Question

I am strugging a bit to implement a nested if else expressions in SML. Can anyone highlight its syntax. Suppose there are three conditions C1, C2, C3 I need equivalent of following in C code.

if (C1) { 
    return true;
}
else {
    if(C2) {
        return true;
    }
    else {
         if (C3) {
             return true;
         }
         else {
             return false;
         }
    }
}

I tried the following, but its treated as “if, else if, and else” cases

if C1 then true
else if C2 then true
else if C3 then true
else false

Answer 1

You’re correct. Two code fragments are equivalent.

With a bit of indentation, your SML example looks more like using nested if/else:

if C1 then true
else
    if C2 then true
    else
        if C3 then true
        else false

You could also use parentheses so that SML example looks almost the same as C example but it isn’t necessary.

Of course, the most idiomatic way in SML is to write

C1 orelse C2 orelse C3

You could use the same trick for your C code. Remember that returning true/false in if/else blocks is code smell.