Design mode 23: Interpreter mode

Interpreter mode:
Given a language, a representation of its grammar is defined, and an interpreter is defined that uses that representation to interpret the sentences in the language.
Given a language, define a representation for it grammar along with an interpreter that uses the representation to INTERP RET sentences in the language.

UML diagram:

Mainly include:

1. Abstractexpression: Declares an interface for performing an operation.
2. Terminalexpression: Terminator expression that implements the operation associated with Terminator in the grammar.
3. Nonterminalexpression: Non-terminator expression, the interpretation operation is implemented for the Terminator of Grammar. For every rule in grammar r1,r2,r3 ... a specific non-Terminator expression class is required.
4. Context: Contains some global information outside the interpreter.
5. Client: Defines an abstract syntax tree that is used to represent specific sentences in a language. The syntax tree is composed of nonterminalexpression and terminalexpression.

C + + implementation:

#include <iostream>#include <list>using namespace STD;classcontext{};classabstractexpression{ Public:Virtual voidInterpret (Context * c) =0;};classTerminalexpression: Publicabstractexpression{ Public:voidInterpret (Context *c) {cout<<"Terminalexpression interpret"<<endl; }};classNonterminalexpression: Publicabstractexpression{ Public:voidInterpret (Context *c) {cout<<"Nonterminalexpression interpret"<<endl; }};intMain () {cout<<"Interpreter mode Code"<<endl; list<abstractexpression *>Lists Context *c=NewContext; Abstractexpression * te1=NewTerminalexpression ();    Lists.push_back (TE1); Abstractexpression * te2=NewTerminalexpression ();    Lists.push_back (TE2); Abstractexpression * te3=NewTerminalexpression ();    Lists.push_back (TE3); Abstractexpression * te4=NewTerminalexpression ();    Lists.push_back (TE4); Abstractexpression * nte1=NewNonterminalexpression (); Lists.push_back (NTE1); list<AbstractExpression*>:: Iterator Iter=lists.begin (); for(; Iter!=lists.end (); iter++)    {(*iter)->interpret (c); }DeleteCDeleteTE1;DeleteRetDeleteTe3;DeleteTe4;Deletente1;return 0;}

Execution output:

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Design mode 23: Interpreter mode