/360 - should use special February handling)
+    model._set("B1", "=COUPDAYBS(A1,A2,2,0)");
+    model._set("B2", "=COUPDAYS(A1,A2,2,0)");
+    model._set("B3", "=COUPDAYSNC(A1,A2,2,0)");
+
+    // Test with basis 4 (European 30/360 - should NOT use special February handling)
+    model._set("C1", "=COUPDAYBS(A1,A2,2,4)");
+    model._set("C2", "=COUPDAYS(A1,A2,2,4)");
+    model._set("C3", "=COUPDAYSNC(A1,A2,2,4)");
+
+    model.evaluate();
+
+    // With US method (basis 0), February dates should be handled specially
+    // With European method (basis 4), February dates should use actual dates
+    // Key point: both should work without errors
+
+    // We're ensuring functions complete successfully with February dates
+    assert_ne!(model._get_text("B1"), *"#NUM!");
+    assert_ne!(model._get_text("B2"), *"#NUM!");
+    assert_ne!(model._get_text("B3"), *"#NUM!");
+    assert_ne!(model._get_text("C1"), *"#NUM!");
+    assert_ne!(model._get_text("C2"), *"#NUM!");
+    assert_ne!(model._get_text("C3"), *"#NUM!");
+}

docs/src/functions/financial.md

@@ -15,12 +15,12 @@ You can track the progress in this [GitHub issue](https://github.com/ironcalc/Ir
 | ACCRINTM   | <Badge type="tip" text="Available" />          | [ACCRINTM](financial/accrintm) |
 | AMORDEGRC  | <Badge type="info" text="Not implemented yet" /> | –                  |
 | AMORLINC   | <Badge type="info" text="Not implemented yet" /> | –                  |
-| COUPDAYBS  | <Badge type="info" text="Not implemented yet" /> | –                  |
+| COUPDAYBS  | <Badge type="tip" text="Available" /> | –                  |
-| COUPDAYS   | <Badge type="info" text="Not implemented yet" /> | –                  |
+| COUPDAYS   | <Badge type="tip" text="Available" /> | –                  |
-| COUPDAYSNC | <Badge type="info" text="Not implemented yet" /> | –                  |
+| COUPDAYSNC | <Badge type="tip" text="Available" /> | –                  |
-| COUPNCD    | <Badge type="info" text="Not implemented yet" /> | –                  |
+| COUPNCD    | <Badge type="tip" text="Available" /> | –                  |
-| COUPNUM    | <Badge type="info" text="Not implemented yet" /> | –                  |
+| COUPNUM    | <Badge type="tip" text="Available" /> | –                  |
-| COUPPCD    | <Badge type="info" text="Not implemented yet" /> | –                  |
+| COUPPCD    | <Badge type="tip" text="Available" /> | –                  |
 | CUMIPMT    | <Badge type="tip" text="Available" />          | –                  |
 | CUMPRINC   | <Badge type="tip" text="Available" />          | –                  |
 | DB         | <Badge type="tip" text="Available" />          | –                  |

docs/src/functions/financial/coupdaybs.md

@@ -7,6 +7,5 @@ lang: en-US
 # COUPDAYBS
 
 ::: warning
-🚧 This function is not yet available in IronCalc.
+🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-[Follow development here](https://github.com/ironcalc/IronCalc/labels/Functions)
 :::

docs/src/functions/financial/coupdays.md

@@ -7,6 +7,5 @@ lang: en-US
 # COUPDAYS
 
 ::: warning
-🚧 This function is not yet available in IronCalc.
+🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-[Follow development here](https://github.com/ironcalc/IronCalc/labels/Functions)
 :::

docs/src/functions/financial/coupdaysnc.md

@@ -7,6 +7,5 @@ lang: en-US
 # COUPDAYSNC
 
 ::: warning
-🚧 This function is not yet available in IronCalc.
+🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-[Follow development here](https://github.com/ironcalc/IronCalc/labels/Functions)
 :::

docs/src/functions/financial/coupncd.md

@@ -7,6 +7,5 @@ lang: en-US
 # COUPNCD
 
 ::: warning
-🚧 This function is not yet available in IronCalc.
+🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-[Follow development here](https://github.com/ironcalc/IronCalc/labels/Functions)
 :::

docs/src/functions/financial/coupnum.md

@@ -7,6 +7,5 @@ lang: en-US
 # COUPNUM
 
 ::: warning
-🚧 This function is not yet available in IronCalc.
+🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-[Follow development here](https://github.com/ironcalc/IronCalc/labels/Functions)
 :::

docs/src/functions/financial/couppcd.md

@@ -7,6 +7,5 @@ lang: en-US
 # COUPPCD
 
 ::: warning
-🚧 This function is not yet available in IronCalc.
+🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-[Follow development here](https://github.com/ironcalc/IronCalc/labels/Functions)
 :::