Add String Interpolation With Integers And Sprintf as a reasonml til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_611 TILs and counting..._
+_612 TILs and counting..._
 
 ---
 
@@ -441,6 +441,7 @@ _611 TILs and counting..._
 ### ReasonML
 
 - [Pattern Match On Exceptions](reason/pattern-match-on-exceptions.md)
+- [String Interpolation With Integers And Sprintf](reason/string-interpolation-with-integers-and-sprintf.md)
 
 ### Ruby
 

reason/string-interpolation-with-integers-and-sprintf.md

@@ -0,0 +1,27 @@
+# String Interpolation With Integers And Sprintf
+
+ReasonML's [`Printf`](https://reasonml.github.io/api/Printf.html) module
+comes with a number of functions for formatting values of various types. The
+`sprintf` function allows for string interpolation.
+
+```reason
+let red = 64;
+let green = 256;
+let blue = 128;
+let alpha = 1;
+
+let color =
+  Printf.sprintf("rbga(%i, %i, %i, %i)", red, green, blue, alpha);
+
+Js.log(color);
+```
+
+It functions the same as `fprintf` but instead of outputting the result to
+some channel, it returns a string. It enforces type checking as well -- the
+`%i` is specifically for integers, so using that with a type other than an
+integer will result in a compilation error.
+
+See the [`Printf`](https://reasonml.github.io/api/Printf.html) docs for more
+details.
+
+[source code](https://reasonml.github.io/en/try.html?reason=DYUwLgBATiAmEF4IDYAsBuAUKSBzGIAdohAEwCsyWOEARsAK4gkCMpAHNeBAIbAAOACx6ss2bgGMA9sClREmCBAAKUAJaEwAMwB0AZ37rNWgBQAiKLVw8TAUjUAaCPacvnagJRmnMWE-wgRE70TE58QjweYgBSejqyuCbSslBRQA)