1. carding second chapter, understand and write a summary.
First, the definition
A sign language system, including syntax and semantics; main component is a grammar rule (production), we can generate the syntax tree is derived by a rule.
Second, the grammar G four-tuple (V N, V T , P, S)
V N non-terminal symbol set
V T is set terminator
P rule (α → β) set
S is the start symbol identifiers or at least to appear as the left portion in a rule.
Third, the type of grammar
Grammar discrimination tips
Fourth, the syntax tree and ambiguity tree
Syntax Tree: also known as parse tree for the sentence to derive contextual description.
In the process of deriving α => β, it is necessary to follow the most left (right) derived, i.e., are on the leftmost (rightmost) of [alpha] nonterminal replaced. Rightmost derivation is also known as canonical derivation.
If there is a grammar of a sentence corresponding to two different syntax tree, then the grammar is ambiguous in. And the ambiguous grammar undecidable.
Note: ≠ grammar ambiguous language ambiguity
→ language is not ambiguous existence of a grammar is not ambiguous;
Grammar is not ambiguous can not be determined →
Comprehension and Summary: grammar and language learning is the main rule of grammar transformation and generate a corresponding spanning accordance with the guidelines followed in its transformation process can be used to verify the uniqueness of the guidelines.
2. Try to write grammar PL / 0 language.
Integer n
Grammar: <n> :: = <integer>
I identifier
文法：<i>::=<id>
Expression e
Grammar: <E>: = [+ | -] <item> {<subtraction operator> <term>}
<Item> :: = <factor> {<multiplication and division algorithms> <factor>}
<Subtraction operator> :: = + | -
Conditional statements
文法：<条件语句>::=if<条件>then<语句>
赋值语句
文法：<赋值语句>::=<id>:=<表达式>
复合语句
文法：<复合语句>::=begin<语句>{;<语句>} end
函数
文法：<函数>::=function <id>() :
<上述各种组合>
程序
文法：<程序>::=<分程序>.
...