“<-” breaks into “< -“

I have to blog R (https://www.r-project.org/) code occasionally and I found that wordpress have problem processing the “<-” (assign in R) no matter with or without the pre HTML tag. (using HTML mode) WP sometimes breaks “<-” into “< -” and render the code not “copy-and-paste” friendly. WP will break up “<-” even when the WP-syntax plugin is used.

I would like to know how to prevent it and I am using the blog.txt theme.

Thank you for your kind attention.