編譯原理：詞法分析實(shí)驗(yàn)報(bào)告

編譯原理實(shí)驗(yàn)報(bào)告年級(jí)學(xué)號(hào)姓名成績(jī)專(zhuān)業(yè)實(shí)驗(yàn)地點(diǎn)指導(dǎo)教師實(shí)驗(yàn)項(xiàng)目C_minus語(yǔ)言詞法分析器的設(shè)計(jì)實(shí)驗(yàn)日期概述詞法分析程序完成打的是編譯第一階段的工作，它的主要任務(wù)是從左至右逐個(gè)字符的對(duì)源程序進(jìn)行掃描，產(chǎn)生一個(gè)個(gè)單詞序列，用以語(yǔ)法分析。本程序是獨(dú)立的一遍，把字符流的源程序變?yōu)閱卧~序列，輸出在一個(gè)中間文件上，這個(gè)文件作為語(yǔ)法分析程序的輸入而繼續(xù)編譯過(guò)程。正文詞法分析需解決的首要問(wèn)題是如何正確的獲得一個(gè)單詞，并判斷它的類(lèi)型，本程序設(shè)定了三種單詞類(lèi)型，分別為：關(guān)鍵字、標(biāo)識(shí)符、常數(shù)、運(yùn)算符和界符，其中，對(duì)標(biāo)識(shí)符和常數(shù)的判斷，用DFA圖，其余的直接定義成常量。下面逐一介紹：1、關(guān)鍵字（keyword）：elseifintreturnvoidwhile共6個(gè)，所有的關(guān)鍵字都是保留字，并且必須是小寫(xiě)。在程序中的定義為：#defineKEYWORD_ELSE1#defineKEYWORD_IF2#defineKEYWORD_INT3#defineKEYWORD_RETURN4#defineKEYWORD_VOID5#defineKEYWORD_WHILE6stringstrKey[6]={"else","if","int","return","void","while"};2、標(biāo)識(shí)符（Identifier）：識(shí)別與C語(yǔ)言詞法規(guī)定相一致的標(biāo)識(shí)符，通過(guò)下列正則表達(dá)式定義：ID=letter(letter|digit)*；所對(duì)應(yīng)的DFA圖如下：相應(yīng)的表示其類(lèi)型的定義為：#defineIDENTIFIER10對(duì)應(yīng)的判斷代碼為：boolIdentifier(charch[],intstate){ switch(state) { case0: if(isalpha(ch[0])) returnIdentifier(ch+1,1); else returnfalse; case1: if(isalpha(ch[0])||isdigit(ch[0])) returnIdentifier(ch+1,1); if(ch[0]=='\0') returntrue; else returnfalse; }}3、常數(shù)（constant）：NUM=(+|-|ε)digitdigit*(.digitdigit*|ε)(e(+|-|ε)digitdigit*|ε)，letter=a|..|z|A|..|Z|，digit=0|..|9，包括整數(shù)，如123,-123,+123等；小數(shù)，如123.45,+123.45,-123.45；科學(xué)計(jì)數(shù)法表示的常數(shù)，如+1.23e3，-2.3e-9；對(duì)應(yīng)的DFA圖如下：相應(yīng)的表示其類(lèi)型的定義：#defineCONSTANT_INTEGER20//整數(shù)#defineCONSTANT_DECIMAL21//小數(shù)#defineCONSTANT_SCIENTIFIC22//科學(xué)計(jì)數(shù)對(duì)應(yīng)的判斷代碼為：intConstant(charch[],intstate){ switch(state) { case0: if((ch[0]=='+')||(ch[0]=='-')) returnConstant(ch+1,1); elseif(isdigit(ch[0])) returnConstant(ch+1,2); else return0; case1: if(isdigit(ch[0])) returnConstant(ch+1,2); return0; case2: if(isdigit(ch[0])) returnConstant(ch+1,3); elseif((ch[0]=='.')&&isdigit(ch[1])) returnConstant(ch+2,4); elseif(ch[0]=='e') returnConstant(ch+1,5); elseif(ch[0]=='\0') returnCONSTANT_INTEGER; return0; case3: if(isdigit(ch[0])) returnConstant(ch+1,3); elseif(ch[0]=='e') returnConstant(ch+1,5); elseif((ch[0]=='.')&&isdigit(ch[1])) returnConstant(ch+2,4); elseif(ch[0]=='\0') returnCONSTANT_INTEGER; return0; case4: if(isdigit(ch[0])) returnConstant(ch+1,6); elseif(ch[0]=='e') returnConstant(ch+1,5); elseif(ch[0]=='\0') returnCONSTANT_DECIMAL; return0; case5: if(isdigit(ch[0])) returnConstant(ch+1,8); elseif((ch[0]=='+')||(ch[0]=='-')) returnConstant(ch+1,7); elseif(ch[0]=='\0')//認(rèn)為1.25e也為科學(xué)計(jì)數(shù)法 returnCONSTANT_SCIENTIFIC; return0; case6: if(ch[0]=='e') returnConstant(ch+1,5); elseif(isdigit(ch[0])) returnConstant(ch+1,6); elseif(ch[0]=='\0') returnCONSTANT_DECIMAL; return0; case7: if(isdigit(ch[0])) returnConstant(ch+1,8); elseif(ch[0]=='\0')//認(rèn)為1.25e+為錯(cuò)誤輸入 return0; return0; case8: if(isdigit(ch[0])) returnConstant(ch+1,8); elseif(ch[0]=='\0') returnCONSTANT_SCIENTIFIC; return0; } return0;}4、運(yùn)算符包括：+、-、*、/、<=、<、>、=>、!=、==、=，程序中的定義如下：#defineSYMBOL_OPER_GREATER37//大于#defineSYMBOL_OPER_GREATER_EQUAL36//大于等于#defineSYMBOL_OPER_LESS35//小于#defineSYMBOL_OPER_LESS_EQUAL34//小于等于#defineSYMBOL_OPER_EQUAL_EQUAL39//等于#defineSYMBOL_OPER_NOT_EQUAL38//不等于#defineSYMBOL_OPER_EQUAL40//賦值號(hào)#defineSYMBOL_OPER_PLUS30//加法#defineSYMBOL_OPER_MINUS31//減法#defineSYMBOL_OPER_MULTIPLY32//乘號(hào)#defineSYMBOL_OPER_DIVISION33//除號(hào)stringstrOper[11]={"+","-","*","/","<=","<",">=",">","!=","==","="};5、界符包括：;、,、(、")、[、]、{、}、/*、*/，程序中的定義如下：#defineSYMBOL_BOUND_SEMICOLON50//分號(hào)#defineSYMBOL_BOUND_COMMA51//逗號(hào)#defineSYMBOL_BOUND_SMLBRA_LEFT52//左小括號(hào)#defineSYMBOL_BOUND_SMLBRA_RIGHT53//右小括號(hào)#defineSYMBOL_BOUND_SQUBAR_LEFT54//左中括號(hào)#defineSYMBOL_BOUND_SQUBAR_RIGHT55//右中括號(hào)#defineSYMBOL_BOUND_CURBAR_LEFT56//左大括號(hào)#defineSYMBOL_BOUND_CURBAR_RIGHT57//