From e89fd14004291f65998b8fa6b5febc2d2fdc52d6 Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Thu, 27 Jul 2023 11:53:19 -0230
Subject: addition operator

---
 calculator.go | 26 ++++++++++++++++++++++++++
 main.go       |  7 -------
 ui.go         |  2 ++
 3 files changed, 28 insertions(+), 7 deletions(-)
 create mode 100644 calculator.go

diff --git a/calculator.go b/calculator.go
new file mode 100644
index 0000000..30cc7ec
--- /dev/null
+++ b/calculator.go
@@ -0,0 +1,26 @@
+package main
+
+import "strconv"
+
+type Stack []float64
+
+type Calculator struct {
+	stack  Stack
+	buffer string
+}
+
+// add performs addition when the user inputs the '+' operator.
+func (c *Calculator) add() {
+	if len(c.stack) < 1 {
+		return
+	}
+	if con := parseConstant(c.buffer); con != nil {
+		c.stack[len(c.stack)-1] += *con
+	} else if f, err := strconv.ParseFloat(c.buffer, 64); err == nil {
+		c.stack[len(c.stack)-1] += f
+	} else if len(c.stack) > 1 {
+		c.stack[len(c.stack)-2] += c.stack[len(c.stack)-1]
+		c.stack = c.stack[:len(c.stack)-1]
+	}
+	c.buffer = ""
+}
diff --git a/main.go b/main.go
index 78f4665..85766f2 100644
--- a/main.go
+++ b/main.go
@@ -7,13 +7,6 @@ import (
 	"github.com/charmbracelet/bubbletea"
 )
 
-type Calculator struct {
-	stack  Stack
-	buffer string
-}
-
-type Stack []float64
-
 func main() {
 	if _, err := tea.NewProgram(new(UI)).Run(); err != nil {
 		fmt.Fprintf(os.Stderr, "%v", err)
diff --git a/ui.go b/ui.go
index 7472dcd..e32d20f 100644
--- a/ui.go
+++ b/ui.go
@@ -37,6 +37,8 @@ func (ui UI) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		switch msg.String() {
 		case "ctrl+c", "Q":
 			return ui, tea.Quit
+		case "+":
+			ui.calc.add()
 		case "backspace":
 			if len(ui.calc.buffer) > 0 {
 				ui.calc.buffer = ui.calc.buffer[:len(ui.calc.buffer)-1]
-- 
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