max = 0
value = 0
LOOP
INPUT value
IF (value == 0)
EXIT LOOP
ENDIF
IF (value > max)
max = value
ENDIF
ENDLOOP
PRINT max
STOP
I am using https://marie.js.org/ but i'm having a lot of trouble trying to figure out how to do an if statement. I've attempted to use skipcond. I'm also struggling a bit with the endless loop. Any help to get me started off would be really appreciated.
First, convert the pseudo code to the if-goto style of assembly language & machine code.
if a then
b
endif
translates into
if !a then goto endif1
b
endif1,
Second, translate your pseudo code variables into Marie assembly language/machine code variables.
For example, you have an integer max in the pseudo code, so in the data area put:
max, dec 0
Finally, translate each line of if-goto code into assembly.
Conditional tests if a < b goto are done by comparison using subtraction. So, load a into the accumulator, subtract b, which sets the condition codes, and then do a SkipCond and goto to skip or not skip code you want to execute.
Marie.js has a number of simple examples. Look at the multiplication example, to see data/variable declarations, conditional branches, loops, input, output.
I'm trying to check if a variable I have is equals to NaN in my Ruby on Rails application.
I saw this answer, but it's not really useful because in my code I want to return 0 if the variable is NaN and the value otherwise:
return (average.nan ? 0 : average.round(1))
The problem is that if the number is not a NaN I get this error:
NoMethodError: undefined method `nan?' for 10:Fixnum
I can't check if the number is a Float instance because it is in both cases (probably, I'm calculating an average).
What can I do?
It is strange only to me that a function to check if a variable is equals to NaN is avaible only to NaN objects?
Quickest way is to use this:
under_the_test.to_f.nan? # gives you true/false e.g.:
123.to_f.nan? # => false
(123/0.0).to_f.nan? #=> true
Also note that only Floats have #nan? method defined on them, that's the reason why I'm using #to_f in order to convert result to float first.
Tip: if you have integer calculation that potentially can divide by zero this will not work:
(123/0).to_f.nan?
Because both 123 and 0 are integers and that will throw ZeroDivisionError, in order to overcome that issue Float::NAN constant can be useful - for example like this:
return Float::NAN if divisor == 0
return x / divisor
I found this answer while duckducking for something that is neither NaN nor Infinity (e.g., a finite number). Hence I'll add my discovery here for next googlers.
And as always in ruby, the answer was just to type my expectation while searching in the Float documentation, and find finite?
n = 1/0.0 #=> Infinity
n.nan? #=> false
n.finite? #=> false
The best way to avoid this kind of problem is to rely on the fact that a NaN isn't even equal to itself:
a = 0.0/0.0
a != a
# -> True !
This is likely not going to be an issue with any other type.
Is it possible to use DECODE on a SUM field ?
For example, something like this :
DECODE( SUM("QTA' CONV SUM 1 2 2"),'>0',1,'=0',0)
In your specific case, where you want the result to be 1 if the SUM is greater than zero or 0 if the SUM is zero, you can use the Oracle SIGN function. I'm not sure if there's any special Discoverer syntax, but outside of Discoverer I'd do it something like this:
SIGN(SUM(whatever you're summing))
The "techonthenet" site documents the function here.
An alternative to #EdGibbs, if the values that you're summing are integers:
Greatest(Sum(...),1)
If you had negatives to contend with then maybe:
Least(Greatest(Sum(...),1),0)
The syntax gets a bit gnarly so if you did want to stick with Decode or Case then:
Case Sum(...)
When 0 Then 0
Else 1
End
... or ...
Decode(Sum(...),0,0,Sum(...))
I wouldn't go for a solution that repeats the Sum() though. Keep it DRY
I was coding here the other day, writing a couple of if statements with integers that are always either 0 or 1 (practically acting as bools). I asked myself:
When testing for positive result, which is better; testing for int == 1 or int != 0?
For example, given an int n, if I want to test if it's true, should I use n == 1 or n != 0?
Is there any difference at all in regards to speed, processing power, etc?
Please ignore the fact that the int may being more/less than 1/0, it is irrelevant and does not occur.
Human's brain better process statements that don't contain negations, which makes "int == 1" better way.
It really depends. If you're using a language that supports booleans, you should use the boolean, not an integer, ie:
if (value == false)
or
if (value == true)
That being said, with real boolean types, it's perfectly valid (and typically nicer) to just write:
if (!value)
or
if (value)
There is really very little reason in most modern languages to ever use an integer for a boolean operation.
That being said, if you're using a language which does not support booleans directly, the best option here really depends on how you're defining true and false. Often, false is 0, and true is anything other than 0. In that situation, using if (i == 0) (for false check) and if (i != 0) for true checking.
If you're guaranteed that 0 and 1 are the only two values, I'd probably use if (i == 1) since a negation is more complex, and more likely to lead to maintenance bugs.
If you're working with values that can only be 1 or 0, then I suggest you use boolean values to begin with and then just do if (bool) or if (!bool).
In language where int that are not 0 represents the boolean value 'true', and 0 'false', like C, I will tend to use if (int != 0) because it represents the same meaning as if (int) whereas int == 1 represents more the integer value being equal to 1 rather than the boolean true. It may be just me though. In languages that support the boolean type, always use it rather than ints.
A Daft question really. If you're testing for 1, test for 1, if you're testing for zero, test for zero.
The addition of an else statement can make the choice can seem arbitrary. I'd choose which makes the most sense, or has more contextual significance, default or 'natural' behaviour suggested by expected frequency of occurrence for example.
This choice between int == 0 and int != 1 may very well boil down to subjective evaluations which probably aren't worth worrying about.
Two points:
1) As noted above, being more explicit is a win. If you add something to an empty list you not only want its size to be not zero, but you also want it to be explicitly 1.
2) You may want to do
(1 == int)
That way if you forget an = you'll end up with a compile error rather than a debugging session.
To be honest if the value of int is just 1 or 0 you could even say:
if (int)
and that would be the same as saying
if (int != 0)
but you probably would want to use
if (int == 1)
because not zero would potentially let the answer be something other than 1 even though you said not to worry about it.
If only two values are possible, then I would use the first:
if(int == 1)
because it is more explicit. If there were no constraint on the values, I would think otherwise.
IF INT IS 1
NEXT SENTENCE
ELSE MOVE "INT IS NOT ONE" TO MESSAGE.
As others have said, using == is frequently easier to read than using !=.
That said, most processors have a specific compare-to-zero operation. It depends on the specific compiler, processor, et cetera, but there may be an almost immeasurably small speed benefit to using != 0 over == 1 as a result.
Most languages will let you use if (int) and if (!int), though, which is both more readable and get you that minuscule speed bonus.
I'm paranoid. If a value is either 0 or 1 then it might be 2. May be not today, may be not tomorrow, but some maintenance programmer is going to do something weird in a subclass. Sometimes I make mistakes myself [shh, don't tell my employer]. So, make the code say tell me that the value is either 0 or 1, otherwise it cries to mummy.
if (i == 0) {
... 0 stuff ...
} else if (i == 1) {
... 1 stuff ...
} else {
throw new Error();
}
(You might prefer switch - I find its syntax in curly brace language too heavy.)
When using integers as booleans, I prefer to interpret them as follows: false = 0, true = non-zero.
I would write the condition statements as int == 0 and int != 0.
I would say it depends on the semantics, if you condition means
while ( ! abort ) negation is ok.
if ( quit ) break; would be also ok.
if( is_numeric( $int ) ) { its a number }
elseif( !$int ) { $int is not set or false }
else { its set but its not a number }
end of discussion :P
I agree with what most people have said in this post. It's much more efficient to use boolean values if you have one of two distinct possibilities. It also makes the code a lot easier to read and interpret.
if(bool) { ... }
I was from the c world. At first I don't understand much about objective-c. After some while, I prefer something like:
if (int == YES)
or
if (int == NO)
in c, i.e.:
if (int == true)
if (int == false)
these days, I use varchar instead of integer as table keys too, e.g.
name marital_status
------ --------------
john single
joe married
is a lot better than:
name marital_status
------ --------------
john S
joe M
or
name marital_status
------ --------------
john 1
joe 2
(Assuming your ints can only be 1 or 0) The two statements are logically equivalent. I'd recommend using the == syntax though because I think it's clearer to most people when you don't introduce unnecessary negations.
Is it better to use NOT or to use <> when comparing values in VBScript?
is this:
If NOT value1 = value2 Then
or this:
If value1 <> value2 Then
better?
EDIT:
Here is my counterargument.
When looking to logically negate a Boolean value you would use the NOT operator, so this is correct:
If NOT boolValue1 Then
and when a comparison is made in the case of the first example a Boolean value is returned. either the values are equal True, or they are not False. So using the NOT operator would be appropriate, because you are logically negating a Boolean value.
For readability placing the comparison in parenthesis would probably help.
The latter (<>), because the meaning of the former isn't clear unless you have a perfect understanding of the order of operations as it applies to the Not and = operators: a subtlety which is easy to miss.
Because "not ... =" is two operations and "<>" is only one, it is faster to use "<>".Here is a quick experiment to prove it:
StartTime = Timer
For x = 1 to 100000000
If 4 <> 3 Then
End if
Next
WScript.echo Timer-StartTime
StartTime = Timer
For x = 1 to 100000000
If Not (4 = 3) Then
End if
Next
WScript.echo Timer-StartTime
The results I get on my machine:
4.783203
5.552734
Agreed, code readability is very important for others, but more importantly yourself. Imagine how difficult it would be to understand the first example in comparison to the second.
If code takes more than a few seconds to read (understand), perhaps there is a better way to write it. In this case, the second way.
The second example would be the one to go with, not just for readability, but because of the fact that in the first example, If NOT value1 would return a boolean value to be compared against value2. IOW, you need to rewrite that example as
If NOT (value1 = value2)
which just makes the use of the NOT keyword pointless.