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Add a math parameter to /data modify

Allow the /data modify to do math, similar to the /scoreboard players operation.

For example:
/data modify entity @s Items[0].Count math += value 10

The structure of the command would be the same, except instead of specifying "set", "append", "insert" etc... you specify "math" instead.

This would then be followed by the math operation, similar to the scoreboard operations.

  • +=, -=, *=, /=, %=, <, >

I would also suggest a couple others:

  • ^= Power
  • |= Root

The final part of the command would be the value, which similar to the other parameters, can be "value" or "from".

Why would this be useful?
Currently in order to modify data values, you need to store in a score, do operations, and then store back into data.

However, this limitation has 2 major problems:

  • Doubles, floats and Longs lose precision.
  • Three commands are executed for each operation

The /data modify math parameter would be only 1 command, and you can work directly with doubles, floats and Longs.

Working with arrays

The biggest advantage would be able to modify all values in an array, with only 1 command.

You can use a command such as /data modify block ~ ~ ~ Items[{id:"minecraft:dirt"].Count set value 10 to set all stack sizes, for dirt, in a chest to 10. This means that all values in an array are modified.

You cannot add or subtract to all values. A command like /data modify block ~ ~ ~ Items[{id:"minecraft:dirt"].Count math += value 1 would allow you to alter all the values.

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  • 5
    Registered User commented
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    That is great idea! Well thought.
    Mainly because dealing with "doubles" in scoreboards is horrible...

  • 1
    Registered User commented
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    I sorta agree with you, but ^ means xor in some programing languages like c and c#

     (im not sure about java)

    and | means or, i think these should be inmplemented in both modify functions along with & for bitwise and operations and << >> for bitshift operations.

    until this gets implemented I'd recommend you using 

     /execute store result score <entityname> <objectivename> run data get entity <entity with your nbt> <path to your nbt>

    to dump the nbt into a scoreboard and

    /execute store result entity <entity you want to store your score in> <your score> <datatype of your score> 1 run scoreboard players get <entity your score is saved in> <objectivename>

    to do the opposite, then you can use scoreboard operations on the scores

  • 0
    Registered User commented
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    This seems like a great idea, especially for working with types like longs, floats and doubles, which you can usually not do math with without losing precision.

    Just a detail, but I'd make it so that the result of the operation is converted back to the type of the input, so for example adding 2 to 3.5d would result in 5.5d and adding 3.5d to 2 would result in 5. The reason for that is that types need to be consistent in lists and therefore putting a double into a list of ints would fail.

  • 0
    Registered User commented
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    终于接近的要拥有一个真正的变量系统了，这是一件好事。