If you're unsure if variable holds an int, you can validate its value:

#!/usr/bin/env bash
set -eu

vint() {
    local v
    for v; do
        if echo "$v" | egrep '[^0-9]' &> /dev/null; then
            printf '%s: %s: not an int\n' "$0" "$v" >&2
            exit 1
        fi
    done
}

vint "${A-}"
if (( ${A-} )); then
    echo true
else
    echo false
fi

The best solution I could find so far.

If you're unsure if variable holds an int, you can validate its value:

#!/usr/bin/env bash
set -eu

vint() {
    local v
    for v; do
        if echo "$v" | egrep '[^0-9]' &> /dev/null; then
            printf '%s: %s: not an int\n' "$0" "$v" >&2
            exit 1
        fi
    done
}

vint "${A-}"
if (( ${A-} )); then
    echo true
else
    echo false
fi

This is as far as I could take it.

If you're unsure if variable holds an int, you can validate its value:

#!/usr/bin/env bash
set -eu

vint() {
    local v
    for v; do
        if echo "$v" | egrep '[^0-9]' &> /dev/null; then
            printf '%s: %s: not an int\n' "$0" "$v" >&2
            exit 1
        fi
    done
}

vint "${A-}"
if (( ${A-} )); then
    echo true
else
    echo false
fi

The best solution I could find.

If you're unsure if variable holds an int, you can validate its value:

#!/usr/bin/env bash
set -eu

vint() {
    local v
    for v; do
        if echo "$v" | egrep '[^0-9]' &> /dev/null; then
            printf '%s: %s: not an int\n' "$0" "$v" >&2
            exit 1
        fi
    done
}

vint "${A-}"
if (( ${A-} )); then
    echo true
else
    echo false
fi

The best solution I could find so far.