In message <pURRj.3093$PM5.3083@[EMAIL PROTECTED]
>, Duke Normandin
<dukeofperl@[EMAIL PROTECTED]
> writes
>set i=1,j=2,k=3
>if i<j&k>j write "yes",!
>
>i _is_ less than j AND k _is_ greater than j
>
>so why is _yes_ NOT printed?
>
>The logical operator & tells me that both relational expressions must
>be true in order for the _yes_ to be printed. That's exactly what it is,
>so what am I missing? TIA......
Left to right operator precedence.
i<j is true so evaluated to 1
1&k is true so evaluates to 1
1>j is false so yes is not printed.
to obtain the correct result the conditions should be in parentheses
if (i<j)&(j>j) write yes.
However an alternate would be
if i<j,k>j write yes
This is possibly preferred in that the command is broken into two
commands, and the second one only executed if the first one is true.
The reason for the preference is performance. The second condition is
only evaluated if the first is true, so by putting the least likely
condition first one can optimise the code.
Optimisation should only be done when the code retains clarity, and when
it is executed sufficiently often to justify the work.
--
Philip Gage
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