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Flow-control structures: Difference between revisions
→{{header|REXX}}: added an example of raising a condition (division by zero). -- ~~~~
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===exceptions===
(See the '''signal''' statement and '''raising conditions''' below.)
===exit===
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end /*k*/
say 'sum=' sum</lang>
===raising conditions===
(REXX) conditions can be raised by causing some kind of "failure" or triggering event (such as division by zero).
A '''signal''' statement must have been issued previous to the event being triggered to enable trapping.
(Also, see the '''signal''' statement below.)
<lang rexx>...
signal on syntax
...
y=4 - 4
x=66
say x/y /*divide x by y.*/
say "yup, that's a divide by zero, by gum."
exit
syntax: say
/* We can now possibly do some repair work , but most people trap */
/* the condition, display where it happened, the REXX sourceline */
/* (the actual REXX statement), which condition was triggered, */
/* display any other pertinent REXX variables, which line in the */
/* REXX program, and then (usually) exit with some kind of error */
/* message and error code indicator. */
/* Note: the "name" of the REXX program isn't quite accurate, */
/* rather, it is the name that was invoked (called by), which may */
/* be different name than the actual program being executed. */
say '──────────────────────error!─────────────────────────'
say 'that division (above) will cause control to get here.'
parse source . . fid .
say; say 'REXX raised a SYNTAX error in program:' fid
say; say 'it occurred on line' sigl
say; say 'the REXX statement is:' /*put it on separate line.*/
say sourceline(sigl)
say; say 'which code:' condition('C') "error"
say; say 'error code:' condition('D')
say; say "Moral: don't do that."
exit 13</lang>
'''output'''
<pre>
──────────────────────error!─────────────────────────
that division (above) will cause control to get here.
REXX raised a SYNTAX error in program: D:\OOPSsay.REX
it occurred on line 6
the REXX statement is:
say x/y /*divide x by y.*/
which code: SYNTAX error
error code: Error 42.3: Arithmetic overflow; divisor must not be zero
Moral: don't do that.
</pre>
===return===
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* when a command executed returns an error return code [other than 0 (zero)].
* when a command executed indicates a failure.
(Also, see '''raising conditions''' above.)
<lang rexx>signal on error
signal on failure
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