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Id: 124548
Status: open
Priority: 0/
Queue: perl6

Owner: Nobody
Requestors: davidnmfarrell [at] gmail.com
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This ticket is about two currently skipped tests in S03-operators/flip-flop.t. The tests in question check how often the left hand side (lhs) and right hand side (rhs) are evaluated against $_ when using the operators 'ff' and 'fff', respectively: # make sure {lhs,rhs} isn't evaluated when state is {true,false} #?rakudo skip 'dubious scoping? RT #124548' { # keep track of # of times lhs and rhs are EVAL'd by adding # a state var to both sides. sub ff_eval($code, $lhs, $rhs, @a) { my $lhs_run = 0; my $rhs_run = 0; for @a { $code.({$lhs_run++; ?$lhs}, {$rhs_run++; ?$rhs}); } return [$lhs_run, $rhs_run]; } is-deeply ff_eval({@_[0]() ff @_[1]()}, /B/, /B/, <A B A B A>), [5, 2], "count lhs & rhs evals for ff"; is-deeply ff_eval({@_[0]() fff @_[1]()}, /B/, /B/, <A B A B A>), [3, 2], "count lhs & rhs evals for fff"; } Currently, the second test passes, but the first fails because the sub returns [5, 5]. So lhs and rhs are evaluated 5 times both. After looking at the speculations (S03), the docs (doc/Language/operators.pod) and the implementation (sub flipflop src/Perl6/Actions.nqp) I'm under the impression that [5, 5] is a sensible answer. * S03 states: "The two sides of a flipflop are evaluated as smartmatches against the current value of the topic stored in $_.". That's in line with current behaviour. * http://doc.perl6.org/routine/ff states: "Compares both arguments to $_ (that is, $_ ~~ $a and $_ ~~ $b)." That's also in line with current behaviour. * src/Perl6/Actions.nqp: There is the following explicit comment in sub flipflop: # Evaluate LHS and RHS. Note that in one-only mode, we use # the state bit to decide which side to evaluate. All in all, I think the first tests is wrong and should be changed. (I guess, no adjustments in 6.c-errata are necessary since the test was skipped there.)


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