Returns a value associated with the first true truth-valued expression in a list of paired expression arguments.
The format for the $SELECT function is:
$S[ELECT](tvexpr:expr[,...])
$SELECT() evaluates expressions from left to right.
If a truth-valued expression is TRUE (1), $SELECT() returns the corresponding expression after the colon (:) delimiter.
Once $SELECT() finds a TRUE, the function does not process any remaining arguments.
If $SELECT() finds no TRUE truth-value in its list of arguments, the function generates a run-time error.
$SELECT() does not have any effect on $TEST.
$SELECT() is one of a limited set of functions that permit an indefinite number of arguments. $SELECT() provides a means of selecting from a list of alternatives.
Generally, the last $SELECT() argument has numeric literal one (1) for a truth-value to prevent run-time errors, and to provide a "default" value.
Example:
GTM>for i=3:-1:0 write !,$select(i=1:"here",i=2:"come",i=3:"Watson") Watson come here %GTM-E-SELECTFALSE, No argument to $SELECT was true GTM>
This loop uses $SELECT() to WRITE a series of strings. Because there is no true argument on the fourth iteration, when i=0, $SELECT() produces an error.
Example:
set name=$select(sex="M":"Mr. ",sex="F":"Ms. ",1:"")_name
This example uses $SELECT() to add a prefix to the name based on a sex code held in the variable sex. Notice that the default handles the case of a missing or incorrect code.
Example:
if $select(x=+x:x,x="":0,"JANAPRJULOCT"[x:1,1:0) do THING
This uses $SELECT() to perform complex logic as the truth-valued expression argument to an IF command.
