problem with flex output with decimal numbers
I am programming a small floating numbers calculator in Flex and Bison. So far my code is the following:
Flex code
%{
# include "prb1.tab.h"
float yylval;
%}
%%
"+" { return ADD; }
"-" { return SUB; }
"*" { return MUL; }
"/" { return DIV; }
"|" { return ABS; }
[0-9]+(.[0-9]+)? { yylval = atof(yytext); return NUMBER; }
n { return EOL; }
[ t] { /* ignore whitespace */ }
. { printf("Mystery character %cn", *yytext); }
%%
yywrap()
{
}
/*main(int argc, char **argv)
{
int tok;
while(tok = yylex()) {
printf("%d", tok);
if(tok == NUMBER) printf(" = %fn", yylval);
else printf("n");
}
}*/
Bison code
/* simplest version of calculator */
%{
#include <stdio.h>
%}
/* declare tokens */
%token NUMBER
%token ADD SUB MUL DIV ABS
%token EOL
%%
calclist: /* nothing */
| calclist exp EOL { printf("= %fn", $2); }
;
exp: factor
| exp ADD factor { $$ = $1 + $3; }
| exp SUB factor { $$ = $1 - $3; }
;
factor: term
| factor MUL term { $$ = $1 * $3; }
| factor DIV term { $$ = $1 / $3; }
;
term: NUMBER
| ABS term { $$ = $2 >= 0? $2 : - $2; }
;
%%
main(int argc, char **argv)
{
yyparse();
}
yyerror(char *s)
{
fprintf(stderr, "error: %sn", s);
}
The problem that I have is when I run the program the answer is still in integer. How can I change it to display the answer as a floating point number?
Thanks
bison flex-lexer
asked Nov 15 '18 at 14:59
LittleLittle
98352245
add a comment |
I am programming a small floating numbers calculator in Flex and Bison. So far my code is the following:
Flex code
%{
# include "prb1.tab.h"
float yylval;
%}
%%
"+" { return ADD; }
"-" { return SUB; }
"*" { return MUL; }
"/" { return DIV; }
"|" { return ABS; }
[0-9]+(.[0-9]+)? { yylval = atof(yytext); return NUMBER; }
n { return EOL; }
[ t] { /* ignore whitespace */ }
. { printf("Mystery character %cn", *yytext); }
%%
yywrap()
{
}
/*main(int argc, char **argv)
{
int tok;
while(tok = yylex()) {
printf("%d", tok);
if(tok == NUMBER) printf(" = %fn", yylval);
else printf("n");
}
}*/
Bison code
/* simplest version of calculator */
%{
#include <stdio.h>
%}
/* declare tokens */
%token NUMBER
%token ADD SUB MUL DIV ABS
%token EOL
%%
calclist: /* nothing */
| calclist exp EOL { printf("= %fn", $2); }
;
exp: factor
| exp ADD factor { $$ = $1 + $3; }
| exp SUB factor { $$ = $1 - $3; }
;
factor: term
| factor MUL term { $$ = $1 * $3; }
| factor DIV term { $$ = $1 / $3; }
;
term: NUMBER
| ABS term { $$ = $2 >= 0? $2 : - $2; }
;
%%
main(int argc, char **argv)
{
yyparse();
}
yyerror(char *s)
{
fprintf(stderr, "error: %sn", s);
}
The problem that I have is when I run the program the answer is still in integer. How can I change it to display the answer as a floating point number?
Thanks
bison flex-lexer
asked Nov 15 '18 at 14:59
LittleLittle
98352245
add a comment |
I am programming a small floating numbers calculator in Flex and Bison. So far my code is the following:
Flex code
%{
# include "prb1.tab.h"
float yylval;
%}
%%
"+" { return ADD; }
"-" { return SUB; }
"*" { return MUL; }
"/" { return DIV; }
"|" { return ABS; }
[0-9]+(.[0-9]+)? { yylval = atof(yytext); return NUMBER; }
n { return EOL; }
[ t] { /* ignore whitespace */ }
. { printf("Mystery character %cn", *yytext); }
%%
yywrap()
{
}
/*main(int argc, char **argv)
{
int tok;
while(tok = yylex()) {
printf("%d", tok);
if(tok == NUMBER) printf(" = %fn", yylval);
else printf("n");
}
}*/
Bison code
/* simplest version of calculator */
%{
#include <stdio.h>
%}
/* declare tokens */
%token NUMBER
%token ADD SUB MUL DIV ABS
%token EOL
%%
calclist: /* nothing */
| calclist exp EOL { printf("= %fn", $2); }
;
exp: factor
| exp ADD factor { $$ = $1 + $3; }
| exp SUB factor { $$ = $1 - $3; }
;
factor: term
| factor MUL term { $$ = $1 * $3; }
| factor DIV term { $$ = $1 / $3; }
;
term: NUMBER
| ABS term { $$ = $2 >= 0? $2 : - $2; }
;
%%
main(int argc, char **argv)
{
yyparse();
}
yyerror(char *s)
{
fprintf(stderr, "error: %sn", s);
}
The problem that I have is when I run the program the answer is still in integer. How can I change it to display the answer as a floating point number?
Thanks
bison flex-lexer
asked Nov 15 '18 at 14:59
LittleLittle
98352245
I am programming a small floating numbers calculator in Flex and Bison. So far my code is the following:
Flex code
%{
# include "prb1.tab.h"
float yylval;
%}
%%
"+" { return ADD; }
"-" { return SUB; }
"*" { return MUL; }
"/" { return DIV; }
"|" { return ABS; }
[0-9]+(.[0-9]+)? { yylval = atof(yytext); return NUMBER; }
n { return EOL; }
[ t] { /* ignore whitespace */ }
. { printf("Mystery character %cn", *yytext); }
%%
yywrap()
{
}
/*main(int argc, char **argv)
{
int tok;
while(tok = yylex()) {
printf("%d", tok);
if(tok == NUMBER) printf(" = %fn", yylval);
else printf("n");
}
}*/
Bison code
/* simplest version of calculator */
%{
#include <stdio.h>
%}
/* declare tokens */
%token NUMBER
%token ADD SUB MUL DIV ABS
%token EOL
%%
calclist: /* nothing */
| calclist exp EOL { printf("= %fn", $2); }
;
exp: factor
| exp ADD factor { $$ = $1 + $3; }
| exp SUB factor { $$ = $1 - $3; }
;
factor: term
| factor MUL term { $$ = $1 * $3; }
| factor DIV term { $$ = $1 / $3; }
;
term: NUMBER
| ABS term { $$ = $2 >= 0? $2 : - $2; }
;
%%
main(int argc, char **argv)
{
yyparse();
}
yyerror(char *s)
{
fprintf(stderr, "error: %sn", s);
}
The problem that I have is when I run the program the answer is still in integer. How can I change it to display the answer as a floating point number?
Thanks
bison flex-lexer
bison flex-lexer
asked Nov 15 '18 at 14:59
LittleLittle
98352245
asked Nov 15 '18 at 14:59
LittleLittle
98352245
asked Nov 15 '18 at 14:59
LittleLittle
98352245
asked Nov 15 '18 at 14:59
LittleLittle
98352245
asked Nov 15 '18 at 14:59
LittleLittle
98352245
98352245
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Unless you explicitly declare a semantic value type, bison/yacc assume that semantic values have type int. Declaring yylval in your flex file does not change anything, since bison never sees that file. (It leads to undefined behaviour, though, since yylval ends up being declared with two different types. I would gave expected the compiler ti complain about that.)
You can declare a semantic value type in your bison file like this:
%define api.value.type {double}
(I used double because it is almost certainly what you want; float is a low-precision datatype which should only be used if you have a good reason.)
You should also remove the declaration of yylval from your flex file, since it will be declared in the header file generated by bison.
See the bison manual for more details and code examples.
answered Nov 15 '18 at 17:25
ricirici
156k20135205
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
Anywhere in the declaration section. After%}and before%%. See bison manual for examples.
– rici
Nov 15 '18 at 18:20
@little: see above. Do not use the-yflag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.
– rici
Nov 15 '18 at 18:22
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53322217%2fproblem-with-flex-output-with-decimal-numbers%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Unless you explicitly declare a semantic value type, bison/yacc assume that semantic values have type int. Declaring yylval in your flex file does not change anything, since bison never sees that file. (It leads to undefined behaviour, though, since yylval ends up being declared with two different types. I would gave expected the compiler ti complain about that.)
You can declare a semantic value type in your bison file like this:
%define api.value.type {double}
(I used double because it is almost certainly what you want; float is a low-precision datatype which should only be used if you have a good reason.)
You should also remove the declaration of yylval from your flex file, since it will be declared in the header file generated by bison.
See the bison manual for more details and code examples.
answered Nov 15 '18 at 17:25
ricirici
156k20135205
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
Anywhere in the declaration section. After%}and before%%. See bison manual for examples.
– rici
Nov 15 '18 at 18:20
@little: see above. Do not use the-yflag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.
– rici
Nov 15 '18 at 18:22
add a comment |
Unless you explicitly declare a semantic value type, bison/yacc assume that semantic values have type int. Declaring yylval in your flex file does not change anything, since bison never sees that file. (It leads to undefined behaviour, though, since yylval ends up being declared with two different types. I would gave expected the compiler ti complain about that.)
You can declare a semantic value type in your bison file like this:
%define api.value.type {double}
(I used double because it is almost certainly what you want; float is a low-precision datatype which should only be used if you have a good reason.)
You should also remove the declaration of yylval from your flex file, since it will be declared in the header file generated by bison.
See the bison manual for more details and code examples.
answered Nov 15 '18 at 17:25
ricirici
156k20135205
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
Anywhere in the declaration section. After%}and before%%. See bison manual for examples.
– rici
Nov 15 '18 at 18:20
@little: see above. Do not use the-yflag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.
– rici
Nov 15 '18 at 18:22
add a comment |
Unless you explicitly declare a semantic value type, bison/yacc assume that semantic values have type int. Declaring yylval in your flex file does not change anything, since bison never sees that file. (It leads to undefined behaviour, though, since yylval ends up being declared with two different types. I would gave expected the compiler ti complain about that.)
You can declare a semantic value type in your bison file like this:
%define api.value.type {double}
(I used double because it is almost certainly what you want; float is a low-precision datatype which should only be used if you have a good reason.)
You should also remove the declaration of yylval from your flex file, since it will be declared in the header file generated by bison.
See the bison manual for more details and code examples.
answered Nov 15 '18 at 17:25
ricirici
156k20135205
Unless you explicitly declare a semantic value type, bison/yacc assume that semantic values have type int. Declaring yylval in your flex file does not change anything, since bison never sees that file. (It leads to undefined behaviour, though, since yylval ends up being declared with two different types. I would gave expected the compiler ti complain about that.)
You can declare a semantic value type in your bison file like this:
%define api.value.type {double}
(I used double because it is almost certainly what you want; float is a low-precision datatype which should only be used if you have a good reason.)
You should also remove the declaration of yylval from your flex file, since it will be declared in the header file generated by bison.
See the bison manual for more details and code examples.
answered Nov 15 '18 at 17:25
ricirici
156k20135205
answered Nov 15 '18 at 17:25
ricirici
156k20135205
answered Nov 15 '18 at 17:25
ricirici
156k20135205
answered Nov 15 '18 at 17:25
ricirici
156k20135205
156k20135205
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
Anywhere in the declaration section. After%}and before%%. See bison manual for examples.
– rici
Nov 15 '18 at 18:20
@little: see above. Do not use the-yflag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.
– rici
Nov 15 '18 at 18:22
add a comment |
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
Anywhere in the declaration section. After%}and before%%. See bison manual for examples.
– rici
Nov 15 '18 at 18:20
@little: see above. Do not use the-yflag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.
– rici
Nov 15 '18 at 18:22
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
thanks @rici, but in which part I should put the define.api.value? because I got the following error syntax.error, undefined {...}
– Little
Nov 15 '18 at 17:48
Anywhere in the declaration section. After
%} and before %%. See bison manual for examples.– rici
Nov 15 '18 at 18:20
Anywhere in the declaration section. After
%} and before %%. See bison manual for examples.– rici
Nov 15 '18 at 18:20
@little: see above. Do not use the
-y flag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.– rici
Nov 15 '18 at 18:22
@little: see above. Do not use the
-y flag when you invoke bison. If your bison version is very old, update it :-) or see the link in my answer for an alternative approach using a preprocessor macro.– rici
Nov 15 '18 at 18:22
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53322217%2fproblem-with-flex-output-with-decimal-numbers%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
