number_in_month exercise

Question

I am fresh on SML and doing a homework by that. \"Write a function number_in_month that takes a list of dates and a month (i.e., an int) and returns how many dates in the li

Answer 1

You can't bind variables "that way". A binding of a variable is a declaration and thus cannot be done where an expression is expected.

In this case you have to use a let-in-end expression

fun foo x = 
  let 
    val a = 42 
  in 
    a*x
  end