In the interests of nitpicking,
I'm not sure how interesting nitpicking is ;), but if we're going that route ...
implemented using a for loop in C, which does operate in a defined and documented order.
It uses the for loop to pick values off the stack, and return qualifying results to the stack, which then get return to the caller in the stacked order.
Which is no different to what grep does. Albeit that the iteration is split between pp_grepwhile() in pphot.c and pp_grepstart() in pp_ctrl.c.
In the end, it is the fact that the list out is derived -- in sequence -- from the list in, that defines the ordering in both cases.
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.