Bison Syntax Error Unexpected Expecting $end
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Syntax Error Unexpected Expecting End Of Input
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Syntax Error Unexpected Tidentifier Expecting End
$undefined expecting $end error up vote 2 down vote favorite Hi I have started leaning Bison parser generator. I tried the following program. I compiled and running the program using MinGW on Window 7, with mintty client terminal. Bison version is 2.4.2 %verbose %error-verbose %{ #include
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Syntax Error Unexpected Keyword_ensure Expecting End
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Bison Syntax Error Unexpected Identifier
Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up How do I bison syntax error line number convince Bison to parse part of a file? up vote 2 down vote favorite If a have a input file of the form: BEGIN stuff.... END BEGIN stuff ... END and my .y file is of the form %token BEGIN %token END %start http://stackoverflow.com/questions/35686293/bison-syntax-error-unexpected-undefined-expecting-end-error begin begin: BEGIN stuff END and what I want to do is call yyparse repeatedly, parsing a single BEGIN/END, until eof. The first call to yyparse reports: syntax error, unexpected BEGIN, expecting $end. which makes sense; bison wants to parse the entire file. Is there a way to have bison be more flexible in it's defintion of $end? bison yacc share|improve this question asked Jul 19 '12 at 15:49 user1538392 212 add a comment| 2 Answers 2 active oldest votes up vote 3 down vote The http://stackoverflow.com/questions/11564563/how-do-i-convince-bison-to-parse-part-of-a-file easiest way is to add a (pair of) productions to the top of the .y file: input: begin | input begin; Now yyparse will parse multiple inputs. If your REALLY want to have to call yyparse multiple times, you could instead probably get away with: begin: BEGIN stuff END { YYACCEPT; } ; YYACCEPT is a special builtin that causes yyparse to return immediately with 0 (after doing any needed internal cleanup). I say "probably" as this will only work if bison reduces begin with a default reduction (no lookahead). That will be the case if this is the only rule for begin and begin is not used in a context where recognizing it requires lookahead. share|improve this answer answered Jul 19 '12 at 17:41 Chris Dodd 60.8k359118 I would prefer to call yyparse repeatedly; it makes more sense for this particular application. –user1538392 Jul 19 '12 at 18:09 I would prefer to call yyparse repeatedly; it makes more sense for this particular application. YYACCEPT returns immediately, not performing the semantic rule; I added "begin0: begin {YYACCEPT;} ;" to make it work. It now processes all of the blocks, and errors at the EOF. I need to add an empty rule to handle EOF, and I think that will make it work. Thank you. –user1538392 Jul 19 '12 at 18:15 Yes, adding a empty rule that sets the tree root pointer to null to signal the calling app that eof was reached seems to work. –user1538392 Jul 19 '12 at
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topics Evaluation software Community Events Search developerWorks developerWorksTechnical topicsLinuxTechnical library Better error handling using Flex and BisonTips for building more user-friendly compilers and interpreters Although it is easy to generate programs using Flex and Bison, it is a bit harder to make those programs produce user-friendly syntax and semantic error messages. This article examines the error-handling features of Flex and Bison, shows how to use them, and details some pitfalls. PDF (209 KB) | Share: Christian Hagen (chagen@de.ibm.com), Senior IT Architect, IBM Close [x] Christian Hagen is a Senior IT Architect with IBM Global Business Services, Application Services. Although he works as an IT architect, he likes to go back to the basics and do some programming. 28 July 2006 Also available inRussian Table of contents Introduction Sample source files Sample with plain error messages Extending Bison for better error messages A better input function Bison's location mechanism Conclusion Download Resources Comments IntroductionAs UNIX® developers know, Flex and Bison are powerful tools for developing lexical and grammar parsers, in particular language compilers and interpreters. If you're unfamiliar with these utilities or the tools they implement -- Lex and Yacc, respectively -- check the Resources section in this article for links to the Flex and Bison documentation and to additional articles that introduce both programs.This article covers a somewhat more advanced topic: features and techniques for putting better error-handling capabilities into your compiler or interpreter. To illustrate these techniques, I use a sample program called ccalc, which implements an enhanced calculator based on the infix calculator from the Bison handbook. You can download ccalc and associated files from the Download section at the end of this article.The enhancements include the use of variables. In ccalc, a variable is defined through its first use in an initialization such as a = 3. If a variable is used before it is initialized, a semantic error is generated, the variable is created with a value of zero, and a message is printed. Sample source filesThe sample source code consists of seven files: ccalc.c: The main program and some functions for input, output, and error processing ccalc.h:: Included definitions for all modules cmath.c: Mathematical functions parse.y: Input grammar for Bison lex.l Input for Flex makefile: A simple makefile defs.txt: Sample input file The prog