There is a 32000 character limit for post that is inherited from the DB size of a field. It can be changed but we don’t. So another reply is added to continue the collection of knowledge.
From Jan W. (ref)
Without really answering your question, did you discover the SSU rules (Head => Body) and det/1? Since I use those, debugging time has been reduced a lot. Other recent goodies are trap/1 and gtrap/1 to quickly get the debugger at an exception. And of course, there is check/0 to do some static analysis, be it a lot less than mercury. And, last but not least the new “sweeprolog” mode for GNU emacs or the built-in Emacs clone save you a lot of work.
For creating a test case that mocks an external resourceby Jan W. (ref)
There is nothing out of the box. There are lots of options though. For example, implement a mock version of the library that calls the external service and load it instead of the real thing by changing the (library) search path. You can also use wrap_predicate/4 to create a wrapper around any predicate. That is intended to call the original, but of course you don’t need to. You can even abolish/1 the old predicate and assert a new definition.
None of that is portable. Wrapping predicates is really SWI-Prolog specific. There is no portability in search path handling (but many systems have it) and ISO turned
abolish/1into something useless because you can only use it on dynamic code where, in addition toretractall/1, it removes the predicate properties (dynamic, etc.) SWI-Prolog kept the pre-ISO semantics where abolish/1 applies to any predicate.Than you need an alternative implementation for the external server. I don’t know how much you can generalize that. I guess it can be anything.
Per Jan W. ([ref](https://Note that for indexing, atoms are faster than strings as atoms just look at the handle and strings actually need to access the text.))
Note that for indexing, atoms are faster than strings as atoms just look at the handle and strings actually need to access the text.
Per Jan W. (ref)
library(yall) is broken in the sense that the compiled behaviour differs from interpreted behaviour for variables shared with the rest of the clause. If you load the code without explicitly loading the library it is used interpreted. If you then use it and reload, it is compiled. So, always make sure library(yall) is loaded and make sure all meta-predicates through with it is called are loaded (or built-in). You can enable
:- set_prolog_flag(warn_autoload, true).
to get a warning about libraries that use goal/term expansion and are not loaded before the code is called. The default is still false. Might change to true shortly. It still occasionally gives a few somewhat misleading warnings 
If you use library(yall), you must really understand it I recommend using listing/1 on the predicates in which you use it to make sure it is compiled. Interpreted yall is semantically different and very slow.