OpenEuphoria

chk_pow_args() (to Andy)

• Posted by rolf.schroeder at desy.de Jun 14, 2002
• 461 views

Andy, 

Here a corrected version which accounts also for 0^b, b!=0. I forgot
this case. But some more checks of this functions are recommended!

Have a nice day, Rolf

-------------------------------------------------------------------
constant lim = log(3e+307)  -- needed for chk_pow_args()
-------------------------------------------------------------------

function chk_pow_args(object a, object b)
--       ------------
    if atom(a) and atom(b) then
        if a > 0.0 then
            if b*log(a) < lim then
                return 1
            end if
        elsif a < 0 then
            if integer(b) then
                if b*log(-a) < lim then
                    return 1
                end if
            else
                return 0
            end if
        elsif b != 0.0 then -- case a=0 !
            return 1
        end if
        return 0
    elsif length(a) = length(b) then
        for i = 1 to length(a) do
            if not chk_pow_args(a[i],b[i]) then
                return 0
            end if
        end for
    end if
    return 0
end function
-------------------------------------------------------------------

procedure test(atom a, atom b)
--        ----
    if chk_pow_args(a,b) then
        printf(1,"%24.15g%24.15g%24.15g\n",{a,b, power(a,b)})
    else
        printf(1,"%24.15g%24.15g  %s\n",{a,b,"power(a,b) failed!"})
    --  puts(1,"power() failiour! Abort.\n")
    end if
end procedure
-------------------------------------------------------------------
    test( 0.0950052, -300.784)
    test( 0.0950053, -300.784)
    test(-0.0950053, -300.784)
    test( 3.01     ,  -30.000)
    test(-3.01     ,  -30.000)
    test( 3.01     ,  -31.000)
    test(-3.01     ,  -31.000)
    test(-3.01     ,-9100.000)
    test(-3.01     ,-1e+9    )
    test(-3.01     ,-1e+10   )
    test( 3.01     ,-1e+9    )
    test( 3.01     ,-1e+10   )
    test( 1.01e+300,    1.01 )
    test( 1.01e+300,   -1.01 )
    sequence s, t
    s = { 0.0950052, 0.0950052, -0.0950053}
    t = { -300.784 , -300.784 , -300.784  }
    ? s ? t ? chk_pow_args(s,t)
    s = { 0.0950052, 0.0950052, -0.0950052 , 1}
    t = { -300.784 , -300.784 , -300.784  }
    ? s ? t ? chk_pow_args(s,t)
    abort(0)
-------------------------------------------------------------------