I understand that the string_variable(start:length) can be used to get a substring of a string given a starting point and substring length, however, I am finding that I often need to get a substring between a 'start' and 'end' point.
While I know I could always do this:
SUBTRACT start FROM end GIVING len
string(start:len)
It seems cumbersome to have to do so every time when I am writing programs that use this functionality often. Is there perhaps a quicker/built-in way of achieving this?
How about?
move str (start-pos : end-pos - start-pos + 1) to ...
You can subtract the first from the last, but you need to add 1 to get the correct length.
STRING is a statement name, as is START, and END is reserved. LENGTH is a function name. I avoid those in anything that looks like code.
Related
I have different commands my program is reading in (i.e., print, count, min, max, etc.). These words can also include a number at the end of them (i.e., print3, count1, min2, max6, etc.). I'm trying to figure out a way to extract the command and the number so that I can use both in my code.
I'm struggling to figure out a way to find the last element in the string in order to extract it, in Smalltalk.
You didn't told which incarnation of Smalltalk you use, so I will explain what I would do in Pharo, that is the one I'm familiar with.
As someone that is playing with Pharo a few months at most, I can tell you the sheer amount of classes and methods available can feel overpowering at first, but the environment actually makes easy to find things. For example, when you know the exact input and output you want, but doesn't know if a method already exists somewhere, or its name, the Finder actually allow you to search by giving a example. You can open it in the world menu, as shown bellow:
By default it seeks selectors (method names) matching your input terms:
But this default is not what we need right now, so you must change the option in the upper right box to "Examples", and type in the search field a example of the input, followed by the output you want, both separated by a ".". The input example I used was the string 'max6', followed by the desired result, the number 6. Pharo then gives me a list of methods that match that:
To get what would return us the text part, you can make a new search, changing the example output from number 6 to the string 'max':
Fortunately there is several built-in methods matching the description of your problem.
There are more elegant ways, I suppose, but you can make use of the fact that String>>#asNumber only parses the part it can recognize. So you can do
'print31' reversed asNumber asString reversed asNumber
to give you 31. That only works if there actually is a number at the end.
This is one of those cases where we can presume the input data has a specific form, ie, the only numbers appear at the end of the string, and you want all those numbers. In that case it's not too hard to do, really, just:
numText := 'Kalahari78' select: [ :each | each isDigit ].
num := numText asInteger. "78"
To get the rest of the string without the digits, you can just use this:
'Kalahari78' withoutTrailingDigits. "Kalahari"6
As some of the Pharo "OGs" pointed out, you can take a look at the String class (just type CMD-Return, type in String, hit Return) and you will find an amazing number of methods for all kinds of things. Usually you can get some ideas from those. But then there are times when you really just need an answer!
In TI-BASIC, the + operation is overloaded for string concatenation (in this, if nothing else, TI-BASIC joins the rest of the world).
However, any attempt to concatenate involving an empty string raises a Dimension Mismatch error:
"Fizz"+"Buzz"
FizzBuzz
"Fizz"+""
Error
""+"Buzz"
Error
""+""
Error
Why does this occur, and is there an elegant workaround? I've been using a starting space and truncating the string when necessary (doesn't always work well) or using a loop to add characters one at a time (slow).
The best way depends on what you are doing.
If you have a string (in this case, Str1) that you need to concatenate with another (Str2), and you don't know if it is empty, then this is a good general-case solution:
Str2
If length(Str1
Str1+Str2
If you need to loop and add a stuff to the string each time, then this is your best solution:
Before the loop:
" →Str1
In the loop:
Str1+<stuff_that_isn't_an_empty_string>→Str1
After the loop:
sub(Str1,2,length(Str1)-1→Str1
There are other situations, too, and if you have a specific situation, then you should post a simplified version of the relevant code.
Hope this helps!
It is very unfortunate that TI-Basic doesn't support empty strings. If you are starting with an empty string and adding chars, you have to do something like this:
"?
For(I,1,3
Prompt Str1
Ans+Str1
End
sub(Ans,2,length(Ans)-1
Another useful trick is that if you have a string that you are eventually going to evaluate using expr(, you can do "("+Str1+")"→Str1 and then freely do search and replace on the string. This is a necessary workaround since you can't search and replace any text involving the first or last character in a string.
I want to remove all the characters from a string expect whatever character is between a certain set of characters. So for example I have the input of Grade:2/2014-2015 and I want the output of just the grade, 2.
I'm thinking that I need to use the FIND function to grab whatever is between the : and the / , this also needs to work with double characters such 10 however I believe that it would work so long as the defining values with the FIND function are correct.
Unfortunately I am totally lost on this when using the FIND function however if there is another function that would work better I could probably figure it out myself if I knew what function.
It's not particularly elegant but =MID(A1,FIND(":",A1)+1,FIND("/",A1) - FIND(":",A1) - 1) would work.
MID takes start and length,FIND returns the index of a given character.
Edit:
As pointed out, "Grade:" is fixed length so the following would work just as well:
=MID(A1,7,FIND("/",A1) - 7)
You could use LEFT() to remove "Grade:"
And then use and then use LEFTB() to remove the year.
Look at this link here. This is the way I would go about it.
=SUBSTITUTE(SUBSTITUTE(C4, "Grade:", ""), "/2014-2015", "")
where C4 is the name of your cell.
I just wrote a code with the criteria above, but it doesn't seem to work properly because I either miss a letter at the end or in the middle.
Could anyone please check out my code an tell me what I'm doing wrong. By the way I already checked other threads on this similar problem, but I'm not allowed to use regex or print function.
phrase=('my room is cold')
allSpaces=findstr(' ',phrase);
k=length(allSpaces)
acr=phrase(1:allSpaces(1):allSpaces(k)-1)
Output:
acr= mrms
Change last line to
acr = phrase([1 allSpaces+1])
That way you get the first letter, and then the first after each space.
I'm reading from ASCII data files with text headers. (The headers contain info about the data run.) I want to add some of the columns of each data file, then write the result to another data file, but keep the headers for each of the files. The problem is, I don't know beforehand what the lengths of the header lines are. If I use a long character variable (character*400, for example) to make sure I get the entire header lines, then my new data files have lots of white space I don't want. Basically, I want to do TRIM(HeaderVariable), but TRIM is not available to me. Any suggestions? Is there a way to WRITE only to a CrLF? I thought of using an array of character*1, and testing each character as I read it and write it, but...wow, that's sooooo complicated. Is there a simpler way to do this in standard F77?
[edit: self-answer moved to answer. could not do it at first because rep was too low.]
I got the answer. Posting here to help others. The LENGTH function below is taken from http://www.star.le.ac.uk/~cgp/prof77.html#tth_sEc7 Once you've got this LENGTH function, it's trivial to implement your own TRIM function. Functionally, this isn't much different from my initial horrid idea, but it's prettier.
LEN The LEN function takes a character argument and returns its length as an integer. The argument may be a local character variable or array element but this will just return a constant. LEN is more useful in procedures where character dummy arguments (and character function names) may have their length passed over from the calling unit, so that the length may be different on each procedure call. The length returned by LEN is that declared for the item. Sometimes it is more useful to find the length excluding trailing blanks. The next function does just that, using LEN in the process.
INTEGER FUNCTION LENGTH(STRING) !Returns length of string ignoring trailing blanks
CHARACTER*(*) STRING
DO 15, I = LEN(STRING), 1, -1
IF(STRING(I:I) .NE. ' ') GO TO 20
15 CONTINUE
20 LENGTH = I
END