This is a follow-up question to LaTeX count number of occurrences of a character in a string
This works fine for printing the value. Now what I need is to check if this command returns a specific value. I'd like to do something like
if \CountSubStr{~}{This~is a ~test} = 0 then A else B.
Is it doable?
Here's a fairly general macro:
\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\countsubstringtestTF}{mmmmm}
{% #1 = substring to test for, #2 = string, #3 = test, #4 = true text, #5 = false text
\seq_set_split:Nnn \l__salys_substring_seq { #1 } { #2 }
\cs_set:Nn \__salys_substring_test:n
{
\int_compare:nTF { #3 } { #4 } { #5 }
}
\__salys_substring_test:n { \seq_count:N \l__salys_substring_seq - 1 }
}
\seq_new:N \l__salys_substring_seq
\ExplSyntaxOff
\begin{document}
\countsubstringtestTF{~}{This is a test}{#1>2}{greater than 2}{not greater than 2}
\countsubstringtestTF{~}{This~is a~test}{#1>2}{greater than 2}{not greater than 2}
\countsubstringtestTF{~}{This~is~a~test}{#1>2}{greater than 2}{not greater than 2}
\countsubstringtestTF{~}{This is a test}{1 <= #1 <= 2}{between 1 and 2}{not between 1 and 2}
\countsubstringtestTF{~}{This~is a~test}{1 <= #1 <= 2}{between 1 and 2}{not between 1 and 2}
\countsubstringtestTF{~}{This~is~a~test}{1 <= #1 <= 2}{between 1 and 2}{not between 1 and 2}
\end{document}
The number of matches is denoted, in the third argument, by #1; you can do several sorts of comparisons, like the ones shown here.
If you want to allow the second argument to be a control sequence, you can define a variant.
\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\countsubstringtestTF}{smmmmm}
{
\IfBooleanTF { #1 }
{
\salys_countsubstringtest:nVnTF #2 { #3 } { #4 } { #5 } { #6 }
}
{
\salys_countsubstringtest:nnnTF { #2 } { #3 } { #4 } { #5 } { #6 }
}
}
\cs_new_protected:Nn \salys_countsubstringtest:nnnTF
{% #1 = substring to test for, #2 = string, #3 = test, #4 = true text, #5 = false text
\seq_set_split:Nnn \l__salys_substring_seq { #1 } { #2 }
\cs_set:Nn \__salys_substring_test:n
{
\int_compare:nTF { #3 } { #4 } { #5 }
}
\__salys_substring_test:n { \seq_count:N \l__salys_substring_seq - 1 }
}
\seq_new:N \l__salys_substring_seq
\cs_generate_variant:Nn \salys_countsubstringtest:nnnTF { nV }
\ExplSyntaxOff
\newcommand{\mystringA}{This~is a~test}
\newcommand{\mystringB}{This~is~a~test}
\begin{document}
\countsubstringtestTF{~}{This is a test}{#1>2}{greater than 2}{not greater than 2}
\countsubstringtestTF*{~}{\mystringA}{#1>2}{greater than 2}{not greater than 2}
\countsubstringtestTF*{~}{\mystringB}{#1>2}{greater than 2}{not greater than 2}
\countsubstringtestTF{~}{This is a test}{1 <= #1 <= 2}{between 1 and 2}{not between 1 and 2}
\countsubstringtestTF{~}{This~is a~test}{1 <= #1 <= 2}{between 1 and 2}{not between 1 and 2}
\countsubstringtestTF{~}{This~is~a~test}{1 <= #1 <= 2}{between 1 and 2}{not between 1 and 2}
\end{document}
I don't really understand expl3, so may be better ways to do this. You can get this to work by adding by adding an \if_int_compare:w test to Werner's code:
\documentclass{article
\usepackage{xparse}
\ExplSyntaxOn
% \IfCountSubStrCompare{<substring>}{<string>}{=, < or >}{<int>}{<iftrue>}[<iffalse>]
\NewDocumentCommand{\IfCountSubStrCompare}{ m m m m m o }{
\seq_set_split:Nnn \l_tmpa_seq { #1 } { #2 }
\if_int_compare:w \int_eval:n {(\seq_count:N \l_tmpa_seq) - 1 } #3 #4
#5 % true code
\else
\IfValueT{#6}{#6}
\fi
}
\ExplSyntaxOff
\begin{document}
\IfCountSubStrCompare{~}{This~is a ~test}=0{Does not appear}[Appears]
\IfCountSubStrCompare{~}{This~is a ~test}=2{Appears twice}[Does not appear twice]
\IfCountSubStrCompare{~}{This~is a ~test}=3{Appears thrice}[Does not appear thrice]
\IfCountSubStrCompare{~}{This~is a ~test}>0{At least once }[Does not appear]
\IfCountSubStrCompare{~}{This~is a ~test}>1{More than once}[Once or less]
\IfCountSubStrCompare{~}{This~is a ~test}<2{Less than twice}[Twice or more]
\IfCountSubStrCompare{~}{This~is a ~test}<3{Less than thrice}[Thgrice or more]
\IfCountSubStrCompare{yes}{a yes b yes c yes deyesfg yehs ij}=4{Exactly four occurrences}
\end{document}
This produces the expected results:
The sytax of the \IfCountSubStrCompare command is:
\IfCountSubStrCompare{<substring>}{<string>}{=, < or >}{<int>}{<iftrue>}[<iffalse>]
So you need to give it a string to search for, a string to search in, a comparison operator (=, > or <), something to do if the comparison holds and, optionally, something to do if it doesn't.