---
logosub: "Software"
language: "en"
title: "Conditional expressions and Guarded equations"
code: "Haskell"
---

### Conditional expressions

```haskell
signum :: Int -> Int
signum n = if n < 0 then -1 else
              if n == 0 then 0 else 1
```

And a **safetail** function, where an empty list is returned instead of an error when given an empty list.

```haskell
safetail :: [a] -> [a]
safetail xs = if length xs > 0 then tail xs else []
```

---

### Guarded equations

An alternative to conditional expressions, functions can be defined with guarded equations. 

An example of the **signum** function:

```haskell
signum :: Int -> Int
signum n | n < 0     = -1
         | n == 0    = 0
         | otherwise = 1
```

Here is **safetail** with guarded equations:

```haskell
safetail :: [a] -> [a]
safetail xs | length xs > 0 = tail xs
            | otherwise     = []
```