Exceptions/Catch an exception thrown in a nested call: Difference between revisions

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=={{header|REXX}}==
=={{header|REXX}}==
While the REXX language doesn't have a ''throw'' capability ''pe se'',
While the REXX language doesn't have a ''throw'' capability ''pe se'', it does have the ability to catch exceptions (by label).
⚫
<br>This type of exception handling (in REXX) has its limitation &nbsp;
it does have the ability to catch exceptions (by label).
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(the label is known global to the program, not external subroutines).
⚫
<br>This type of exception handling (in REXX) has its limitation
⚫
(the label is local to the program, not external subroutines).
<lang rexx>/*REXX program to create two exceptions & demonstrate how to handle them*/
<lang rexx>/*REXX program to create two exceptions & demonstrate how to handle them*/
call foo /*invoke the FOO function. */
call foo /*invoke the FOO function. */
say 'mainline program is done.' /*indicate that Elroy was here. */
say 'mainline program is done.' /*indicate that Elroy was here. */
exit /*stick a fork in it, we're done.*/
exit /*stick a fork in it, we're done.*/

/*──────────────────────────────────FOO function────────────────────────*/
/*──────────────────────────────────FOO function────────────────────────*/
foo: call bar; call bar /*invoke BAR function twice. */
foo: call bar; call bar /*invoke BAR function twice. */
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U0: say 'exception U0 caught in FOO' /*handle the U0 exception. */
U0: say 'exception U0 caught in FOO' /*handle the U0 exception. */
return -2 /*return to the invoker. */
return -2 /*return to the invoker. */

/*──────────────────────────────────BAR function────────────────────────*/
/*──────────────────────────────────BAR function────────────────────────*/
bar: call baz /*have BAR invoke BAZ function. */
bar: call baz /*have BAR invoke BAZ function. */
return 0 /*return a zero to invoker. */
return 0 /*return a zero to invoker. */

/*──────────────────────────────────BAZ function────────────────────────*/
/*──────────────────────────────────BAZ function────────────────────────*/
baz: if symbol('BAZ#')=='LIT' then baz#=0 /*initialize BAZ invocation#*/
baz: if symbol('BAZ#')=='LIT' then baz#=0 /*initialize BAZ invocation#*/
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if baz#==1 then signal U0 /*if first invocation, raise U0 */
if baz#==1 then signal U0 /*if first invocation, raise U0 */
if baz#==2 then signal U1 /* " second " " U1 */
if baz#==2 then signal U1 /* " second " " U1 */
return 0 /*return a zero to invoker. */
return 0 /*return a 0 (zero) to invoker.*/
U0: return -1 /*handle exception if not caught.*/
/* [↓] this U0 sub is ignored.*/
U1: return -1 /* " " " " " */</lang>
U0: return -1 /*handle exception if not caught.*/
U1: return -1 /* " " " " " */</lang>
{{out}}
{{out}}
<pre>
<pre>
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