chirp | A minimal Twitter clone to demonstrate Tornado and MongoDB

There are a couple of issues with your approach.

• Reading an entire line and trying to split it is more difficult than just reading each sound one at a time and outputting the animal. That also helps with the next issue since you don't need the array if you read word by word.
• Variable length arrays, like string sounds_filtered[sounds.size() - 1]; are not standard C++ and will not work on all compilers. If you need something like this consider a std::vector instead.
• cout << sounds_filtered; won't work, as you've noticed. You would need a loop to print each item in the array.
• using namespace std; may save you a bit of typing and seem more convenient but it can lead to difficult to diagnose problems when you have a name conflict. You can read more about that here if you like: Why is "using namespace std;" considered bad practice?

Here is an example of reading each sound one at a time and outputting the animal. I used a std::map to simplify matching the sound to the animal. You could use parallel arrays for this as you do in your example but it does make looking things up more difficult. If you do stick with the arrays I'd advise putting the lookup in a function to make the main loop easier to read.

Using the aggregation pipeline you can achieve the result you are looking for.

Stages:

1. Text search.
2. Sort by descending score, use the $meta aggregation expression in the $sort stage.
3. Split it and add a new field called matched-keywords.
4. Filter the matched-keywords using the $regexMatch.

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For this type of animation

Instead of drawing all points

First, you should never use assign; rather store the objects you create in a list. You can nornally do that like this

The following works for me:

There are a few ways to improve this but the simplest advice might be to build a single output string, add to it and write it to the console in a single statement, something like this (semi pseudo code):

There are quite a few things wrong with this code.

1. Sparrow and Canary are declared to conform to Flier yet doesn't say what their respective Other type is.

2. You are trying to pass both a parrot and a canary to sparrow.flockTogether(with:) and sparrow.sing(with:), but those methods only accept one type of object - Sparrow.Other. This, and the above point, suggest that you might be misunderstanding what associated types are. I suggest you read about them.

3. You are trying to access things that doesn't necessarily exist, such as f.name and f.sing(). Recall that f is an Other, which is not constrained to any type, so it can be anything. And "anything" won't always have a name for you to access.

I suggest the following to make the callers work:

1. Remove the associated type and use generic methods instead. Associated types are inappropriate if the caller gets to decide whether to pass in a Parrot or Canary.

2. Add name and sing() to Flier so that the compiler knows that anything conforming to Flier has those members. If we then constrain Other (the generic parameter of the aforementioned generic methods) to Flier, then we can access sing() and name without any problems.

3. Conform Parrot to Flier as well

The fixed code now looks like:

I think you're making this a lot more complex than it needs to be. Remember that many R functions are already vectorized. The following function will produce a linear chirp between frequencies f0 and f1 between t0 and t1, with an optional phi parameter to specify at what point on the cycle you want your sequence to begin:

I don't think there is a simple way to do this. You can, however, do a "one-liner" solution if you use pipes and for loops, things like that: