Undefined values: Difference between revisions

<lang rexx>/*REXX program test if a (REXX) variable is defined or not defined. */

tlaloc = "rain god of the Aztecs." /*assign a value to the Aztec rain god.*/

/*check if the rain god is defined. */

y= 'tlaloc'

if symbol(y)=="VAR" then say y ' is defined.'

else say y "isn't defined."

/*check if the fire god is defined. */

y= 'xiuhtecuhtli' /*assign a value to the Aztec file god.*/

if symbol(y)=="VAR" then say y ' is defined.'

else say y "isn't defined."

drop tlaloc /*un─define the TLALOC REXX variable.*/

/*check if the rain god is defined. */

y= 'tlaloc'

if symbol(y)=="VAR" then say y ' is defined.'

else say y "isn't defined."

/*stick a fork in it, we're all done. */</lang>

<pre>

tlaloc is defined.

xiuhtecuhtli isn't defined.

tlaloc isn't defined.