| Wed May 25 04:46:15 2016 by wyrdR |
| Hi Torben, Any chance of implementing NOT operator (or undefined), optional and default variables in Troll? Any attempt to reference a non-existent variable throws "Runtime error: unknown variable" i.e. A variable, whereby, if you DO NOT specify it on the command line, it will DEFAULT to a value in the definition. e.g. x:=if !x then -1 else x; \ If x not defined, is empty or doesn't exist, the x = -1, don't throw an error \\or x:=if defined x then x else -1; \ If x not defined, the x = -1, don't throw an error \\or define x; \ x is defined but has no value; It will be assigned later or from an argument Thanks wyrdR |
| Wed May 25 09:58:49 2016 by Torben |
| A negation operator would be fairly easy to implement, but in the mean time, you can just flip the branches of a conditional and use while instead of until (and vice-versa) in loops. I'm not entirely happy about the idea of giving undeclared variables default values, as that will make some errors go unnoticed. An operator that will return the value of x if this is defined but a specified value if not is a possibility, though. I will think about it. |
| Fri Jun 3 09:08:26 2016 by Torben |
| Out of curiosity, what would you want to use default values for? It does not make sense for initialising a loop variable, as that is not how loops work (you can not reassign a new value to an existing variable). |
| Fri Jun 3 20:36:35 2016 by Ron Vantreese |
| I came across this piece of information that might give you some ideas: https://msdn.microsoft.com/en-us/library/2cf62fcy.aspx Near the bottom is a table describing how a nullable variable behaves in a logical test. Granted, it's about Boolean, but the same concept can be applied to other variables. Returning a value if an object is null? Sometimes I get this value "(null)" when attempting to access a null object. |
| Sat Jun 4 08:19:36 2016 by wyrdR |
| I want optional variables on the command line, making certain definitions more flexible. Cheers wyrdR |
| Tue Jun 7 14:31:39 2016 by Torben |
| I have now added negation and default values. The negation operator is called ! (like in C). ! e is an abbreviation for if e then {} else 1.The default value construction x ~ e checks if x is defined. If it is, its value is returned. Otherwise, the value of e is returned.If hope this solves your problem. |
| Wed Jun 8 02:20:56 2016 by wyrdR |
| Thanks Torben, That's awesomeness! |
| Wed Sep 7 23:04:55 2016 by Jeoshua |
| Speaking of the ! operator, does anyone else find the "not equals" notation cumbersome? =/= may look like "does not equal" but it flies in the face of notation in most other programming languages. I would greatly prefer "!=" to mean "does not equal" as a filter. |
| Thu Sep 8 09:49:56 2016 by Torben |
| =/= is used for "not equal to" in Erlang, Prolog, Fortress and possibly a few other languages. So while the C crowd (including C-derived languages like Java and C#) may find it unfamiliar, its use is not unique to Troll. Languages before C mostly used <>, .NE. or NE for inequality, but that is even farther from the mathematical symbol ≠. Some languages (such as Haskell and modern Fortran) use /=. |