Introspection: Difference between revisions

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=={{header|REXX}}==
=={{header|REXX}}==
Test to see if the version is at least version 4.
Test to see if the version is at least version 4.
<lang rexx> /*output from parse version (almost all REXX versions) */
<lang rexx> /*output from parse version (almost all REXX versions) */
/* theREXXinterpreterName level mm Mon yyyy */
/* theREXXinterpreterName level mm Mon yyyy */

parse version . level .
parse version . level .
if level<4 then exit</lang>
if level<4 then exit</lang>
Test to see if the version is at least version 4, another example.
Test to see if the version is at least version 4, another example.
<lang rexx>parse version x 1 whatLang level mm mon yyyy .
<lang rexx>parse version x 1 whatLang level dd mon yyyy .
if level<4 then do
if level<4 then do
say
say
say 'version' level "is too old!"
say 'version' level "is too old!"
say x /*this displays everything.*/
say x /*this displays everything.*/
exit /*or maybe: EXIT 13 */
exit /*or maybe: EXIT 13 */
end</lang>
end</lang>
Test to see if the REXX variable "bloop" exists, version 1.
Test to see if the REXX variable "bloop" exists, version 1.
<lang rexx>if symbol('bloop')=='VAR' then say 'the "bloop" variable exists.'</lang>
<lang rexx>if symbol('bloop')=='VAR' then say 'the "bloop" variable exists.'</lang>
Test to see if the REXX variable "bloop" exists, version 2.
Test to see if the REXX variable "bloop" exists, version 2.
<lang rexx>if symbol('bloop')=='VAR' then say 'the "bloop" variable exists.'
<lang rexx>if symbol('bloop')=='VAR' then say 'the "bloop" variable exists.'
else say 'the "bloop" variable doesn''t exist.'</lang>
else say 'the "bloop" variable doesn''t exist.'</lang>
Programming note: &nbsp; note the use of the double apostrophe &nbsp; (<big>''' ' ' '''</big>) &nbsp; which is within a quoted string (with apostrophes) &nbsp; [in the above and below REXX programming examples].
Programming note: &nbsp; note the use of the double apostrophe &nbsp; (<big>''' ' ' '''</big>) &nbsp; which is within a quoted string (with apostrophes) &nbsp; [in the above and below REXX programming examples].


<br>Another test to see if the REXX variable "bloop" exists.
<br>Another test to see if the REXX variable "bloop" exists.
<lang rexx>bloop=47
<lang rexx>bloop=47
if symbol('bloop')=='VAR' then say 'the "bloop" variable exists.'
if symbol('bloop')=='VAR' then say 'the "bloop" variable exists.'
else say 'the "bloop" variable doesn''t exist.'</lang>
else say 'the "bloop" variable doesn''t exist.'</lang>
In REXX, the ABS function is a built-in function (BIF).
In REXX, the ABS function is a built-in function (BIF).
<lang rexx>bloop=47
<lang rexx>bloop=47
g=abs(bloop)</lang>
g=abs(bloop)</lang>
However, most REXX interpretors will allow this type of test:
However, most REXX interpreters will allow this type of test:
<lang rexx>if testxyz() then say 'function XYZ not found.'
<lang rexx>if testxyz() then say 'function XYZ not found.'
else say 'function XYZ was found.'
else say 'function XYZ was found.'
exit
exit
/*──────────────────────────────────────────────────────────────────────────────────────*/

testxyz: signal on syntax
testxyz: signal on syntax
call XYZ
call XYZ
return 0
return 0
/*──────────────────────────────────────────────────────────────────────────────────────*/

syntax: return 1</lang>
syntax: return 1</lang>


=={{header|Ruby}}==
=={{header|Ruby}}==
Retrieved from "https://rosettacode.org/wiki/Introspection"