Add help command

Close #41

1 files changed, 3 insertions, 1 deletions

diff --git a/src/main.rs b/src/main.rs
index bc22ce2..7086d15 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -193,7 +193,9 @@ fn parse_arguments() -> Configuration {
 
 pub fn eval_math_expression(input: &str, prev_ans: Option<f64>) -> Result<f64, CalcError> {
     let input = input.trim();
-    let input = input.replace(" ", "");
+    if input == "help" {
+        return Err(CalcError::Help);
+    }
     if input.is_empty() {
         return Ok(0.);
     }