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POerror in coding a lexer in c
 

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  1. POerror in coding a lexer in c
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    <pre><code>#include&lt;stdio.h&gt; #include&lt;ctype.h&gt; #include&lt;string.h&gt; /* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */ int main() { int i=0,j,k,count=0; char a,b[100],c[10000],d[100]; memset ( d, 0, 100 ); j=30; FILE *fp1,*fp2; fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer fp2=fopen("lext.txt","w"); //now lets remove all the white spaces and store the rest of the words in a file if(fp1==NULL) { perror("failed to open source.txt"); //return EXIT_FAILURE; } i=0; k=0; while(!feof(fp1)) { a=fgetc(fp1); if(a!=' '&amp;&amp;a!='\n') { if (!isalpha(a)) { switch(a) { case '+':{fprintf(fp2,"+ ----&gt; PLUS \n"); i=0;break;} case '-':{fprintf(fp2,"- ---&gt; MINUS \n"); i=0;break;} case '*':{fprintf(fp2, "* ---&gt;MULT \n"); i=0;break;} case '/':{fprintf(fp2, "/ ---&gt;DIV \n"); i=0;break;} //case '+=':fprintf(fp2, "%.20s\n", "ADD_ASSIGN"); //case '-=':fprintf(fp2, "%.20s\n", "SUB_ASSIGN"); case '=':{fprintf(fp2, "= ---&gt; ASSIGN \n"); i=0;break;} case '%':{fprintf(fp2, "% ---&gt; MOD \n"); i=0;break;} case '&lt;':{fprintf(fp2, "&lt; ---&gt; LESSER_THAN \n"); i=0;break;} case '&gt;':{fprintf(fp2, "&gt; --&gt; GREATER_THAN \n"); i=0;break;} //case '++':fprintf(fp2, "%.20s\n", "INCREMENT"); //case '--':fprintf(fp2, "%.20s\n", "DECREMENT"); //case '==':fprintf(fp2, "%.20s\n", "ASSIGNMENT"); case ';':{fprintf(fp2, "; ---&gt;SEMI_COLUMN \n"); i=0;break;} case ':':{fprintf(fp2, ": ---&gt;COLUMN \n"); i=0;break;} case '(':{fprintf(fp2, "( ---&gt;LPAR \n"); i=0;break;} case ')':{fprintf(fp2, ") ---&gt;RPAR \n"); i=0;break;} case '{':{fprintf(fp2, "{ ---&gt;LBRACE \n"); i=0;break;} case '}':{fprintf(fp2, "} ---&gt; RBRACE \n"); i=0;break;} } } else { d[i]=a; //printf("%c\n",d[i]); i=i+1; } //} /* we can make the lexer more complex by including even more depths of checks for the symbols*/ } else { d[i+1]='\0'; printf("\n"); if((strcmp(d,"if ")==0)){fprintf(fp2,"if ----&gt; IDENTIFIER \n"); //printf("%s \n",d); memset ( d, 0, 100 ); //printf("%s \n",d); count=count+1;} else if(strcmp(d,"then")==0){fprintf(fp2,"then ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"else")==0){fprintf(fp2,"else ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"switch")==0){fprintf(fp2,"switch ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"printf")==0){fprintf(fp2,"prtintf ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"scanf")==0){fprintf(fp2,"scanf ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"NULL")==0){fprintf(fp2,"NULL ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"int")==0){fprintf(fp2,"INT ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"char")==0){fprintf(fp2,"char ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"float")==0){fprintf(fp2,"float ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"long")==0){fprintf(fp2,"long ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"double")==0){fprintf(fp2,"double ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"const")==0){fprintf(fp2,"const ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"continue")==0)fprintf(fp2,"continue ----&gt; IDENTIFIER \n"); else if(strcmp(d,"size of")==0){fprintf(fp2,"size of ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"register")==0){fprintf(fp2,"register ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"short")==0){fprintf(fp2,"short ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"auto")==0){fprintf(fp2,"auto ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"while")==0){fprintf(fp2,"while ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"do")==0){fprintf(fp2,"do ----&gt; IDENTIFIER \n"); count=count+1;} else if(strcmp(d,"case")==0){fprintf(fp2,"case ----&gt; IDENTIFIER \n"); count=count+1;} else if (isdigit(d[i])) { fprintf(fp2,"%s ----&gt;NUMBER",d); } else if (isalpha(a)) { fprintf(fp2,"%s ----&gt; Variable",d); //printf("%s",d); // memset ( d, 0, 100 );} //fprintf(fp2, "s\n", b); i=0; k=k+1; continue; } i=i+1; k=k+1; } fclose(fp1); fclose(fp2); printf("%d",count); return 0; } </code></pre> <p>In this code , my source.txt has if (a+b) stored . But only ( , + and ) is getting written into lext.txt and not the identifier if or the variable a and b . Any particular reason why?</p>
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    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USPeter Lang
    1. USHick
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
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      1. PTAnswer
    2. PO
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      1. PTAnswer
    3. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. COA helpful hint: C allows you to name your variables with identifiers longer than a single character.
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      1. POerror in coding a lexer in c
      1. USJames McNellis
    2. COBecause your code has errors.
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      1. POerror in coding a lexer in c
      1. USqrdl
    3. CONext time **indent** your code and **delete unwanted empty** lines. That makes it easy for us to analyze your code.
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      1. POerror in coding a lexer in c
      1. UScodaddict
 

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