<p>Theres is a little problem I want to solve with Haskell:
let substitute a function that change all of the wildcards in a string for one concrete parameter. The function has de signature of:</p>

<pre><code>subs :: String -&gt; String -&gt; String -&gt; String
-- example:
-- subs 'x' "x^3 + x + sin(x)" "6.2" will generate
--          "6.2^3 + 6.2 + sin(6.2)"
</code></pre>

You could use the
Text.Regex
package.
Your example might look something like this:
```
```
import Text.Regex(mkRegex, subRegex)

subs :: String -> String -> String -> String
subs wildcard input value = subRegex (mkRegex wildcard) input value
```
```