feat: add comment support to saccharine language

Add '#' comment syntax that works like Python comments.
Comments can take up a whole line or appear at the end of a line.
All characters after '#' until the next newline or EOF are ignored.

Closes #24

pkg/saccharine/token/parse.go

@@ -77,6 +77,23 @@ func getToken(i *iterator.Iterator[rune]) (*Token, error) {
 		}
 	case letter == ';':
 		return NewHardBreak(index), nil
+	case letter == '#':
+		// Skip everything until the next newline or EOF
+		for {
+			if i.Done() {
+				break
+			}
+			r, err := i.Next()
+			if err != nil {
+				return nil, trace.Wrap(err, "error while parsing comment")
+			}
+			if r == '\n' {
+				// Put the newline back so it can be processed as a soft break
+				i.Back()
+				break
+			}
+		}
+		return nil, nil
 	case unicode.IsSpace(letter):
 		return nil, nil
 	case isVariable(letter):

tests/comments.expected

@@ -0,0 +1 @@
+VALUE

tests/comments.test

@@ -0,0 +1,15 @@
+# This is a full-line comment at the start
+# The following defines the identity function
+identity := \x.x # This is an end-of-line comment
+
+# Define a simple function that applies a function twice
+twice := \f.\x.(f (f x))
+
+# Test that comments don't interfere with expressions
+result := (twice identity VALUE) # Should just return VALUE
+
+# Multiple comments in a row
+# can appear anywhere
+# without breaking the code
+
+result # Final comment at the end