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In Java 3 = 12

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Re: In Java 3 = 12

#21

Post by Seol »

c8g wrote: post #10
sametmax wrote: post #8

Earlier quoted context omitted.

Yes but that's strange. Java is such a staticaly typed language you would not expect it to do that if you are like me and don't know it very well. While Python is very dynamic, but: >>> print(1 + 2 + "=" + 1 + 2) Traceback (most recent call last): File " ", line 1, in TypeError: unsupported operand type(s) for +: 'int' and 'str'

that's also strange to me. you are seeing this error because python is strong typing language. but this is weird that java is also strong typing language[0] 0: https://en.m.wikipedia.org/wiki/Java_(programming_language)

Strong v weak typing isn't an absolute categorisation, it's a spectrum. There aren't many places Java will automatically coerce types, and the ones that do exist are narrow (numeric promotion, string concatenation, and I can't think of any others).

Re: In Java 3 = 12

#22

Post by Seol »

badminton1 wrote: post #16

Things to consider here are: - operator precedence - implicit type casting - how operator+ is defined per each type (e.g: numbers add, strings concatenate)

The interesting thing is that the "obvious correct" behaviour would require the precedence of the + operator to depend on the types of the operands - which is obviously impossible if it's done at the parse stage...

Re: In Java 3 = 12

#23

Post by nicwilson »

struppi wrote: post #17

I suppose that's something every Java programmer should know: How types are automatically converted during "arithmetic" operations. There are some subtleties (like byte+short => int), but it's not too much to remember. The deeper question is: Was it a wise choice to disallow operator overloading BUT use "+" as a string concatination operator AND convert all values to strings during string concatenation? I think not,…

Thats why I'm glad D chose '~' as a binary concatenation operator so that there is never any confusion.

Re: In Java 3 = 12

#24

Post by Insanity »

I feel the title is a bit unfair. Technically it is '= + 1 + 2'. Which is expected as a Java developer.

Coming from other languages maybe it does look a bit odd though

Re: In Java 3 = 12

#26

Post by ubernostrum »

pmontra wrote: post #19
sametmax wrote: post #8

Earlier quoted context omitted.

Yes but that's strange. Java is such a staticaly typed language you would not expect it to do that if you are like me and don't know it very well. While Python is very dynamic, but: >>> print(1 + 2 + "=" + 1 + 2) Traceback (most recent call last): File " ", line 1, in TypeError: unsupported operand type(s) for +: 'int' and 'str'

Ruby is like Python, Perl and JavaScript are like Java. Type coercion has little to do with being strongly or weakly typed, dynamically or statically typed, interpreted or compiled, which are orthogonal axis. It's more like syntactic sugar to save a str(), a .to_s or a printf pattern. Maybe the Java implementation just overloads the + operator and converts the types inside it.

Strong/weak is not a useful thing most of the time, but when people do try to define it, often they do so in terms of the presence and number of implicit conversions the language will perform for you in order to allow operations to succeed despite being provided operands of the wrong type.

Also, overloading the "+" operator is basically what Java is doing, which is an odd inconsistency for a language which doesn't allow end-user code to do operator overloading.

Re: In Java 3 = 12

#27

Post by guelo »

pasquinelli wrote: post #9
sametmax wrote: post #8

Earlier quoted context omitted.

Yes but that's strange. Java is such a staticaly typed language you would not expect it to do that if you are like me and don't know it very well. While Python is very dynamic, but: >>> print(1 + 2 + "=" + 1 + 2) Traceback (most recent call last): File " ", line 1, in TypeError: unsupported operand type(s) for +: 'int' and 'str'

dynamic vs. static typing is independent of strong vs. weak typing. strong typing is basically allowing fewer implicit converstations, weak more. static means type checking happens before runtime, dynamic means the opposite.

Thanks for that explanation. So Java is weakly typed? Or would you say less strongly typed? Is the strength determined by the amount of implicit type coercions that are available?

Does static vs dynamic also imply that the strong-ness is checked at compile vs runtime? In other words, in python this bug can lurk undetected in your code

    list = (1, 2, 3)
    ‎x = list + 1
while in Java it will throw the error at compile time

    int[] list = {1, 2, 3}
    ‎Object x = list + 1

Re: In Java 3 = 12

#28

Post by Karliss »

My question is why shouldn't it be assuming there is no compiler error and funny pointer arithmetic. If surprising part was lack of error then 1 + "0" would be a sufficient example. Is left associativity and + operator precedence not being dependent on data types the surprising part?

Re: In Java 3 = 12

#29

Post by sametmax »

FascinatedBox wrote: post #20
sametmax wrote: post #8

Earlier quoted context omitted.

Yes but that's strange. Java is such a staticaly typed language you would not expect it to do that if you are like me and don't know it very well. While Python is very dynamic, but: >>> print(1 + 2 + "=" + 1 + 2) Traceback (most recent call last): File " ", line 1, in TypeError: unsupported operand type(s) for +: 'int' and 'str'

This is possible exactly because Java is statically-typed. Java's type system works over the operands, and does implicit conversions before the expression gets a chance to run. It sees values and does implicit magic from left to right. Python, on the other hand, does not need to do a typing pass at parse-time. Instead, literals are stored as values, and those values are tagged with their source class. Python's way of…

Actually Python does have a way to change addition semantics. It's just not defined for this operation.
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