Comparing two characters in Xtend

[Hemal Bavishi]

Hello,

I found strange issue while comparing character in my program. Initially I used following way but it didn't work as it's taking 'P' as string

«IF(inputDataArgumentType == 'P')» «{appDataType = "*AppData" ""}»
«ELSE» «{appDataType = "AppData" ""}»

I found workaround by converting String to charArray and later used first instance or assign "P" to char type of variable and compare it later. 

«IF(inputDataArgumentType == 'P'.toCharArray.get(0))» «{appDataType = "*AppData" ""}»
«ELSE» «{appDataType = "AppData" ""}»

«val char pointer = "P"»
«IF(inputDataArgumentType == pointer)» «{appDataType = "*AppData" ""}»
«ELSE» «{appDataType = "AppData" ""}»
«ENDIF»

I am just wondering whether this is the way it's expected to behave or it's a bug?

Best Regards,

Hemal Bavishi

[Typhoon Storm]

Currently there is no char literal in Xtend. Join discussion at https://bugs.eclipse.org/bugs/show_bug.cgi?id=412383

I wrote a little helper method to overcome this:

    def static char !(String str) {

        if (str.length != 1)

            throw new RuntimeException("A char literal string must have length of 1! str = " + str)

        return str.charAt(0)

    }

Usage:

    def static void test(char x) {}

    

    def static void main(String[] args) {

        val x = !'a'

        println(x)

        test(x)

    }

It is good for me for its concise, that is you don't need to write 'a'.charAt(0) or assign 'a' to a char variable first. 

Will be good if this way is ok for all and can be added to Xtend's library.

[Sven Efftinge]

Hi Hemal,

as Typhoon already pointed out, there is no real char lteral atm.

The only thing that is available is auto cooercion if the expected type is char.

e.g.:

  val char x = ’c’

will be translated to

  final char x = ‘c’;

while

  val x = ‘c’

will be translated to

  final String x = “c”;

This works well in many cases but with generic methods like equals it doesn’t.

Sven

@Typhoon: I think if your helper method would have a char parameter, the compiler would do the conversion and checking for you.

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[Typhoon Storm]

Hi Sven,

Thanks for the information you gave, and I tried it out and to my surprise, it didn't work as expected. Code example is as follows:

class CharLiteralTest {

    def static char !(char ch) { // Did you mean this way?

        return ch

    }

//    def static char !(String str) {

//        if (str.length != 1)

//            throw new RuntimeException("A char literal string must have length of 1! str = " + str)

//        return str.charAt(0)

//    }

    

    def static void test(char x) {}

    

    def static void main(String[] args) {

        val x = !'a' // Compile error: ! cannot be resolved.

        val y = operator_not('a') // OK

        println(x)

        test(x)

        println(y)

        test(y)

    }

}

I also did a few other overloaded operator tests with the same result. So it seems auto coercion doesn't work for operator overloading.