SNL文法的递归下降语法分析器

得到token序列后，我们就可以采用递归下降法对其进行语法分析。如果没有语法错误，打印token序列,提示没有语法错误,否则，打印已经匹配的token，提示语法错误。（下面程序使用vs2013编译）

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <string>
#include <vector>using namespace std;//token结构体
struct Token
{Token(string str, int pos){this->type = str;this->pos = pos;}string type;int pos;
};vector<string> IdTable;//全局变量,标示符表
vector<int> NbTable;//全局变量,INTC值表
FILE *g_pf;//全局变量,打开*.token的文件指针
FILE *g_pf_log;//全局变量,日志文件*.log的文件指针vector<string> result;//记录匹配成功的token
int max_read_num = 0;//最大匹配token数量//从文件中读入一个token,需要先打开*.token文件
Token *ReadToken(FILE *pf)
{if (pf == NULL)exit(-1);char buf1[256] = { 0 };char buf2[256] = { 0 };int num = 0;if (!pf)return NULL;while (!feof(pf)){memset(buf1, 0, sizeof(buf1));memset(buf2, 0, sizeof(buf2));fgets(buf1, sizeof(buf1), pf);result.push_back(buf1);if (result.size() > max_read_num)//记录读入token数量最大值max_read_num = result.size();if (g_pf_log)fprintf(g_pf_log,"读入%s\n", buf1);sscanf(buf1, "(%[^,],%[^)]", buf1, buf2);if (buf2[0] == '"'){return new Token(buf1, -1);}else if (buf2[0] == '['){sscanf(buf2, "[%[0-9]", buf2);num = atoi(buf2);return new Token(buf1, num);}else{return NULL;}}return NULL;
}
//从文件流中回退一个token，需要先打开*.token文件
void BackToken(FILE*pf)
{if (pf == NULL)exit(-1);string tmp = result[result.size() - 1];int i = tmp.size();while (i){ungetc(tmp[--i], pf);}if (g_pf_log)fprintf(g_pf_log, "返回%s\n", result[result.size() - 1].c_str());result.erase(result.end() - 1);
}//总程序
bool MatchProgramHead();
bool MatchDeclarePart();
bool MatchProgramBody();
bool MatchProgramName();
bool MatchTypeDecpart();
bool MatchVarDecpart();
bool MatchProcDecpart();
bool MatchTypeDec();
bool MatchTypeDecList();
bool MatchTypeDecMore();
bool MatchTypeId();
bool MatchTypeName();
bool MatchBaseName();
bool MatchStructureType();
bool MatchArrayType();
bool MatchLow();
bool MatchTop();
bool MatchRecType();
bool MatchFieldDecList();
bool MatchFieldDecMore();
bool MatchIdList();
bool MatchIdMore();
//变量声明
bool MatchVarDecpart();
bool MatchVarDec();
bool MatchVarDecList();
bool MatchVarDecMore();
bool MatchVarIdList();
bool MatchVarIdMore();
//过程声明
bool MatchProcDecpart();
bool MatchProcDec();
bool MatchProcDecMore();
bool MatchProcName();
//参数声明
bool MatchParamList();
bool MatchParamDecList();
bool MatchParamMore();
bool MatchParam();
bool MatchFormList();
bool MatchFidMore();
//过程中的声明
bool MatchProcDecPart();
//过程体
bool MatchProcBody();
bool MatchProgramBody();
//语句序列
bool MatchStmList();
bool MatchStmMore();
//语句
bool MatchStm();
bool MatchAssCall();
bool MatchAssignmentRest();
bool MatchConditionalStm();
bool MatchLoopStm();
bool MatchInputStm();
bool MatchInvar();
bool MatchOutputStm();
bool MatchReturnStm();
bool MatchCallStmRest();
bool MatchActParamList();
bool MatchActParamMore();
bool MatchRelExp();
bool MatchOtherRelE();
bool MatchExp();
bool MatchOtherTerm();
bool MatchTerm();
bool MatchOtherFactor();
bool MatchFactor();
bool MatchVariable();
bool MatchVariMore();
bool MatchFieldVar();
bool MatchFieldVarMore();
bool MatchCmpOp();
bool MatchAddOp();
bool MatchMultOp();bool MatchProgram()
{if (!MatchProgramHead())return false;if (!MatchDeclarePart())return false;if (!MatchProgramBody())return false;if (ReadToken(g_pf)->type != "$."){BackToken(g_pf);return false;}return true;
}
bool MatchProgramHead()
{if (ReadToken(g_pf)->type == "$program")return MatchProgramName();return false;
}
bool MatchProgramName()
{if (ReadToken(g_pf)->type == "$id")return true;return false;
}
bool MatchDeclarePart()
{if (!MatchTypeDecpart())return false;if (!MatchVarDecpart())return false;if (!MatchProcDecpart())return false;return true;
}bool MatchTypeDecpart()
{MatchTypeDec();return true;
}
bool MatchTypeDec()
{if (ReadToken(g_pf)->type != "$type"){BackToken(g_pf);return false;}else{if (!MatchTypeDecList()){BackToken(g_pf);return false;}else{return true;}}
}
bool MatchTypeDecList()
{if (!MatchTypeId())return false;if (ReadToken(g_pf)->type != "$="){BackToken(g_pf);return false;}if (!MatchTypeName()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$;"){BackToken(g_pf);BackToken(g_pf);return false;}return MatchTypeDecMore();
}
bool MatchTypeDecMore()
{MatchTypeDecList();return true;
}
bool MatchTypeId()
{if (ReadToken(g_pf)->type == "$id")return true;else{BackToken(g_pf);return false;}
}
bool MatchTypeName()
{if (MatchBaseName())return true;if (MatchStructureType())return true;if (ReadToken(g_pf)->type == "$id")return true;else{BackToken(g_pf);return false;}return false;
}
bool MatchBaseName()
{if (ReadToken(g_pf)->type == "$integer")return true;else{   BackToken(g_pf);}if (ReadToken(g_pf)->type == "$char")return true;else{BackToken(g_pf);}return false;
}
bool MatchStructureType()
{if (MatchArrayType())return true;if (MatchRecType())return true;return false;
}
bool MatchArrayType()
{if (ReadToken(g_pf)->type != "$array"){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$["){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchLow()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$."){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$."){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchTop()){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$]"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$of"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}return MatchBaseName();
}
bool MatchLow()
{if (ReadToken(g_pf)->type != "$INTC"){BackToken(g_pf);return false;}return true;
}
bool MatchTop()
{if (ReadToken(g_pf)->type != "$INTC"){BackToken(g_pf);return false;}return true;
}
bool MatchRecType()
{if (ReadToken(g_pf)->type != "$record"){BackToken(g_pf);return false;}if (!MatchFieldDecList()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$end"){BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchFieldDecList()
{if (MatchBaseName())if (MatchIdList())if (ReadToken(g_pf)->type == "$;"){if (MatchFieldDecMore())return true;}else{BackToken(g_pf);}if (MatchArrayType())if (MatchIdList())if (ReadToken(g_pf)->type == "$;"){if (MatchFieldDecMore())return true;}else{BackToken(g_pf);}return false;
}
bool MatchFieldDecMore()
{MatchFieldDecList();return true;
}
bool MatchIdList()
{if (ReadToken(g_pf)->type != "$id"){BackToken(g_pf);return false;}       return MatchIdMore();
}
bool MatchIdMore()
{if (ReadToken(g_pf)->type == "$comma")if (MatchIdList()){return true;}else{BackToken(g_pf);}return true;
}bool MatchVarDecpart()
{MatchVarDec();return true;
}
bool MatchVarDec()
{if (ReadToken(g_pf)->type != "$var"){BackToken(g_pf);return false;}if (MatchVarDecList())return true;else{BackToken(g_pf);return false;}
}
bool MatchVarDecList()
{if (!MatchTypeName())return false;if (!MatchVarIdList())return false;if (ReadToken(g_pf)->type != "$;"){BackToken(g_pf);return false;}if (!MatchVarDecMore())return false;return true;
}
bool MatchVarDecMore()
{MatchVarDecList();return true;
}
bool MatchVarIdList()
{if (ReadToken(g_pf)->type != "$id"){BackToken(g_pf);return false;}if (!MatchVarIdMore())return false;return true;
}
bool MatchVarIdMore()
{if (ReadToken(g_pf)->type == "$comma"){if (MatchVarIdList()){return true;}else{BackToken(g_pf);}}else{BackToken(g_pf);}return true;
}//过程声明
bool MatchProcDecpart()
{MatchProcDec();return true;
}
bool MatchProcDec()
{if (ReadToken(g_pf)->type != "$procedure"){BackToken(g_pf);return false;}if (!MatchProcName()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$("){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchParamList()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$)"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$;"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchProcDecPart()){BackToken(g_pf);return false;}if (!MatchProcBody()){BackToken(g_pf);return false;}if (!MatchProcDecMore()){BackToken(g_pf);return false;}return true;
}
bool MatchProcDecMore()
{MatchProcDec();return true;
}
bool MatchProcName()
{if (ReadToken(g_pf)->type != "$id"){BackToken(g_pf);return false;}return true;
}
//参数声明
bool MatchParamList()
{MatchParamDecList();return true;
}
bool MatchParamDecList()
{if (!MatchParam())return false;if (!MatchParamMore())return false;return true;
}
bool MatchParamMore()
{if (ReadToken(g_pf)->type == "$;"){if (MatchParamDecList())return true;elseBackToken(g_pf);}else{BackToken(g_pf);}return true;
}
bool MatchParam()
{if (MatchTypeName())return MatchFormList();if (ReadToken(g_pf)->type == "$var"){if (MatchTypeName()){if (MatchFormList())return true;elseBackToken(g_pf);}else{BackToken(g_pf);}}else{BackToken(g_pf);}return false;
}
bool MatchFormList()
{if (ReadToken(g_pf)->type != "$id"){BackToken(g_pf);return false;}if(!MatchFidMore()){BackToken(g_pf);return false;}elsereturn true;
}
bool MatchFidMore()
{if (ReadToken(g_pf)->type == "$comma"){if (MatchFormList())return true;elseBackToken(g_pf);}else{BackToken(g_pf);}return true;
}
//过程中的声明
bool MatchProcDecPart()
{return MatchDeclarePart();
}
//过程体
bool MatchProcBody()
{return MatchProgramBody();
}
bool MatchProgramBody()
{if (ReadToken(g_pf)->type != "$begin"){BackToken(g_pf);return false;}if (!MatchStmList()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$end"){BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
//语句序列
bool MatchStmList()
{if (!MatchStm())return false;if (!MatchStmMore())return false;return true;
}
bool MatchStmMore()
{if (ReadToken(g_pf)->type == "$;"){if (MatchStmList())return true;else{BackToken(g_pf);return false;}}elseBackToken(g_pf);return true;
}
//语句
bool MatchStm()
{if (MatchConditionalStm())return true;if (MatchLoopStm())return true;if (MatchInputStm())return true;if (MatchOutputStm())return true;if (MatchReturnStm())return true;if (ReadToken(g_pf)->type == "$id")if (MatchAssCall())return true;elseBackToken(g_pf);elseBackToken(g_pf);return false;
}
bool MatchAssCall()
{if (MatchAssignmentRest())return true;if (MatchCallStmRest())return true;return false;
}
bool MatchAssignmentRest()
{if (!MatchVariMore())return false;if (ReadToken(g_pf)->type == "$:="){if (!MatchExp()){BackToken(g_pf);return false;}else{return true;}}else{BackToken(g_pf);return false;}
}
bool MatchConditionalStm()
{if (ReadToken(g_pf)->type != "$if"){BackToken(g_pf);return false;}if (!MatchRelExp()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$then"){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchStmList()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$else"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchStmList()){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$fi"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchLoopStm()
{if (ReadToken(g_pf)->type != "$while"){BackToken(g_pf);return false;}if (!MatchRelExp()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$do"){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchStmList()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$endwh"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchInputStm()
{if (ReadToken(g_pf)->type != "$read"){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$("){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchInvar()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$)"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchInvar()
{if (ReadToken(g_pf)->type != "$id"){BackToken(g_pf);return false;}return true;
}
bool MatchOutputStm()
{if (ReadToken(g_pf)->type != "$write"){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$("){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchExp()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$)"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchReturnStm()
{if (ReadToken(g_pf)->type != "$return"){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$("){BackToken(g_pf);BackToken(g_pf);return false;}if (!MatchExp()){BackToken(g_pf);BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$)"){BackToken(g_pf);BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchCallStmRest()
{if (ReadToken(g_pf)->type != "$("){BackToken(g_pf);return false;}if (!MatchActParamList()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$)"){BackToken(g_pf);BackToken(g_pf);return false;}return true;
}
bool MatchActParamList()
{if (!MatchExp())return MatchActParamMore();return true;
}
bool MatchActParamMore()
{if (ReadToken(g_pf)->type == "$;"){if (MatchActParamList())return true;else{BackToken(g_pf);return false;}}elseBackToken(g_pf);return true;
}
bool MatchRelExp()
{if (!MatchExp())return false;if (!MatchOtherRelE())return false;return true;
}
bool MatchOtherRelE()
{if (!MatchCmpOp())return false;if (!MatchExp())return false;return true;
}
bool MatchExp()
{if (!MatchTerm())return false;if (!MatchOtherTerm())return false;return true;
}
bool MatchOtherTerm()
{if (MatchAddOp())return MatchExp();return true;
}
bool MatchTerm()
{if (!MatchFactor())return false;if (!MatchOtherFactor())return false;return true;
}
bool MatchOtherFactor()
{if (MatchMultOp())return MatchTerm();return true;
}
bool MatchFactor()
{if (ReadToken(g_pf)->type == "$("){if (MatchExp()){if(ReadToken(g_pf)->type == "$)")return true;else{BackToken(g_pf);BackToken(g_pf);return false;}}else{BackToken(g_pf);return false;}}else{BackToken(g_pf);}if (ReadToken(g_pf)->type == "$INTC")return true;else{BackToken(g_pf);}if (MatchVariable())return true;return false;}
bool MatchVariable()
{if (ReadToken(g_pf)->type != "$id"){BackToken(g_pf);return false;}return MatchVariMore();
}
bool MatchVariMore()
{bool flag = true;if (ReadToken(g_pf)->type == "$["){if (MatchExp()){if (ReadToken(g_pf)->type == "$]"){return true;}else{BackToken(g_pf);BackToken(g_pf);return false;}}else{BackToken(g_pf);return false;}}else{BackToken(g_pf);}if (ReadToken(g_pf)->type == "$.")if (MatchFieldVar())return true;else{BackToken(g_pf);return false;}else{BackToken(g_pf);}return true;
}
bool MatchFieldVar()
{if (ReadToken(g_pf)->type == "$id"){if (MatchFieldVarMore())return true;else{BackToken(g_pf);return false;}}else{BackToken(g_pf);return false;}
}
bool MatchFieldVarMore()
{if (ReadToken(g_pf)->type == "$["){if (!MatchExp()){BackToken(g_pf);return false;}if (ReadToken(g_pf)->type != "$]"){BackToken(g_pf);return false;}}else{BackToken(g_pf);}return true;
}
bool MatchCmpOp()
{if (ReadToken(g_pf)->type == "$<")return true;elseBackToken(g_pf);if (ReadToken(g_pf)->type == "$=")return true;elseBackToken(g_pf);return false;
}
bool MatchAddOp()
{if (ReadToken(g_pf)->type == "$+")return true;elseBackToken(g_pf);if (ReadToken(g_pf)->type == "$-")return true;elseBackToken(g_pf);return false;
}
bool MatchMultOp()
{if (ReadToken(g_pf)->type == "$*")return true;elseBackToken(g_pf);if (ReadToken(g_pf)->type == "$/")return true;elseBackToken(g_pf);return false;
}int main(int argc, char **argv)
{//设置源文件名string filename;if (argc >= 2)filename = argv[1];elsefilename = "snl.txt";//打开*.tokeng_pf = fopen((filename+".token").c_str(), "r"); //判断文件是否存在if (g_pf == NULL){printf("请先进行词法分析！\n");return -1;}//打开语法分析日志文件,语法分析程序调用过程中记录分析信息g_pf_log = fopen((filename + ".log").c_str(), "w+");//进行语法分析，没有语法错误返回true，否则返回falsebool re = MatchProgram();//最多匹配结果while (result.size() < max_read_num){ReadToken(g_pf);//读入一个token}//关闭文件*.tokenfclose(g_pf);//打开文件*.resultFILE * pfile = fopen((filename+".result").c_str(), "w+");    //打印result中除最后一个token之外的所有tokenfor (auto iter = result.begin(); iter != result.end() - 1; ++iter){printf(" 已匹配%s", iter->c_str());fprintf(pfile, "已匹配%s", iter->c_str());}if (re)//没有语法错误{//打印最后一个单词printf(" 已匹配%s", (result.end()-1)->c_str());fprintf(pfile, "已匹配%s", (result.end()-1)->c_str());//打印提示成功信息printf("语法分析完成，没有语法错误!\n");fprintf(pfile, "语法分析完成，没有语法错误!\n");}else//存在语法错误{//打印错误信息printf(" 语法错误：单词不匹配%s", (result.end()-1)->c_str());fprintf(pfile, "语法错误：单词不匹配%s", (result.end()-1)->c_str());}//关闭文件*.resultfclose(pfile);//暂停system("pause");
}

程序运行结果打印到屏幕，并写入到*.result文件

语法分析阶段完成，如果要写编译器，后面还需要有语义分析，中间代码生成等等。

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