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696 :: Conditional symbols

[2014-12-29T14:05:03+01:00]

yglukhov (orginal) [2014-12-29T14:05:03+01:00] view original

Is there a way to define a conditional symbol to have some value through nim command-line? What's the difference between --define:SYMBOL and --symbol:SYMBOL?

yglukhov (orginal) [2014-12-29T14:16:44+01:00] view original
Just found a workaround:
1. nim c --putEnv:my_symbol=my_value
2. const mySymbol = gorge("echo $my_symbol") But that really seems like a workaround. Windows code might need some changes.

Araq (orginal) [2014-12-29T14:57:51+01:00] view original

Don't do that.
--symbol:foo

declares the symbol but doesn't set it.

--define:foo

declares the symbol and sets it.

Now that most code out there has been updated to respect the defined vs declared split, --symbol won't be necessary in the upcoming releases anymore.

yglukhov (orginal) [2014-12-29T18:38:44+01:00] view original

declares the symbol and sets it.
Err.. sets it to what? =)

Do i use it like --define:foo=bar?

Araq (orginal) [2014-12-29T23:26:04+01:00] view original

It doesn't set it to any value, it just begins to exist. So after --define:foo on the command line defined(foo) in the Nim code is true.

yglukhov (orginal) [2014-12-30T11:34:28+01:00] view original

Ok, so returning to my original question, there is no way to give symbol a specific value in command line, right?

Araq (orginal) [2014-12-30T11:37:32+01:00] view original

That is correct. There are rumors that you can do os.getEnv("ENV_VAR") at compiletime, but really DO NOT DO THAT. Environment vars are machine specific global state, avoid them whenever you can.

yglukhov (orginal) [2014-12-30T12:23:07+01:00] view original

Ok, but you're not stating there's no need/plans for this feature, are you? =)