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Return to Grammar: Decidable and Undecidable Problems.
Grammar | <math>w \in L(G)</math> | <math>L(G) = \phi</math> | <math>L(G) = \Sigma^*</math> | <math>L(G_1) \subseteq L(G_2)</math> | <math>L(G_1) = L(G_2)</math> | <math>L(G_1) \cap L(G_2) = \phi</math> | <math>L(G) is finite</math> |
---|---|---|---|---|---|---|---|
Regular Grammar | D | D | D | D | D | D | D |
Det. Context Free | D | D | D | UD | ? | UD | D |
Context Free | D | D | UD | UD | UD | UD | D |
Context Sensitive | D | UD | UD | UD | UD | UD | UD |
Recursive | D | UD | UD | UD | UD | UD | UD |
Recursively Enumerable | D | UD | UD | UD | UD | UD | UD |
1.) the compliment of L(G1)\complement is a CFL
2.) L(G1) intersected with L(G2) is a CFL 3.) L(G1) = R
It is undecidable whether an arbitrary CFG is ambiguous
It is undecidable for arbitrary CFG's G1 and G2 whether L(G1) intersected with L(G2) is empty