gistfile1.txt

val a = [1.0, 2.0]
val b = [1.0, 2.0]

val _ = if a = b then print "True\n"
		 else print "False\n"

---
jlouis@succubus:~$ mosml z.sml 
Moscow ML version 2.01 (January 2004)
Enter `quit();' to quit.
[opening file "z.sml"]
True
> val a = [1.0, 2.0] : real list
  val b = [1.0, 2.0] : real list
[closing file "z.sml"]
---
jlouis@succubus:~$ mlton z.sml
Error: z.sml 4.14.
  Function applied to incorrect argument.
    expects: [<equality>] * [<equality>]
    but got: [<non-equality>] * [<non-equality>]
    in: = (a, b)
compilation aborted: parseAndElaborate reported errors