I need to search for a substring in a string and return that if it is there in the string.
What is the best way to do that in Erlang? Note that i dont know the place that substring happens in the bigger string so i need to do a search for that.
You can use a regular expression:
> re:run("foobarbaz", "bar", [{capture, first, list}]).
{match,["bar"]}
See the documentation for re:run/3 for more information. In particular you may find that a different capture option suits your need.
Or if you don't need all the features of regular expressions, string:str/2 might be enough:
> string:str(" Hello Hello World World ", "Hello World").
8
This small function may help you. It returns true if the small string can be found in the big string, otherwise it returns false.
string_contains(Big, Small)->
string:str(Big, Small) > 0.
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!
I have a long string "AB100123485;AB10064279293-IP-1-KNPO;AB473898487-MM41". I have to extract integer value after "IP-" i.e 1 (only) what is the most efficient way ? I am using c#
Thanks
The 'most-efficient' way depends on how consistent your string is in terms of length and appearance. You can surely do this with a regular expression as a quick solution if you just want to get the digit directly following IP-.
You can utilize the RegularExpressions API, passing in your regular expression and input string.
https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.match?view=netframework-4.8#System_Text_RegularExpressions_Regex_Match_System_String_System_String_
This pattern should get you started IP-[0-9]; refine it more to your use case as needed.
For example:
Match matched = System.Text.RegularExpressions.Match(
"AB100123485;AB10064279293-IP-1-KNPO;AB473898487-MM41",
"IP-[0-9]"
);
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.
Hey guys so I tried looking at previous questions but they dont answer it like my teacher wants it to be answered. Basically i need to get a string from a user input and see if it has:
at least one of [!,#,#,$,%,^,&,*,(,)] (non-letter and nonnumeric
character)
o Create a list for these special characters
I have no idea how to make a def to do this. Please help!
You should probably look into Regular expressions. Regular expressions allow you to do many string operations in a concise way. Specifically, you'll want to use re.findall() in order to find all special characters in your string and return them. You can check if the returned list has length 0 to check if there were any special characters at all.
With regards to building the regular expression to find special characters itself... I'm sure you can figure that part out ;)
Please try the below
import re
inputstring = raw_input("Enter String: ")
print inputstring
print "Valid" if re.match("^[a-zA-Z0-9_]*$", inputstring) else "Invalid"
I have a huge string. I need to extract a substring from that that huge string. The conditions are the string starts with either "TECHNICAL" or "JUSTIFY" or "ALIGN" and ends with a number( any number from 1 to 10) followed by period and then followed by space. so for example, I have
string x = "This is a test, again I am testing TECHNICAL: I need to extract this substring starting with testing. 8. This is test again and again and again and again.";
so I need this
TECHNICAL: I need to extract this substring starting with testing.
I was wondering if someone has elegant solution for that.
I was trying to use the regular expression, but I guess I could not figure out the right expresion.
any help will be appreciated.
Thanks in advance.
Try this: #"((?:TECHNICAL|JUSTIFY|ALIGN).*?)(?:[1-9]|10)\. "