standardssml

Difference between chr and Char.chr in Standard ML

My program:

val a = chr 65 : char
val b = Char.chr 65: char
val _ = print (Char.toString a)
val _ = print (Char.toString b)

Output:

AA

Lines 1 and 2 show that both chr and Char.chr work.

Is there a difference between the two? And which one is conformant to Standard ML 97 and why?

Solution

  • They are the same function. Char.chr is simply available at the top-level of any SML program unqualified by its module name.

    Should you bind the name chr to another value at the top-level of your program, the original would still be available via the fully-qualified name Char.chr.

    Further reading