Recursion (left recursion) | Compiler design

Recursion (left recursion) | Compiler design

• 1.
  Recursion
• 2.
  Index Definition for Recursion Classificationof Recursion About Left Recursion Elimination of Left Recursion and Example
• 3.
  Definition • Recursion isthe process a procedure goes through when one of the steps of the procedure involves invoking the procedure itself
• 4.
  Classification Recursion Left recursion Rightrecursion
• 5.
  Left Recursion A→A𝛼/𝛽 A A A A 𝛼 𝛼 𝛼 𝛽 A 𝛽 Top downparser doesn’t allow in Left Recursion bcz of it’s infinite problem. So… we need to eliminate this problem. Infinite problem
• 6.
  Elimination of LeftRecursion A→A𝛼/𝛽 A A A A 𝛼 𝛼 𝛼 𝛽 A 𝛽 𝛽 𝛼*
• 7.
  Elimination of LeftRecursion 𝐴 → 𝛽 𝛼* 𝐴 → 𝛽𝐴′ 𝐴′ → 𝛼𝐴′ /∈ 𝐴 → 𝛽𝐴′ 𝐴′ → 𝛼𝐴′ /∈ A→A𝛼/𝛽
• 8.
  Example E →E +T/ T 𝐴 → 𝛽𝐴′ 𝐴′ → 𝛼𝐴′ /∈ A→A𝛼/𝛽 A A 𝛼 𝛽 E→ 𝑇𝐸′ 𝐸′ → +𝑇 𝐸′ /∈
• 9.
  Thanks for yourattention! Any Question??...