http://code.kx.com/wiki/Reference/DollarSign#cond
/ what is the difference between using $ (conditional) and if?
/ does if evaluate the expression but not “return” it?
q)$[0b;true;false]
`false
q)if[0b;true;false] / why isn’t `false output?
q)
q)($[0b;true;false])~(if[0b;true;false])
0b
q)($[0b;true;false])~($[0b;true;false])
1b
Hi,
Yes you are correct, an ‘if’ statement will execute all following statements if the check is true BUT will not return anything.
The $ conditional is an if-else statement which does have a return value.
q)if[1b;a:10;b:20;c:30]
q)a
10
q)b
20
q)c
30
$[true;do this;else do this]
or
$[if cond1 true;do this;else check cond 2;if true do this;else do this]
q)$[1b;“yes”;“no”]
“yes”
q)
q)$[0b;“yes”;“no”]
“no”
q)$[0>1;“cond 1 true”;0<1;“cond 2 true”;“cond 2 false”]
“cond 2 true”
Regards,
Jason
Jason Fealy | Kx Engineer | Kx | +1 (718) 340-9791 | jfealy@kx.com
‘if’ conditionally evaluates all blocks after the condition and returns nothing
http://code.kx.com/wiki/Reference/if
$[;;…] is used for lazy evaluation of an if/elsif/elsif/…/else statement and returns the last evaluated block.
http://code.kx.com/wiki/Reference/DollarSign#cond