Cleanup: convert caml_format and js_math to .res.

CHANGELOG.md

@@ -43,6 +43,7 @@
 - Fix `-nostdlib` internal compiler option. https://github.com/rescript-lang/rescript-compiler/pull/6824
 - Remove a number of ast nodes never populated by the .res parser, and resulting dead code. https://github.com/rescript-lang/rescript-compiler/pull/6830
 - Remove coercion with 2 types from internal representation. Coercion `e : t1 :> t2` was only supported in `.ml` syntax and never by the `.res` parser. https://github.com/rescript-lang/rescript-compiler/pull/6829 
+- Convert `caml_format` and `js_math` to `.res`. https://github.com/rescript-lang/rescript-compiler/pull/6834
 
 #### :nail_care: Polish
 

jscomp/others/belt_Array.res

@@ -64,10 +64,16 @@ let swapUnsafe = (xs, i, j) => {
   setUnsafe(xs, j, tmp)
 }
 
+
+@val @scope("Math") external random : unit => float = "random"
+@val @scope("Math") external floor : float => int = "floor"
+external toFloat: int => float = "%floatofint"
+
 let shuffleInPlace = xs => {
   let len = length(xs)
+  let random_int = (min, max) => floor(random() *. toFloat(max - min)) + min
   for i in 0 to len - 1 {
-    swapUnsafe(xs, i, Js_math.random_int(i, len)) /* [i,len) */
+    swapUnsafe(xs, i, random_int(i, len)) /* [i,len) */
   }
 }