In the formal language theory of computer science, left recursion is a special case of recursion.
In terms of context-free grammar, a non-terminal r is left-recursive if the left-most symbol in any of r’s ‘alternatives’ either immediately (direct left-recursive) or through some other non-terminal definitions (indirect/hidden left-recursive) rewrites to r again.
Read more about Left Recursion: Definition, Accommodating Left Recursion in Top-down Parsing, Pitfalls
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