From 2ce8cc7a7e9862f8e8177387a9cf2f1dc5c69bc0 Mon Sep 17 00:00:00 2001
From: "T.v.Dein" <git@daemon.de>
Date: Tue, 7 Nov 2023 14:18:46 +0100
Subject: [PATCH] add comments support (#7)

---
 Makefile     |  4 +--
 README.md    |  1 +
 calc.go      |  5 +++-
 calc_test.go | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 rpn.pod      | 10 +++++++
 5 files changed, 90 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index ac90935..848fb3f 100644
--- a/Makefile
+++ b/Makefile
@@ -57,8 +57,8 @@ test:
 	go test -v ./...
 
 singletest:
-	@echo "Call like this: ''make singletest TEST=TestPrepareColumns MOD=lib"
-	go test -run $(TEST) github.com/tlinden/rpn/$(MOD)
+	@echo "Call like this: ''make singletest TEST=TestPrepareColumns"
+	go test -run $(TEST)
 
 cover-report:
 	go test ./... -cover -coverprofile=coverage.out
diff --git a/README.md b/README.md
index 7082e77..0770bc7 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,7 @@ Features:
 - provides interactive repl
 - completion
 - history
+- comments (comment character is `#`)
 
 
 ## Working principle
diff --git a/calc.go b/calc.go
index d9f6353..fbec70a 100644
--- a/calc.go
+++ b/calc.go
@@ -38,6 +38,7 @@ type Calc struct {
 	completer    readline.AutoCompleter
 	interpreter  *Interpreter
 	Space        *regexp.Regexp
+	Comment      *regexp.Regexp
 	Constants    []string
 	LuaFunctions []string
 
@@ -133,6 +134,7 @@ func NewCalc() *Calc {
 	)
 
 	c.Space = regexp.MustCompile(`\s+`)
+	c.Comment = regexp.MustCompile(`#.*`) // ignore everything after #
 
 	// pre-calculate mode switching arrays
 	c.Constants = strings.Split(Constants, " ")
@@ -189,7 +191,8 @@ func (c *Calc) Prompt() string {
 
 // the actual work horse, evaluate a line of calc command[s]
 func (c *Calc) Eval(line string) {
-	line = strings.TrimSpace(line)
+	// remove surrounding whitespace and comments, if any
+	line = strings.TrimSpace(c.Comment.ReplaceAllString(line, ""))
 
 	if line == "" {
 		return
diff --git a/calc_test.go b/calc_test.go
index 3ad864a..b8f48c3 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -22,6 +22,79 @@ import (
 	"testing"
 )
 
+func TestCommentsAndWhitespace(t *testing.T) {
+	calc := NewCalc()
+
+	var tests = []struct {
+		name string
+		cmd  []string
+		exp  float64 // last element of the stack
+	}{
+		{
+			name: "whitespace prefix",
+			cmd:  []string{"  5"},
+			exp:  5.0,
+		},
+		{
+			name: "whitespace postfix",
+			cmd:  []string{"5  "},
+			exp:  5.0,
+		},
+		{
+			name: "whitespace both",
+			cmd:  []string{"  5   "},
+			exp:  5.0,
+		},
+		{
+			name: "comment line w/ spaces",
+			cmd:  []string{"5", "   #   19"},
+			exp:  5.0,
+		},
+		{
+			name: "comment line w/o spaces",
+			cmd:  []string{"5", `#19`},
+			exp:  5.0,
+		},
+		{
+			name: "inline comment w/ spaces",
+			cmd:  []string{"5   #   19"},
+			exp:  5.0,
+		},
+		{
+			name: "inline comment w/o spaces",
+			cmd:  []string{"5#19"},
+			exp:  5.0,
+		},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("%s .(expect %.2f)",
+			tt.name, tt.exp)
+
+		t.Run(testname, func(t *testing.T) {
+			for _, line := range tt.cmd {
+				calc.Eval(line)
+			}
+			got := calc.stack.Last()
+
+			if len(got) > 0 {
+				if got[0] != tt.exp {
+					t.Errorf("parsing failed:\n+++  got: %f\n--- want: %f",
+						got, tt.exp)
+				}
+			}
+
+			if calc.stack.Len() != 1 {
+				t.Errorf("invalid stack size:\n+++  got: %d\n--- want: 1",
+					calc.stack.Len())
+			}
+
+		})
+
+		calc.stack.Clear()
+	}
+}
+
 func TestCalc(t *testing.T) {
 	calc := NewCalc()
 
diff --git a/rpn.pod b/rpn.pod
index c965396..117828d 100644
--- a/rpn.pod
+++ b/rpn.pod
@@ -213,6 +213,16 @@ Search through history.
 
 =back
 
+=head1 COMMENTS
+
+Lines starting with  C<#> are being ignored as comments.  You can also
+append comments to rpn input, e.g.:
+
+   # a comment
+   123   # another comment
+
+In this case only 123 will be added to the stack.
+
 =head1 EXTENDING RPN USING LUA
 
 You can use a lua script with lua functions to extend the