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

Your problem is endless recursion. Compiler can't get out of it because independ of result if..then..else you're running your function again Try this:

fun number_in_month (dates: (int*int*int) list,month:int) = 
    if null dates
    then 0
    else if ((#2 (hd dates)) = month)
    then val flag=1 flag+number_in_month(tl dates, month) 
    else number_in_month((tl dates),month)