Comparing integers - without calling the shell

[ftonneau]

In the infamous series:

Branching on a boolean option -- without calling the shell

In Kakoune scripts, branching on the value of a boolean option, myvar, may be done by calling the shell inside a try ... catch construction: try %{ evaluate-commands %sh{ if [ "$kak_opt_myvar" = false ]; then printf %s\\n fail fi } commands_1 } \ catch %{ commands_2 } which looks bloated and contorted to me. (One could use a wrapper to make the code look simpler, but then the wrapper needs to be defined elsewhere.) Recently I have been using a trick…

here is another dirty hack to compare non-negative integers in Kakoune, without calling the shell. The hack depends on subtracting an integer from another integer with the set -add command, as well as the behavior of echo: when followed by a non-negative integer, echo does its job, but when followed by a negative integer (e.g., -3), echo interprets the leading minus sign as the start of an option and protests (‘unknown option’).

Here is the code:

declare-option -hidden int int_running_sum

define-command \
-params 2 \
equal-to %{
    less-or-equal %arg(1) %arg(2)
    greater-or-equal %arg(1) %arg(2)
}

define-command \
-params 2 \
different-from %{
    try %{
        less-than %arg(1) %arg(2)
    } \
    catch %{
        greater-than %arg(1) %arg(2)
    }
}

define-command \
-params 2 \
less-than %{
    set window int_running_sum %arg(2)
    set -add window int_running_sum "-%arg(1)"
    set -add window int_running_sum -1
    evaluate-commands -draft %{
        echo %opt(int_running_sum)
    }
}

define-command \
-params 2 \
less-or-equal %{
    set window int_running_sum %arg(2)
    set -add window int_running_sum "-%arg(1)"
    evaluate-commands -draft %{
        echo %opt(int_running_sum)
    }
}

define-command \
-params 2 \
greater-than %{
    set window int_running_sum %arg(1)
    set -add window int_running_sum "-%arg(2)"
    set -add window int_running_sum -1
    evaluate-commands %{
        echo %opt(int_running_sum)
    }
}

define-command \
-params 2 \
greater-or-equal %{
    set window int_running_sum %arg(1)
    set -add window int_running_sum "-%arg(2)"
    evaluate-commands %{
        echo %opt(int_running_sum)
    }
}

Enjoy … or not!

(I do have one use case for this sort of trick.)

[danr]

echo does its job, but when followed by a negative integer (e.g., -3), echo interprets the leading minus sign as the start of an option and protests (‘unknown option’)

Gwahahaha, that’s just… great.