> > My 0,02 €, which is just a personal opinion: > > I think that handling manually "!/not" would be worth the effort rather > than having two commands, especially if the boolean expression syntax may > be extended some day and the negative if would become obsolete. > > If there is a negative condition syntax, I would slightly prefer \ifnot to > \if_not or worse \unless. I would disaprove strongly of \unless because it > looses the clear symmetry with a closing \fi. > > -- > Fabien.
Pavel had previously written this patch http://ftp.pgpi.org/pub/databases/postgresql/projects/pgFoundry/epsql/epsql/epsql-8.5-develop/psql-enhanced-macros.diff which I leave here as a point of reference. Obviously, there's a lot more in there than we'd need, and it's back quite a few versions. I agree that the boolean tests available should be *very* simple, and all of the weight of complex calculation should be put in SQL, like we do with \gset I propose those be: \if STRING : true if STRING evaluates to true via ParseVariableBool, empty means false \ifnot STRING: true if STRING evaluates to false via ParseVariableBool, empty means false \ifdef psql_var: true if psql_var is defined \ifndef psql_var: true if psql_var is not defined, helpful for when --set var=val was omitted and should be defaulted A full compliment of \elseif \elseifnot \elseifdef \elseifndef, each matching the corresponding \if* above. I'm ok with these being optional in the first revision. \else - technically we could leave this out as well \endif Then seems like we need an if-state-stack to handle nesting. At any given point, the mode could be: 1. None psql currently isn't in an if-then structure, no non-conditional statements are skipped. any conditional commands other than \if* are an error. For that matter, the script can always add a new level to the stack with an \if* command. 2. If-Then psql is currently executing statements in an \if* branch that evaluated to true. valid conditional commands are: \if*, \else* \endif 3. If-Skip psql is currently in a block that evaluated to false, and will still parse commands for psql-correctness, but will skip them until it encounters an \endif or \else* 4. Else-Then Just like If-Then, but encountering an \else* command would be an error. 5. Else-Skip Just like If-Skip, but encountering an \else* command would be an error. The only data structure we'd need is the stack of enums listed above. Any commands would check against the stack-state before executing, but would otherwise be parsed and checked as they are now. The new \commands would manipulate that stack. Does that seem work-able?
