I saw this code en Tcl:
entry .amount -validate key -validatecommand {
expr {[string is int %P] || [string length %P]==0}
}
I know that it's an entry validation but, what does "%P" in that code? I was looking in the Tcl's doc but I didn't find nothing.
I think this is another way to do it but it has the same symbols:
proc check_the_input_only_allows_digits_only {P} {
expr {[string is int P] || [string length P] == 0}
}
entry .amount \
-validate key \
-validatecommand {check_the_input_only_allows_digits_only %P}
The tcl-tk page for entry says
%P
The value of the entry if the edit is allowed. If you are configuring the entry widget to have a new textvariable, this will be the value of that textvariable.