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Program entry

An executable Bubble has exactly one function named main. It may receive no arguments:

function main()
    print("Hello")
end

Or it may receive the command-line arguments as one Array<String> parameter:

function main(arguments: Array<String>)
    print(Array.length(arguments))
end

No other parameter shape is a valid native entry in 0.1.0-rc.3.

Exit status

Section titled “Exit status”

An entry with no result annotation finishes with status code zero when it reaches the end:

function main()
    print("done")
end

An entry may instead return an Int, which becomes the process exit status:

function main(): Int
    return 1
end

Shells conventionally interpret zero as success and a nonzero value as failure.

Arguments

Section titled “Arguments”

When using pop run, write program arguments after --:

Terminal window
pop run app.pop -- first "two words" ""

The entry receives three strings. The executable path itself is excluded. Order, empty arguments, and non-ASCII UTF-8 are preserved. If the operating system supplies an argument that is not valid UTF-8, the native entry traps before calling an argument-taking main rather than silently changing its bytes.

The entry declaration uses omitted/private visibility. Multiple main functions, another result type, multiple parameters, or a parameter other than Array<String> are rejected before native code is emitted.