feat: rename ComputeNPV/IRR to NPV/IRR for consistency

README.md

@@ -111,7 +111,7 @@ c.Restore(state)
 | Arithmetic   | `Add`, `Sub`, `Mul`, `Div`, `YPowX`                                                            |
 | TVM store    | `SetN`, `SetI`, `SetPV`, `SetPMT`, `SetFV`                                                     |
 | TVM solve    | `SolveN`, `SolveI`, `SolvePV`, `SolvePMT`, `SolveFV`                                           |
-| Cash flow    | `ComputeNPV`, `ComputeIRR`                                                                     |
+| Cash flow    | `NPV`, `IRR`                                                                                   |
 | Amortization | `Amortize`                                                                                     |
 | Bonds        | `BondPrice`, `BondYield`                                                                       |
 | Depreciation | `DepreciationSL`, `DepreciationSOYD`, `DepreciationDB`                                         |
@@ -144,6 +144,7 @@ c.Program, c.PgmLen, c.PgmPC                 // program storage
 
 ```bash
 go run examples/mortgage/main.go    # $300K mortgage payment
+go run examples/solve-tvm/main.go   # unified TVM solver
 go run examples/npv/main.go         # NPV + IRR
 go run examples/fv/main.go          # future value
 go run examples/stats/main.go       # statistics (engine)

calculator.go

@@ -189,9 +189,9 @@ func (c *CalcService) solveTVM(op string) {
 func (c *CalcService) unprefixed(op string, arg float64) {
 	switch op {
 	case "NPV":
-		c.e.ComputeNPV()
+		c.e.NPV()
 	case "IRR":
-		c.e.ComputeIRR()
+		c.e.IRR()
 	case "PRICE":
 		c.e.BondPrice()
 	case "YTM":
@@ -301,9 +301,9 @@ func (c *CalcService) fPrefixed(op string, arg float64, argS string) {
 	case "INT":
 		c.e.X = c.e.AmortInt
 	case "NPV":
-		c.e.ComputeNPV()
+		c.e.NPV()
 	case "IRR":
-		c.e.ComputeIRR()
+		c.e.IRR()
 	case "PRICE":
 		c.e.BondPrice()
 	case "YTM":

engine/engine_test.go

@@ -310,7 +310,7 @@ func TestNPVAndIRR(t *testing.T) {
 	e.FinCFj[2] = 70
 	e.FinCfCnt = 3
 	e.X = 10
-	e.ComputeNPV()
+	e.NPV()
 	if math.Abs(e.X-47.63) > 0.1 {
 		t.Fatalf("NPV: want ~47.63, got %v", e.X)
 	}
@@ -320,7 +320,7 @@ func TestNPVAndIRR(t *testing.T) {
 	e.FinCFj[1] = 60
 	e.FinCfCnt = 2
 	e.Flags.StackLift = true
-	e.ComputeIRR()
+	e.IRR()
 	if math.Abs(e.X-13.07) > 0.5 {
 		t.Fatalf("IRR: want ~13.07, got %v", e.X)
 	}

engine/example_test.go

@@ -45,7 +45,7 @@ func Example_npv() {
 	c.FinCfCnt = 4
 	c.X = 10
 	c.Flags.StackLift = true
-	c.ComputeNPV()
+	c.NPV()
 
 	fmt.Printf("NPV: $%.2f\n", c.X)
 	// Output: NPV: $38877.13
@@ -60,7 +60,7 @@ func Example_irr() {
 	c.FinCFj[2] = 30000
 	c.FinCfCnt = 3
 	c.Flags.StackLift = true
-	c.ComputeIRR()
+	c.IRR()
 
 	fmt.Printf("IRR: %.2f%%\n", c.X)
 	// Output: IRR: 10.13%
@@ -174,7 +174,7 @@ func TestExamples(t *testing.T) {
 		c.FinCfCnt = 4
 		c.X = 10
 		c.Flags.StackLift = true
-		c.ComputeNPV()
+		c.NPV()
 		if math.Abs(c.X-38877.13) > 1 {
 			t.Fatalf("NPV: want ~38877, got %v", c.X)
 		}
@@ -188,7 +188,7 @@ func TestExamples(t *testing.T) {
 		c.FinCFj[2] = 30000
 		c.FinCfCnt = 3
 		c.Flags.StackLift = true
-		c.ComputeIRR()
+		c.IRR()
 		if math.Abs(c.X-10.13) > 0.5 {
 			t.Fatalf("IRR: want ~10.13, got %v", c.X)
 		}

engine/financial.go

@@ -99,12 +99,12 @@ func (e *Engine) cashflows() []float64 {
 	return cfs
 }
 
-func (e *Engine) ComputeNPV() {
+func (e *Engine) NPV() {
 	e.X = clamp(NPV(e.X/100, e.cashflows()...))
 	e.Flags.StackLift = true
 }
 
-func (e *Engine) ComputeIRR() {
+func (e *Engine) IRR() {
 	r, _ := IRR(e.cashflows()...)
 	e.result(r * 100)
 }

engine/regress_test.go

@@ -31,7 +31,7 @@ func TestRegressNPV_ConsumesRate(t *testing.T) {
 	e.Y = 2
 	e.X = 10
 	e.Flags.StackLift = true
-	e.ComputeNPV()
+	e.NPV()
 	if math.Abs(e.X-47.63) > 0.1 {
 		t.Fatalf("X=%v", e.X)
 	}

examples/solve-tvm/main.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/shanehull/dozen/engine"
+)
+
+func main() {
+	// $300K mortgage, 30 years, monthly payment of $1,798.65.
+	// What's the APR? Pass NaN for the unknown.
+	i, _ := engine.SolveTVM(360, math.NaN(), 300000, -1798.65, 0, engine.End)
+	fmt.Printf("Rate: %.2f%% APR\n", i*12*100)
+
+	// How many months to pay off with $2,000/mo?
+	n, _ := engine.SolveTVM(math.NaN(), 0.06/12, 300000, -2000, 0, engine.End)
+	fmt.Printf("Term: %.0f months at $2,000/mo\n", n)
+
+	// What loan can I afford at $1,500/mo over 30 years?
+	pv, _ := engine.SolveTVM(360, 0.06/12, math.NaN(), -1500, 0, engine.End)
+	fmt.Printf("Loan: $%.0f\n", pv)
+}