As lanaer said, "<-" is really syntax sugar for ">>=" (bind), and could mean a variety of things (including assignment). "=" is binding a variable, as in "let",

As lanaer said, "<-" is really syntax sugar for ">>=" (bind), and could mean a variety of things (including assignment). "=" is binding a variable, as in "let", and is not symmetric. One could argue that a better name for "=" would be "->", as in "case". (Comparison, which is symmetric, is "==".)