C++ Compiler error when filtering a String field for backslash character

I'm trying to filter a field in a dataset for the backlsash character '\'

Based on my own thoughts and the docs I thought I should use:

myData(myColumn= '\\');

The documents state:
"To include the backslash character () in a constant string, use two backslashes (
) together."

Running this I can get different errors but of the same ilk - a C++ compiler isse

W20221202-123925 (Dev Thor) - using the playground with the latest compiler