1 files changed, 26 insertions, 0 deletions
diff --git a/example/math_expression/stack.go b/example/math_expression/stack.go
new file mode 100644
index 0000000..2ca8acc
--- /dev/null
+++ b/example/math_expression/stack.go
@@ -0,0 +1,26 @@
+package main
+
+// Simple lexem stack implementation.
+
+import "github.com/neonxp/unilex"
+
+type lexemStack []unilex.Lexem
+
+func (ls *lexemStack) Head() (l unilex.Lexem) {
+	if len(*ls) == 0 {
+		return unilex.Lexem{Type: unilex.LEOF}
+	}
+	return (*ls)[len(*ls)-1]
+}
+
+func (ls *lexemStack) Push(l unilex.Lexem) {
+	*ls = append(*ls, l)
+}
+
+func (ls *lexemStack) Pop() (l unilex.Lexem) {
+	if len(*ls) == 0 {
+		return unilex.Lexem{Type: unilex.LEOF}
+	}
+	*ls, l = (*ls)[:len(*ls)-1], (*ls)[len(*ls)-1]
+	return l
+}