Homemade programming language Note: Using YACC with Lex to make a simple calculator

1. Code

1.1) TEST.L

1.2) Test.y

1.3) Makefile (because it is in a Linux environment, so Makefile is used)

2. Compiling and Running

2.1) Compiling

2.2) Run

1, the code (also can be in my Baidu network disk download:http://pan.baidu.com/s/1o65k7v8)

1.1) Lex File test.l

1%{2#include <stdio.h>3#include"Y.tab.h"4 5 int 6Yywrap (void)7 {8     return 1;9 }Ten%} One%% A "+"    returnADD; - "-"    returnSUB; - "*"    returnMUL; the "/"    returnDIV; - "\ n"   returnCR; -([1-9][0-9]*)|0| ([0-9]+\. [0-9]*) { -     Doubletemp; +SSCANF (Yytext,"%LF", &temp); -Yylval.double_value =temp; +     returndouble_literal; A } at [\ t]; - . { -fprintf (stderr,"lexical error.\n"); -Exit1); - } -%%

1.2) YACC file Text.y

1%{2#include <stdio.h>3#include <stdlib.h>4 #defineYydebug 15%}6%Union {7     intInt_value;8     DoubleDouble_value;9 }Ten%token <double_value>double_literal One%token ADD SUB MUL DIV CR A%type <double_value>Expression Term primary_expression -%% - line_list the : Line -|line_list Line -     ; -  Line + : Expression CR -     {    +printf">>%lf\n>", $1); A fflush (stdout); at     }    - expression - : term -|expression ADD term -     { -$$ = $1+ $3; in     } -|expression SUB term to     { +$$ = $1- $3; -     } the     ; *  Term $ : Primary_expressionPanax Notoginseng|Term MUL primary_expression -     { the$$ = $1* $3; +     } A|Term DIV primary_expression the     { +$$ = $1/ $3; -     } $     ; $ primary_expression - : Double_literal -     ; the%% - intWuyiYyerror (Char*str) the { -     extern Char*Yytext; Wufprintf (stderr,"parser Error near%s\n", yytext); -     return 0; About } $  - intMainvoid) - { -     extern intYyparse (void); A     externFILE *Yyin; +  theprintf">"); - fflush (stdout); $Yyin =stdin; the     if(Yyparse ()) { thefprintf (stderr,"Error! Error! Error!\n"); theExit1); the     } -}

1.3) Makefile file (in fact, do not makefile, I am here in order to compile and purge each time when used, the following commands can be executed in three steps manually, the original is manually executed)

 1  . Phony:dummy  2  3  all:dummy  4  yacc-DV test.y   5   Lex Test.l  6   GCC -o test lex.yy.c y.tab.c   7  8  clean:dummy  9  rm -rf lex.yy.c test y.output y.tab.c y.tab.h  

2. Compiling and Running

2.1) Compiling

1  Make 2 YACC-dv test.y3Lex test.l4gcc -o test lex.yy.c Y.TAB.C

2.2) Run

1 ls 2 lex.yy.c  Makefile  readme.txt  test  test.l  test.y  y.output  y.tab.c  y.tab.h3 $./4123-4+2*3/ 7 5 >>3.8571436 > q7 lexical error.

Source: "Self-made programming language" chapter II

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Homemade programming language Note: Using YACC with Lex to make a simple calculator