add square root function

src/main.rs

@@ -45,6 +45,7 @@ enum FunctionType {
     NaturalLog,
     Max,
     Min,
+    SquareRoot,
 }
 
 fn main() {
@@ -151,6 +152,7 @@ impl std::fmt::Display for Token {
                 FunctionType::NaturalLog => write!(f, "ln"),
                 FunctionType::Max => write!(f, "max"),
                 FunctionType::Min => write!(f, "min"),
+                FunctionType::SquareRoot => write!(f, "sqrt"),
             },
         }
     }
@@ -223,6 +225,7 @@ fn parse_buffer(buf: &str) -> Result<Token, TokenizeError> {
         "ln" => Ok(Token::Function(FunctionType::NaturalLog)),
         "max" => Ok(Token::Function(FunctionType::Max)),
         "min" => Ok(Token::Function(FunctionType::Min)),
+        "sqrt" => Ok(Token::Function(FunctionType::SquareRoot)),
         _ => {
             if let Ok(number) = buf.parse() {
                 Ok(Token::Number(number))
@@ -425,7 +428,7 @@ fn calculate(tokens: Vec<Token>) -> Result<f64, CalculateError> {
                     FunctionType::Sine => Some(n.sin()),
                     FunctionType::Cosine => Some(n.cos()),
                     FunctionType::NaturalLog => Some(n.ln()),
-
+                    FunctionType::SquareRoot => Some(n.sqrt()),
                     _ => None,
                 };
                 if let Some(n) = n {
@@ -494,6 +497,10 @@ mod tests {
             tokenize("cos"),
             Ok(vec![Token::Function(FunctionType::Cosine)])
         );
+        assert_eq!(
+            tokenize("sqrt"),
+            Ok(vec![Token::Function(FunctionType::SquareRoot)])
+        );
         assert_eq!(
             tokenize("3.14159265358979323"),
             Ok(vec![Token::Number(3.14159265358979323)])
@@ -748,5 +755,6 @@ mod tests {
         assert_eq!(compute("3sin(3)"), 3. * 3_f64.sin());
         assert_eq!(compute("(1 + 2) - (1)"), 2.);
         assert_eq!(compute("(1 + 2) - 1"), 2.);
+        assert_eq!(compute("sqrt(4)"), 2.);
     }
 }