#65 fn: IPMT, PMT and PPMT

2 files changed, 178 insertions, 0 deletions

diff --git a/calc.go b/calc.go
index e3e7c4d..3b67ef9 100644
--- a/calc.go
+++ b/calc.go
@@ -319,6 +319,7 @@ var tokenPriority = map[string]int{
 //    IMSUM
 //    IMTAN
 //    INT
+//    IPMT
 //    ISBLANK
 //    ISERR
 //    ISERROR
@@ -374,9 +375,11 @@ var tokenPriority = map[string]int{
 //    PERMUT
 //    PERMUTATIONA
 //    PI
+//    PMT
 //    POISSON.DIST
 //    POISSON
 //    POWER
+//    PPMT
 //    PRODUCT
 //    PROPER
 //    QUARTILE
@@ -7156,3 +7159,134 @@ func (fn *formulaFuncs) ENCODEURL(argsList *list.List) formulaArg {
 	token := argsList.Front().Value.(formulaArg).Value()
 	return newStringFormulaArg(strings.Replace(url.QueryEscape(token), "+", "%20", -1))
 }
+
+// Financial Functions
+
+// IPMT function calculates the interest payment, during a specific period of a
+// loan or investment that is paid in constant periodic payments, with a
+// constant interest rate. The syntax of the function is:
+//
+//    IPMT(rate,per,nper,pv,[fv],[type])
+//
+func (fn *formulaFuncs) IPMT(argsList *list.List) formulaArg {
+	return fn.ipmt("IPMT", argsList)
+}
+
+// ipmt is an implementation of the formula function IPMT and PPMT.
+func (fn *formulaFuncs) ipmt(name string, argsList *list.List) formulaArg {
+	if argsList.Len() < 4 {
+		return newErrorFormulaArg(formulaErrorVALUE, fmt.Sprintf("%s requires at least 4 arguments", name))
+	}
+	if argsList.Len() > 6 {
+		return newErrorFormulaArg(formulaErrorVALUE, fmt.Sprintf("%s allows at most 6 arguments", name))
+	}
+	rate := argsList.Front().Value.(formulaArg).ToNumber()
+	if rate.Type != ArgNumber {
+		return rate
+	}
+	per := argsList.Front().Next().Value.(formulaArg).ToNumber()
+	if per.Type != ArgNumber {
+		return per
+	}
+	nper := argsList.Front().Next().Next().Value.(formulaArg).ToNumber()
+	if nper.Type != ArgNumber {
+		return nper
+	}
+	pv := argsList.Front().Next().Next().Next().Value.(formulaArg).ToNumber()
+	if pv.Type != ArgNumber {
+		return pv
+	}
+	fv, typ := newNumberFormulaArg(0), newNumberFormulaArg(0)
+	if argsList.Len() >= 5 {
+		if fv = argsList.Front().Next().Next().Next().Next().Value.(formulaArg).ToNumber(); fv.Type != ArgNumber {
+			return fv
+		}
+	}
+	if argsList.Len() == 6 {
+		if typ = argsList.Back().Value.(formulaArg).ToNumber(); typ.Type != ArgNumber {
+			return typ
+		}
+	}
+	if typ.Number != 0 && typ.Number != 1 {
+		return newErrorFormulaArg(formulaErrorNA, formulaErrorNA)
+	}
+	if per.Number <= 0 || per.Number > nper.Number {
+		return newErrorFormulaArg(formulaErrorNA, formulaErrorNA)
+	}
+	args := list.New().Init()
+	args.PushBack(rate)
+	args.PushBack(nper)
+	args.PushBack(pv)
+	args.PushBack(fv)
+	args.PushBack(typ)
+	pmt, capital, interest, principal := fn.PMT(args), pv.Number, 0.0, 0.0
+	for i := 1; i <= int(per.Number); i++ {
+		if typ.Number != 0 && i == 1 {
+			interest = 0
+		} else {
+			interest = -capital * rate.Number
+		}
+		principal = pmt.Number - interest
+		capital += principal
+	}
+	if name == "IPMT" {
+		return newNumberFormulaArg(interest)
+	}
+	return newNumberFormulaArg(principal)
+}
+
+// PMT function calculates the constant periodic payment required to pay off
+// (or partially pay off) a loan or investment, with a constant interest
+// rate, over a specified period. The syntax of the function is:
+//
+//    PMT(rate,nper,pv,[fv],[type])
+//
+func (fn *formulaFuncs) PMT(argsList *list.List) formulaArg {
+	if argsList.Len() < 3 {
+		return newErrorFormulaArg(formulaErrorVALUE, "PMT requires at least 3 arguments")
+	}
+	if argsList.Len() > 5 {
+		return newErrorFormulaArg(formulaErrorVALUE, "PMT allows at most 5 arguments")
+	}
+	rate := argsList.Front().Value.(formulaArg).ToNumber()
+	if rate.Type != ArgNumber {
+		return rate
+	}
+	nper := argsList.Front().Next().Value.(formulaArg).ToNumber()
+	if nper.Type != ArgNumber {
+		return nper
+	}
+	pv := argsList.Front().Next().Next().Value.(formulaArg).ToNumber()
+	if pv.Type != ArgNumber {
+		return pv
+	}
+	fv, typ := newNumberFormulaArg(0), newNumberFormulaArg(0)
+	if argsList.Len() >= 4 {
+		if fv = argsList.Front().Next().Next().Next().Value.(formulaArg).ToNumber(); fv.Type != ArgNumber {
+			return fv
+		}
+	}
+	if argsList.Len() == 5 {
+		if typ = argsList.Back().Value.(formulaArg).ToNumber(); typ.Type != ArgNumber {
+			return typ
+		}
+	}
+	if typ.Number != 0 && typ.Number != 1 {
+		return newErrorFormulaArg(formulaErrorNA, formulaErrorNA)
+	}
+	if rate.Number != 0 {
+		p := (-fv.Number - pv.Number*math.Pow((1+rate.Number), nper.Number)) / (1 + rate.Number*typ.Number) / ((math.Pow((1+rate.Number), nper.Number) - 1) / rate.Number)
+		return newNumberFormulaArg(p)
+	}
+	return newNumberFormulaArg((-pv.Number - fv.Number) / nper.Number)
+}
+
+// PPMT function calculates the payment on the principal, during a specific
+// period of a loan or investment that is paid in constant periodic payments,
+// with a constant interest rate. The syntax of the function is:
+//
+//    PPMT(rate,per,nper,pv,[fv],[type])
+//
+func (fn *formulaFuncs) PPMT(argsList *list.List) formulaArg {
+	return fn.ipmt("PPMT", argsList)
+}
diff --git a/calc_test.go b/calc_test.go
index 26f8875..a3d9117 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -1132,6 +1132,16 @@ func TestCalcCellValue(t *testing.T) {
 		// Web Functions
 		// ENCODEURL
 		"=ENCODEURL(\"https://xuri.me/excelize/en/?q=Save As\")": "https%3A%2F%2Fxuri.me%2Fexcelize%2Fen%2F%3Fq%3DSave%20As",
+		// Financial Functions
+		// IPMT
+		"=IPMT(0.05/12,2,60,50000)":   "-205.26988187971995",
+		"=IPMT(0.035/4,2,8,0,5000,1)": "5.257455237829077",
+		// PMT
+		"=PMT(0,8,0,5000,1)":       "-625",
+		"=PMT(0.035/4,8,0,5000,1)": "-600.8520271804658",
+		// PPMT
+		"=PPMT(0.05/12,2,60,50000)":   "-738.2918003208238",
+		"=PPMT(0.035/4,2,8,0,5000,1)": "-606.1094824182949",
 	}
 	for formula, expected := range mathCalc {
 		f := prepareCalcData(cellData)
@@ -2019,6 +2029,40 @@ func TestCalcCellValue(t *testing.T) {
 		// Web Functions
 		// ENCODEURL
 		"=ENCODEURL()": "ENCODEURL requires 1 argument",
+		// Financial Functions
+		// IPMT
+		"=IPMT()":               "IPMT requires at least 4 arguments",
+		"=IPMT(0,0,0,0,0,0,0)":  "IPMT allows at most 6 arguments",
+		"=IPMT(0,0,0,0,0,2)":    "#N/A",
+		"=IPMT(0,-1,0,0,0,0)":   "#N/A",
+		"=IPMT(0,1,0,0,0,0)":    "#N/A",
+		"=IPMT(\"\",0,0,0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=IPMT(0,\"\",0,0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=IPMT(0,0,\"\",0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=IPMT(0,0,0,\"\",0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=IPMT(0,0,0,0,\"\",0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=IPMT(0,0,0,0,0,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		// PMT
+		"=PMT()":             "PMT requires at least 3 arguments",
+		"=PMT(0,0,0,0,0,0)":  "PMT allows at most 5 arguments",
+		"=PMT(0,0,0,0,2)":    "#N/A",
+		"=PMT(\"\",0,0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PMT(0,\"\",0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PMT(0,0,\"\",0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PMT(0,0,0,\"\",0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PMT(0,0,0,0,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		// PPMT
+		"=PPMT()":               "PPMT requires at least 4 arguments",
+		"=PPMT(0,0,0,0,0,0,0)":  "PPMT allows at most 6 arguments",
+		"=PPMT(0,0,0,0,0,2)":    "#N/A",
+		"=PPMT(0,-1,0,0,0,0)":   "#N/A",
+		"=PPMT(0,1,0,0,0,0)":    "#N/A",
+		"=PPMT(\"\",0,0,0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PPMT(0,\"\",0,0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PPMT(0,0,\"\",0,0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PPMT(0,0,0,\"\",0,0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PPMT(0,0,0,0,\"\",0)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=PPMT(0,0,0,0,0,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
 	}
 	for formula, expected := range mathCalcError {
 		f := prepareCalcData(cellData)