5

I have an array like this ...

a["a"]                = "aa"
a["b"]                = "ab"
a["c"]                = "ac"
a["d"]["a"]           = "ada"
a["d"]["b"]["a"]      = "adba"
a["e"]["a"]["a"]["a"] = "aeaaa"

... and want to clone it

clone(b, a)

This is what I tried so far :

function clone(lhs, rhs){

    for (i in rhs) {
        if (typeof(arr[i]) == "array"){
            clone(lhs[i], rhs[i])
        } else {
            lhs[i] = rhs[i]
        }
    }
}

But this clearly doesn't work because b["d"] is not created before that a["d"]["a"] is asigned to b["d"]["a"]. The second problem is that b["d"] should be typed as array.

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1 Answer 1

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5

You need to initialise the subarray before cloning into it:

function clone(lhs, rhs) {
    for (i in rhs) {
        if (isarray(rhs[i])) {
            lhs[i][1] = ""
            delete lhs[i][1]
            clone(lhs[i], rhs[i])
        } else {
            lhs[i] = rhs[i]
        }
    }
}

The write-value-then-delete it trick is mentioned in the gawk man page.

(I also fixed the array detection, using isarray.)

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  • See also copy_array() at stackoverflow.com/q/62179750/1745001 which I based on walk_array() from the gawk manual but is functionally almost identical to the above clone() function (with the arguments reversed) except that copy_array() will delete the target array (lhs above) before populating it and so ensures that the target ends up a copy of the original rather than a superset of the original array plus whatever the target array held previously. Commented Aug 24, 2020 at 14:44

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