diff --git a/examples/mini_calculator.v b/examples/mini_calculator.v
index 6819529723..8a4d7fcb02 100644
--- a/examples/mini_calculator.v
+++ b/examples/mini_calculator.v
@@ -1,134 +1,135 @@
-// Q: What's this?
-// A: This is a mini "home-made" calculator. You may also regard it as a very elementary version of "interpreter".
-
-import os
-
-const (
-	numeric_char = [`0`,`1`,`2`,`3`,`4`,`5`,`6`,`7`,`8`,`9`,`.`,`e`,`E`]
-)
-
-// Convert expression to Reverse Polish Notation.
-fn expr_to_rev_pol(expr string) ?[]string {
-	if expr == '' {
-		return error('err: empty expression')
-	}
-	mut stack := []string{}
-	mut rev_pol := []string{}
-	mut pos := 0
-	for pos<expr.len {
-		mut end_pos := pos
-		for end_pos<expr.len && expr[end_pos] in numeric_char {
-			end_pos++
-		}
-		if end_pos>pos {
-			stack << expr[pos..end_pos]
-			pos = end_pos
-		}
-		else if end_pos==pos {
-			op := expr[pos].str()
-			match op {
-				'(' {
-					stack << op
-				}
-				'*', '/' {
-					for stack.len>0 && stack.last() !in ['(', '+', '-'] {
-						rev_pol << stack.last()
-						stack.delete(stack.len-1)
-					}
-					stack << op
-				}
-				'+', '-' {
-					for stack.len>0 && stack.last() != '(' {
-						rev_pol << stack.last()
-						stack.delete(stack.len-1)
-					}
-					stack << op
-				}
-				')' {
-					for stack.len>0 && stack.last() != '(' {
-						rev_pol << stack.last()
-						stack.delete(stack.len-1)
-					}
-					stack.delete(stack.len-1)
-				}
-				else {
-					return error('err: invalid character `${op}`')
-				}
-			}
-			pos++
-		}
-	}
-	for stack.len>0 {
-		top := stack.last()
-		rev_pol << top
-		stack.delete(stack.len-1)
-	}
-	return rev_pol
-}
-
-// Evaluate the result of Reverse Polish Notation.
-fn eval_rev_pol(rev_pol []string) ?f64 {
-	mut stack := []f64{}
-	for item in rev_pol {
-		if is_num_string(item) {
-			stack << item.f64()
-		}
-		else {
-			if stack.len>=2 {
-				oprand_r := stack.last()
-				stack.delete(stack.len-1)
-				oprand_l := stack.last()
-				stack.delete(stack.len-1)
-				match item {
-					'+' { stack << oprand_l+oprand_r }
-					'-' { stack << oprand_l-oprand_r }
-					'*' { stack << oprand_l*oprand_r }
-					'/' {
-						if oprand_r == 0 {
-							return error('err: divide by zero')
-						}
-						stack << oprand_l/oprand_r
-					}
-					else {}
-				}
-			}
-			else {
-				return error('err: invalid expression')
-			}
-		}
-	}
-	return stack[0]
-}
-
-fn is_num_string(str string) bool {
-	for c in str {
-		if c !in numeric_char {
-			return false
-		}
-	}
-	return true
-}
-
-
-fn main() {
-	println('Please enter the expression you want to calculate, e.g. 1e2+(3-2.5)*6/1.5 .')
-	println('Enter \'exit\' or \'EXIT\' to quit.')
-	mut expr_count := 0
-	for {
-		expr_count++
-		print('[$expr_count] ')
-		expr := os.get_line().trim_space()
-		if expr in ['exit', 'EXIT'] {
-			break
-		}
-		rev_pol := expr_to_rev_pol(expr) or {
-			eprintln(err)
-			continue
-		}
-		res := eval_rev_pol(rev_pol) or {
-			eprintln(err)
-			continue
-		}
-		println(res)
-	}
-}
+// Q: What's this?
+// A: This is a mini "home-made" calculator. You may also regard it as a very elementary version of "interpreter".
+import os
+
+const (
+	numeric_char = [`0`, `1`, `2`, `3`, `4`, `5`, `6`, `7`, `8`, `9`, `.`, `e`, `E`]
+)
+
+// Convert expression to Reverse Polish Notation.
+fn expr_to_rev_pol(expr string) ?[]string {
+	if expr == '' {
+		return error('err: empty expression')
+	}
+	mut stack := []string{}
+	mut rev_pol := []string{}
+	mut pos := 0
+	for pos < expr.len {
+		mut end_pos := pos
+		for end_pos < expr.len && expr[end_pos] in numeric_char {
+			end_pos++
+		}
+		if end_pos > pos {
+			stack << expr[pos..end_pos]
+			pos = end_pos
+		} else if end_pos == pos {
+			op := expr[pos].str()
+			match op {
+				'(' {
+					stack << op
+				}
+				'*', '/' {
+					for stack.len > 0 && stack.last() !in ['(', '+', '-'] {
+						rev_pol << stack.last()
+						stack.delete(stack.len - 1)
+					}
+					stack << op
+				}
+				'+', '-' {
+					for stack.len > 0 && stack.last() != '(' {
+						rev_pol << stack.last()
+						stack.delete(stack.len - 1)
+					}
+					stack << op
+				}
+				')' {
+					for stack.len > 0 && stack.last() != '(' {
+						rev_pol << stack.last()
+						stack.delete(stack.len - 1)
+					}
+					stack.delete(stack.len - 1)
+				}
+				else {
+					return error('err: invalid character `$op`')
+				}
+			}
+			pos++
+		}
+	}
+	for stack.len > 0 {
+		top := stack.last()
+		rev_pol << top
+		stack.delete(stack.len - 1)
+	}
+	return rev_pol
+}
+
+// Evaluate the result of Reverse Polish Notation.
+fn eval_rev_pol(rev_pol []string) ?f64 {
+	mut stack := []f64{}
+	for item in rev_pol {
+		if is_num_string(item) {
+			stack << item.f64()
+		} else {
+			if stack.len >= 2 {
+				oprand_r := stack.last()
+				stack.delete(stack.len - 1)
+				oprand_l := stack.last()
+				stack.delete(stack.len - 1)
+				match item {
+					'+' {
+						stack << oprand_l + oprand_r
+					}
+					'-' {
+						stack << oprand_l - oprand_r
+					}
+					'*' {
+						stack << oprand_l * oprand_r
+					}
+					'/' {
+						if oprand_r == 0 {
+							return error('err: divide by zero')
+						}
+						stack << oprand_l / oprand_r
+					}
+					else {}
+				}
+			} else {
+				return error('err: invalid expression')
+			}
+		}
+	}
+	return stack[0]
+}
+
+fn is_num_string(str string) bool {
+	for c in str {
+		if c !in numeric_char {
+			return false
+		}
+	}
+	return true
+}
+
+fn main() {
+	println('Please enter the expression you want to calculate, e.g. 1e2+(3-2.5)*6/1.5 .')
+	println("Enter \'exit\' or \'EXIT\' to quit.")
+	mut expr_count := 0
+	for {
+		expr_count++
+		print('[$expr_count] ')
+		expr := os.get_line().trim_space()
+		if expr in ['exit', 'EXIT'] {
+			break
+		}
+		rev_pol := expr_to_rev_pol(expr) or {
+			eprintln(err)
+			continue
+		}
+		res := eval_rev_pol(rev_pol) or {
+			eprintln(err)
+			continue
+		}
+		println(res)
+	}
+}