From 6817d5861986084f55785842b07639f7aeaacf0a Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Sat, 4 Oct 2025 13:56:56 -0400
Subject: accept e-notation

---
 calc.go | 10 +++-------
 op.go   |  9 ++++++---
 ui.go   | 24 +++++++++++++++++++++---
 3 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/calc.go b/calc.go
index 67794aa..1e0e598 100644
--- a/calc.go
+++ b/calc.go
@@ -61,17 +61,13 @@ func (c *Calculator) negate() {
 	}
 }
 
-// performOp performs the specified arithmetic operation.
-func (c *Calculator) performOperation(operator byte) {
-	fn, err := parseOperator(operator)
-	if err != nil {
-		return
-	}
+// operate performs a binary arithmetic operation on the stored values.
+func (c *Calculator) operate(op Op) {
 	lhs, rhs, err := c.operands()
 	if err != nil {
 		return
 	}
-	c.stack.push(fn(lhs, rhs))
+	c.stack.push(op(lhs, rhs))
 	c.buf = ""
 }
 
diff --git a/op.go b/op.go
index 6ccc6a8..3a193b6 100644
--- a/op.go
+++ b/op.go
@@ -5,9 +5,12 @@ import (
 	"math"
 )
 
-// parseOperator returns a closure that performs the specified arithmetic operation,
-// or OpError if op is not a valid operator.
-func parseOperator(op byte) (func(lhs float64, rhs float64) float64, error) {
+// Op is a binary operator.
+type Op func(lhs, rhs float64) float64
+
+// parseOp parses a binary operator, returning a function that performs the operation, or
+// OpError if op is not a valid operator.
+func parseOperator(op byte) (Op, error) {
 	switch op {
 	case '+':
 		return func(lhs, rhs float64) float64 { return lhs + rhs }, nil
diff --git a/ui.go b/ui.go
index cea51e7..02f2bb1 100644
--- a/ui.go
+++ b/ui.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/charmbracelet/bubbletea"
 )
@@ -52,9 +53,22 @@ func (ui UI) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			ui.calc.angleMode = !ui.calc.angleMode
 		case "N":
 			ui.calc.negate()
-		case "+", "-", "*", "/", "%", "^":
-			operator := msg.String()[0]
-			ui.calc.performOperation(operator)
+		case "+", "-":
+			if isENotation(ui.calc.buf) {
+				ui.calc.buf += msg.String()
+			} else {
+				op, err := parseOperator(msg.String()[0])
+				if err != nil {
+					panic(err)
+				}
+				ui.calc.operate(op)
+			}
+		case "*", "/", "%", "^":
+			op, err := parseOperator(msg.String()[0])
+			if err != nil {
+				panic(err)
+			}
+			ui.calc.operate(op)
 		case "backspace":
 			if len(ui.calc.buf) > 0 {
 				ui.calc.buf = ui.calc.buf[:len(ui.calc.buf)-1]
@@ -75,6 +89,10 @@ func (ui UI) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	return ui, nil
 }
 
+func isENotation(s string) bool {
+	return strings.ContainsRune(s, 'e')
+}
+
 func (ui UI) View() string {
 	s := padding(ui)
 
-- 
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