I had a look at the remaining places mentioning --heuristic, --evaluator, and --landmarks. Most of them are about supporting the old syntax, or documenting that the old syntax is now deprecated:


docs/search-plugin-syntax.md:      Documentation warning about deprecation
src/search/plugins/doc_printer.cc: Documentation warning about deprecation
CHANGES.md:                        Documentation warning about deprecation
                                   + one older change log entry from the time
                                     when the option still existed
src/search/command_line.cc:        rewriting old syntax into let expressions
driver/portfolio_runner.py:        Support for the legacy arguments

Other than that, I only found 3 remaining cases:

misc/tests/configs.py:
    The bjolp test config still uses the old "--evaluator".
    We can just rewrite it in the new style.

driver/arguments.py:
    One of the example configurations in the driver shows a predefinition
    but marked as "(old style)" with the new style above.
    We could just remove it.

docs/search-plugin-syntax.md:
    This contains an example that is more complex to rewrite:
        --if-unit-cost --evaluator "h1=ff()" --evaluator "h2=blind()" \
        --if-non-unit-cost --evaluator "h1=cea()" --evaluator "h2=lmcut()" \
        --always --search "eager_greedy([h1, h2])"

    One option is
        --if-unit-cost --search \
            "let(h1, ff(), let(h2, blind(), eager_greedy([h1, h2])))" \
        --if-non-unit-cost --search \
            "let(h1, cea(), let(h2, lmcut(), eager_greedy([h1, h2])))"
    but it duplicates the part that previously was written as --always.

Some of the usages have been removed as part of issue1190.

BTW, from your comment perhaps we're also unclear about what this issue is about? The goal of this issue is not to to stop supporting the old syntax but to stop using it ourselves internally.

That is something I am still much in favour of. I understand the concern for end users, but I think it is really better if we ourselves use the syntax that matches what goes on under the hood.

Good for a meeting, yes.

First comment for now: I see what you mean. I think it makes little sense to allow assignment for evaluators and landmark factories, but nothing else. So the syntax as it currently stands is not something I'd like to keep indefinitely.

But at a glance I see nothing wrong with something which is like our current syntax but without the words "--evaluator" etc., as in:

h1=ff()
h2=lmcount()
eager_greedy([h1,h2])

or whatever, with support for all plugin types, not just evaluators and landmark factories.

I also don't think it's that much more difficult to write this as

let(h1,ff(),
let(h2,lmcount(),
eager_greedy([h1,h2])
))

but I guess it looks foreign without exposure to functional programming.

Couldn't we just keep the --evaluator and --landmarks syntax indefinitely? I much prefer it over the let statements, especially if there are multiple predefinitions which leads to deeply nested brackets. This could be a topic for a Fast Downward meeting, I guess.

We currently still use the deprecated syntax --heuristic and --evaluator in some places, including ones that end up on the documentation. These should be removed in favour of the let syntax, especially if we want to remove support for the old syntax eventually. These are the hits (outside of experiments) in the current codebase for --heuristic, --evaluator and --landmarks:

--evaluator:

./misc/tests/configs.py
./driver/portfolio_runner.py
./driver/arguments.py
./src/search/search_algorithms/plugin_eager_greedy.cc
./src/search/search_algorithms/iterated_search.cc
./src/search/search_algorithms/plugin_lazy_greedy.cc
./src/search/search_algorithms/plugin_astar.cc
./src/search/search_algorithms/plugin_lazy_wastar.cc
./src/search/command_line.cc
./src/search/plugins/doc_printer.cc

--heuristic:

./driver/portfolio_runner.py
./src/search/search_algorithms/plugin_eager_greedy.cc
./src/search/search_algorithms/plugin_lazy_greedy.cc
./src/search/search_algorithms/plugin_lazy_wastar.cc
./src/search/command_line.cc
./src/search/plugins/doc_printer.cc

--landmarks:

./src/search/command_line.cc
./src/search/plugins/doc_printer.cc

Note that some of the uses of --heuristic and --evaluator and perhaps all of the usages of --landmarks are OK (= to provide the implementation of the legacy option support). We didn't filter this list.