On 06.09.2020 18:42, Mike Cowlishaw wrote:
>
>
> On 05.09.2020 21:48, Mike Cowlishaw wrote:
>> Rony, this was added to NetRexx back in the 1990s.
>
> yes, this also meant that translating NetRexx to Java would be
> straight-forward, but NetRexx
> broke compatibility with Rexx in that respect (which has not been a
> problem).
>
>
>
> I don't follow .. the shortcircuit in NetRexx uses a comma in a place that
> was not
> allowed/possible in Rexx:
>
> Multiple expressions, separated by commas, can be given on the *if
> *clause, which then has the
> syntax:
>
> *if */expression/[, /expression/]... [;]
>
> In this case, the expressions are evaluated in turn from left to right,
> and if the result of
> any evaluation is 1 then the test has succeeded and the instruction
> following the associated
> *then *clause is executed. If all the expressions evaluate to 0 and an
> *else *was given then
> the instruction after the *else *is executed.
>
> Note that once an expression evaluation has resulted in 1, no further
> expressions in the
> clause are evaluated. So, for example, in:
>
> -- assume 'name' is a string
> if name=null, name='' then say 'Empty'
>
> then if name does not refer to an object it will compare equal to null
> and the *say
> *instruction will be executed without evaluating the second expression in
> the *if *clause.
>
> How does that break compatibility with Rexx?
>
The code does not run on Rexx, here an example feeding your example to Regina:
G:\test\regina\work>regina -v regina: REXX-Regina_3.9.3(MT) 5.00 5 Oct 2019
(32 bit)
G:\test\regina\work>type testshortcirc.rex -- assume 'name' is a string if
name=null, name=''
then say 'Empty' G:\test\regina\work>regina testshortcirc.rex Error 18
running
"G:\test\regina\work\testshortcirc.rex", line 2: THEN expected Error 18.1:
IF keyword on line 2
requires matching THEN clause; found ", "
---rony
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