I have a set of if then statements that exceed 20 24 to be exact. I am using them to select when sunrise starts and sunset starts. I know I could use case statements as well but can anyone point me to what is meant by a nested IF. IS this a limit to just 20 if statements in a program or how do they have to be separated not to be considered nested. I looked in the commands but didn't see this limit mentioned.
If nesting limit
- Thread starter Kecked
- Start date
Not necessarily. It's more likely to be translated into GOTO on <condition> rather than GOSUB on <condition>. And this idea is enforced by this working in the simulator:The limit is almost certainly the Picaxe stack - I think it is 8 deep
Code:
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
if b0 = 0 then
do : loop
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end ifnick has it the way I have it. That's why I was wondering why it is called nested when its all in a row like nick shows. That doesn't seem nested to me. Will I have the same issue with case statement? BTW I only used a single endif. Its 24 if thens followed by a single endif.
I'm using two pins to trigger a second micro (I needed more pwms for the leds) so when 10 its sunrise when 01 its sunset. when 00 or 11 don't care. Here is the section it bitches about as nested. I'll redo it as case statements
I'm using two pins to trigger a second micro (I needed more pwms for the leds) so when 10 its sunrise when 01 its sunset. when 00 or 11 don't care. Here is the section it bitches about as nested. I'll redo it as case statements
Code:
'January
if month=1 and w22=8 then high b.1:low b.2
if month=1 and w22=18 then low b.1:high b.2
'February
if month=2 and w22=8 then high b.1:low b.2
if month=2 and w22=18 then low b.1:high b.2
'March
if month=3 and w22=8 then high b.1:low b.2
if month=3 and w22=18 then low b.1:high b.2
'April
if month=4 and w22=8 then high b.1:low b.2
if month=4 and w22=18 then low b.1:high b.2
'May
if month=5 and w22=8 then high b.1:low b.2
if month=5 and w22=18 then low b.1:high b.2
'June
if month=6 and w22=8 then high b.1:low b.2
if month=6 and w22=18 then low b.1:high b.2
'July
if month=7 and w22=8 then high b.1:low b.2
if month=7 and w22=18 then low b.1:high b.2
'August
if month=8 and w22=8 then high b.1:low b.2
if month=8 and w22=18 then low b.1:high b.2
'September
if month=9 and w22=8 then high b.1:low b.2
if month=9 and w22=18 then low b.1:high b.2
'October
if month=10 and w22=8 then high b.1:low b.2
if month=10 and w22=18 then low b.1:high b.2
'November
if month=11 and w22=8 then high b.1:low b.2
if month=11 and w22=18 then low b.1:high b.201
'December
if month=12 and w22=8 then high b.1:low b.2
if month=12 and w22=18 then low b.1:high b.2
endifinglewoodpete
Senior Member
Kecked, The code you posted in #5 is nested 1 deep. Well within the capability of the PICAXE and the PE.
g6ejd's post in #3 is correct. Note that nested "Ifs" do not take up stack space, so the only resource used is program memory.
Stack space is only consumed by GoSubs and interrupts; and only then when a GoSub calls a GoSub calls a GoSub etc (nested GoSubs).
g6ejd's post in #3 is correct. Note that nested "Ifs" do not take up stack space, so the only resource used is program memory.
Stack space is only consumed by GoSubs and interrupts; and only then when a GoSub calls a GoSub calls a GoSub etc (nested GoSubs).
westaust55
Moderator
As discussed a couple of years ago there is a nexting limit for IF...THEN statements of 20.
This still applies with the V5.5.1 PE.
inglewoodpete
Senior Member
I've not tested the limits before. I get a maximum of 19 but it reports a strange error: "Error: can't write to object file."
westaust55
Moderator
Yes there is a problem with the Programming Editor V5.5.1 when right on the limit.
Less than 20 nested IF...THEN's and all is well.
at 20 nested IF...THEN's there is the error as IWP states:
at 21 nested IF...THEN's there is the expected error message:
Less than 20 nested IF...THEN's and all is well.
at 20 nested IF...THEN's there is the error as IWP states:
"Error: can't write to object file |"
at 21 nested IF...THEN's there is the expected error message:
"Error: If nesting limit (20) exceeded
Attachments
The Problem with the code in Post 5 is not so much that the nesting limit has been exceeded but that the syntax is wrong. The compiler just caught a nesting limit first. Remove November & December to comply with the nesting limit and you get the syntax " If without Endif".
Certainly these "if" lines should not be "nested" anyway since the first if in the nest is " if month=1 and w22=8 ", which means none of the other lines could ever be true.
Just add an endif at the end of each line like this:
if month=1 and w22=8 then high b.1:low b.2 : endif
But ... I am not sure what you are trying to do with the code, since the same action is performed regardless of month. So it seems that the code needs to be refined.
Certainly these "if" lines should not be "nested" anyway since the first if in the nest is " if month=1 and w22=8 ", which means none of the other lines could ever be true.
Just add an endif at the end of each line like this:
if month=1 and w22=8 then high b.1:low b.2 : endif
But ... I am not sure what you are trying to do with the code, since the same action is performed regardless of month. So it seems that the code needs to be refined.
Last edited:
We will investigate. Probably the error handler putting up an incorrect error message.
Here I think is a more eliquent solution. All I am doing is setting a set of pins high and low to trigger separate chips to do the sunrise and sunset. I ran out of pwms so that was my solution. My final solution will probaly use on of the 16 channel pwm chips. That is why I used two ports so I can address that chip later. I'm also going to dump this approach in favor of a real calculation once I learn this FPU chip.
Code:
'Sunrise
Let b27=bcdtobin month
Lookup b27, (8,7,7,7,6,6,6,7,7,8,8,8), b28 'sunrise
Lookup b27, (17,18,20, 20,20,21,21,21,21,20,19,18,17), b29 'sunset
if hour=b28 then high b.2 :low b.1:endif 'sunrise
if hour=b29 then low b.2 :high b.1:endif 'sunset
Last edited: