We need a tag for "arithmetic expression building" challenges

Question

There's a popular type of maths puzzle where you get a list of digits (or numbers in general) and need to insert arithmetic operators in order to reach some target number. Every single time we get a challenge around this topic, I think "this looks so familiar, we must've done this before", but then I always fail to find a dupe target, because these challenges are near impossible to search for. The keywords that come to mind are things like "expression", "equation", "operator", "operation", "insert", "arithmetic", "Countdown", "Lettres et chiffres", etc. But these are all so horribly general that they turn up way more false positives than the actual challenges you're looking for. And then there's the problem that everyone seems to describe the problem differently, so you're probably overlooking some challenges all together.

But that's what tags are for. They group related challenges. If we introduced a tag for this, that would make it a lot easier for the experienced users to find existing challenges around this topic in order to look for duplicates. Of course it would also help people find similar (non-dupe) challenges similar to the one they've just solved, if they liked it.

So there's two things to this: a) coming up with a good tag name, b) finding all the relevant challenges so we can tag them. I've done some hunting just now, mostly via linked challenges and a few lucky keywords and here's what I dug up:

• Obtain a number from 4 numbers using any combination of mathematical operations
• Generate a valid equation using user-specified numbers
• Four fours puzzle
• Generate all possible integers
• It’s time to do the math
• Two-zero-one-five puzzle
• Arithmetic... tock... tick... tock
• Make a math equation from the date
• Find operations required to get result

There are also a few challenges where I'm not 100% sure whether they should be covered by the tag or not, but they're definitely closely related:

• generate a valid equation using specified operators asks you to insert the numbers given the operators. Still, this is about constructing an expression under some constraints which evaluates to a given result.
• Solve an equation with (almost) any numbers you like same here.
• Longest mathematical expression in a grid is closer to the problems above except that you are much more flexible in which numbers you use to construct the equation.

And then there's (at least) two challenges where you don't generate an expression given a list of digits, but instead you need to write a program which contains the digits in the given order and prints some result:

• 10 9 8 7 6 5 4 3 2 1... Print 2016
• Official Dyalog APL 2016 Year Game

These are definitely a bit different, but I feel like they're still in the same spirit.

As Mitch Schwartz pointed out in chat, certain metagolf challenges are also closely related. For example:

• Express a number with only 0-9 and the four operations
• Quickly express a number with only 0-9 and the four operations, plus one more extra

So, please let me know what you think about the utility of such a tag, what such a tag should cover, whether I've overlooked any challenges and of course any suggestions for a tag name.

Answer 1

I think having a tag for this is a good idea. The other solutions are great, but I'm going to throw out another one:

expression-building

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Edit

This seems to be the most popular solution, so I went ahead and created this tag. I'm going to slowly edit it into the questions that Martin has linked (to avoid flooding the front-page).

The tag wiki is here. Feel free to edit if you think you can improve clarity on it.

Answer 2

On Puzzling.SE, we use the tag formation-of-numbers for this purpose.

Answer 3

I think arithmetic-expression-building-challenge would be a pretty good choice.

On a more serious note, arithmetic-permutation would be good.