Teknik Kompilasi TM 2 Kelompok

Q: Mengapa harus menghilangkan left recursive dan melakukan left factoring dalam top-down parsing?

A: Karena Recursive Descent Parser (salah satu top-down parser) tidak dapat menangani grammar left recursive.Ai??Hal ini disebabkan karena grammarAi??left recursiveAi??dapat menyebabkanAi??parserAi??men-backtrackAi??sampai akhirnya terjadiAi??infinite loopAi??(ketika suatu produksi yang bersifatAi??left recursiveAi??diAi??expand, maka akan mendapatkan variabel produksi yang sama sampai berulang kali atau tidak mencapai suatu terminal untuk mengambil keputusan). Maka dari itu, left recursive dari suatu produksi harus dihilangkan.

Left-factoringAi??merupakan cara merubah grammar yang bermanfaat untuk memproduksi grammar yang cocok untukAi??predictive, ataupunAi??top-down parsing.

Pada saat suatu grammar memiliki lebih dari satu produksi yang dapat men-expandAi?? nonterminal, atau yang disebut dengan ambigu, maka denganAi??Left factoringAi??kita dapat melakukan penulisan ulang produksi sampai produksi mendapatkan inputan yang sesuai untuk mengambil keputusanAi??(decision- making).

SebuahAi??predictive parserAi??(sebuahAi?? buy-viagra-through-paypal. top- down parserAi??tanpaAi??backtracking) mengharuskanAi??grammarAi??tersebut telah dilakukanAi??left factoring.

Sumber:

Aho, A.V., Lam, M.S.,Sethi, R., & Ullman, J.D. (2007). Compilers: Principles, Techniques and Tools. 2nd Edition.

http://asanisembiring.files.wordpress.com/2012/02/pertemuan-6.doc

http://www.cs.virginia.edu/~cs415/reading/RemovingLeftRecursion.pdf

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