RE: How to compare two floats?
Unless you need the enhance dynamic range abilities of floating point, you shouldn't be using it at all. That's just a general principle. Devcie temperatures are well handled by fixed-point (integer) routines. -- Jim -Original Message- From: busybox [mailto:busybox-boun...@busybox.net] On Behalf Of bifferos Sent: Sunday, May 24, 2015 4:05 AM To: Lauri Kasanen; busybox@busybox.net Subject: Re: How to compare two floats? Thanks for all the responses to this, it's given me some ideas. regards, Biff. From: Lauri Kasanen cur...@operamail.com To: busybox@busybox.net Sent: Sunday, 24 May 2015, 8:40 Subject: Re: How to compare two floats? On Saturday 23 May 2015 21:41:51 bifferos wrote: I'm trying to write a thermostat using busybox shell, however the only way I could think to compare two float temperatures (without adding awk) was to multiply them up in dc and then compare as integers. In the end I modified dc to add a comparison operator, which probably breaks the spirit of dc somewhat. I'm interested if I missed a trick somewhere. Is there another way to do this? Is this considered a heinous thing to do to dc? a - b Then you check if the sign is negative, using the shell's string ops. - Lauri -- http://www.fastmail.com - Access all of your messages and folders wherever you are ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
Re: How to compare two floats?
Thanks for all the responses to this, it's given me some ideas. regards, Biff. From: Lauri Kasanen cur...@operamail.com To: busybox@busybox.net Sent: Sunday, 24 May 2015, 8:40 Subject: Re: How to compare two floats? On Saturday 23 May 2015 21:41:51 bifferos wrote: I'm trying to write a thermostat using busybox shell, however the only way I could think to compare two float temperatures (without adding awk) was to multiply them up in dc and then compare as integers. In the end I modified dc to add a comparison operator, which probably breaks the spirit of dc somewhat. I'm interested if I missed a trick somewhere. Is there another way to do this? Is this considered a heinous thing to do to dc? a - b Then you check if the sign is negative, using the shell's string ops. - Lauri -- http://www.fastmail.com - Access all of your messages and folders wherever you are ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
Re: How to compare two floats?
On Saturday 23 May 2015 21:41:51 bifferos wrote: I'm trying to write a thermostat using busybox shell, however the only way I could think to compare two float temperatures (without adding awk) was to multiply them up in dc and then compare as integers. In the end I modified dc to add a comparison operator, which probably breaks the spirit of dc somewhat. I'm interested if I missed a trick somewhere. Is there another way to do this? Is this considered a heinous thing to do to dc? a - b Then you check if the sign is negative, using the shell's string ops. - Lauri -- http://www.fastmail.com - Access all of your messages and folders wherever you are ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
Re: How to compare two floats?
On Saturday 23 May 2015 21:41:51 bifferos wrote:
I'm trying to write a thermostat using busybox shell, however the only way I
could think to compare two float temperatures (without adding awk) was to
multiply them up in dc and then compare as integers. In the end I modified
dc to add a comparison operator, which probably breaks the spirit of dc
somewhat. I'm interested if I missed a trick somewhere. Is there another
way to do this? Is this considered a heinous thing to do to dc?
Thanks,Biff.
--- a/miscutils/dc.c
+++ b/miscutils/dc.c
@@ -103,6 +103,18 @@ static void divide(void)
push(pop() / divisor);
}
+static void gt(void)
+{
+ double rhs = pop();
+ push((pop() rhs) ? 1 : 0);
+}
+
+static void ge(void)
+{
+ double rhs = pop();
+ push((pop() = rhs) ? 1 : 0);
+}
+
static void mod(void)
{
data_t d = pop();
@@ -204,6 +216,8 @@ static const struct op operators[] = {
{mul, mul},
{/, divide},
{div, divide},
+ {gt, gt},
+ {ge, ge},
#if ENABLE_FEATURE_DC_LIBM
{**, power},
{exp, power},
Hi,
is the number of decimal digits fixed? If yes
something like this could work:
debian:~$ SEP='.'
debian:~$ T1=`echo 19.2 | tr -d '$SEP'`
debian:~$ echo $T1
192
debian:~$ T2=`echo 20.0 | tr -d '$SEP'`
debian:~$ echo $T2
200
debian:~$ if [ $T1 -le $T2 ] ; then echo $T2; else echo $T1; fi
200
if the number of decimal digits is not fixed it is a little more
complicated as they need to be padded (with printf ?).
Just my 0.2 cents.
Ciao,
Tito
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How to compare two floats?
I'm trying to write a thermostat using busybox shell, however the only way I
could think to compare two float temperatures (without adding awk) was to
multiply them up in dc and then compare as integers.
In the end I modified dc to add a comparison operator, which probably breaks
the spirit of dc somewhat. I'm interested if I missed a trick somewhere. Is
there another way to do this? Is this considered a heinous thing to do to dc?
Thanks,Biff.
--- a/miscutils/dc.c
+++ b/miscutils/dc.c
@@ -103,6 +103,18 @@ static void divide(void)
push(pop() / divisor);
}
+static void gt(void)
+{
+ double rhs = pop();
+ push((pop() rhs) ? 1 : 0);
+}
+
+static void ge(void)
+{
+ double rhs = pop();
+ push((pop() = rhs) ? 1 : 0);
+}
+
static void mod(void)
{
data_t d = pop();
@@ -204,6 +216,8 @@ static const struct op operators[] = {
{mul, mul},
{/, divide},
{div, divide},
+ {gt, gt},
+ {ge, ge},
#if ENABLE_FEATURE_DC_LIBM
{**, power},
{exp, power},
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