Editing Left recursion (section)

== Uses ==
Left recursion is commonly used as an idiom for making operations [[left-associative]]: that an expression <code>a+b-c-d+e</code> is evaluated as <code>(((a+b)-c)-d)+e</code>. In this case, that evaluation order could be achieved as a matter of syntax via the three grammatical rules
:<math> \mathit{Expression} \to \mathit{Term} </math>
:<math> \mathit{Expression} \to \mathit{Expression} + \mathit{Term} </math>
:<math> \mathit{Expression} \to \mathit{Expression} - \mathit{Term} </math>
These only allow parsing the <math>\mathit{Expression}</math> <code>a+b-c-d+e</code> as consisting of the <math>\mathit{Expression}</math> <code>a+b-c-d</code> and <math>\mathit{Term}</math> <code>e</code>, where <code>a+b-c-d</code> in turn consists of the <math>\mathit{Expression}</math> <code>a+b-c</code> and <math>\mathit{Term}</math> <code>d</code>, while <code>a+b-c</code> consists of the <math>\mathit{Expression}</math> <code>a+b</code> and <math>\mathit{Term}</math> <code>c</code>, etc.