如何在tcl中实现goto

Question

I wanted to know how to implement GOTO in tcl. I am writing a test case where I have say 5 steps. If my step 1 fails I don't want to proceed further and I want to skip the existing things and goto a common clean up section.

Please help me with if there are any GOTO commands in tcl.

Thanks, Ramya.

Answer 1

There is no goto in Tcl, and for relatively technical reasons it's impossible to implement one.

But you can do what you're after in other ways. Since you're dealing with test cases, I hope you're using the tcltest package for the job. With that, you can specify cleanup code quite easily:

tcltest::test test-1.1 "verify that the foo works" -setup {
    allocate some resources
} -body {
    whatever to do the test...
    return [our results]
} -cleanup {
    drop those resources
    make sure that we are nice and clean
} -result "the expected test result"

You can skip out of the body of a test easily by just doing a return ; the tcltest::test command will detect it and treat that as the result. It is usually better to try to keep each test independent of the others though: that makes it much easier to track down what's going wrong when a test fails.

If you're not using tcltest , you are still best refactoring into something where you can use return to skip out early. You can combine that with try…finally… (either natively in Tcl 8.6, or with this code on the Tcler's Wiki ) to make things easy:

proc doThings {} {
    try {
        # do thing-1
        if {$no_more} return
        # do thing-2
        if {$no_more} return
        # do thing-3
        if {$no_more} return
        # do thing-4
        if {$no_more} return
        # do thing-5
    } finally {
        # do cleanup
    }
}