```// 1 regexBuilder.append( alts.split("|") ...

# codingconventions

[Ellen Spertus]

// 1
regexBuilder.append(
    alts.split("|")
        .map { it.trim() }
        .map { if (it.isEmpty()) "" else " $it"}
        .joinToString(prefix = "(?:", separator = "|", postfix = ")"))

or

// 2
regexBuilder.append(
    alts.split("|")
        .map { it.trim() }.joinToString(
             prefix = "(?:",
             separator = "|",
             postfix = ")"
        ) { if (it.isEmpty()) "" else " $it" })

[diesieben07]

alts.split("|")
        .map { it.trim() }
        .joinTo(regexBuilder, prefix = "(?:", separator = "|", postfix = ")") {
            if (it.isEmpty()) "" else " $it"
        }

[diesieben07]

Actually, even better: (Not equivalent!)

alts.split("|")
        .map { it.trim() }
        .filter { it.isNotEmpty() }
        .joinTo(regexBuilder, prefix = "(?:", separator = "|", postfix = ")")

[Ellen Spertus]

Thanks, @diesieben07! My favorite answer is “none of the above”.

[diesieben07]

haha, sorry. If only 1 or 2 are possible then definitely 2, but formatted differently, there should be a \n before joinToString

[Ellen Spertus]

Empty elements are allowed. For example, “foo | bar | ” should become ” foo| bar|”

[Ellen Spertus]

I wasn’t being sarcastic. I learn the most from “none of the above”, and it takes the most effort on the part of the writer, so thank you.

[Ellen Spertus]

For a collection of String, are joinTo and joinToString equivalent?

[diesieben07]

Ah, so you are right, my 2nd solution is not equivalent

[diesieben07]

joinTo works on Appendable, like StringBuilder

[diesieben07]

It avoids the intermediary String

[diesieben07]

So foo.append(thing.joinToString() and thing.joinTo(foo) are the same

[Ellen Spertus]

Thanks so much!

[Ellen Spertus]

I’ve been changing other code of mine to use joinTo. My final code will be so elegant that it will go ballroom dancing. 💃 🕺