How do I count booleans?

Boolean can be counted by using the SWITCH function

Example:

boolean b[3]; 
b[1] = true;  b[2] = false;  b[3] = true;
integer a;    
a = lsum(i = 1 to 3, b[i]);

Error message: Syntax error: Not allowed to use a Boolean expression

Solution:

a = lsum(i=1 to 3,switch(b[i] ? 1 else 0));