Handling exceptions with FParsec

up vote
1
down vote

favorite

I would like to be able to parse a file without the program launching an exception and stop the program at the first error. I use this:

let parse input = match run pprog input with
 | Success(result, _, _) -> result
 | Failure(msg, _, _) -> failwith msg

let program = parse myFile

The program variable is of the type AST.program (no need to show the implementation), thanks to the matching pattern of the parse function. If I do only this:

let program = run pprog myFile

program is of the type ParserResult<AST.Program, unit>, which is therefore unanalyzable.

I was wondering if there was a way not to crash the program with the exceptions launched?

asked Nov 10 at 12:16

Foxy

189110

How to not crash with an exception is easy: just use a try ... with block, and handle the exception in the with part. BUT... there's something you haven't mentioned in your question, which is: what do you want your program to do if FParsec parsing fails? How do you want your program to handle invalid input? Once you've decided the answer to that question, then all you need to do is to put that logic in the Failure branch of your parse function, instead of throwing an exception with failwith in that branch. So ask yourself this: what do you want to do with invalid input?
– rmunn
Nov 10 at 22:41

@rmunn – FParsec, during its parsing, already displays the errors. failwith launches an exception (which crashes the program on the way), but if I could avoid it it would be fine with me. Only, the parse function must be of the following type: string -> AST.Program. So I must necessarily return a data of the type AST.Program, or run an exception. But if there is a way to have a function of this type that does not launch an exception, I would be happy to know.
– Foxy
Nov 10 at 23:16

Does your AST.Program type have some kind of "empty" value? E.g., if it's a list of expressions, the "empty" value would be an empty list. If so, then your parse function could return the parsed program on success, and an empty program on failure.
– rmunn
2 days ago

@rmunn – I had thought about it at the beginning, and indeed there are no more exceptions, only it doesn't display errors, and stops the first time. What I'm actually looking for is a way to get an AST.Program data, and for all errors to be displayed without any exceptions. I also think that my way of doing things in the initial post is not correct in terms of what I would like to do in relation to the match. I looked at the documentation, but it doesn't deal with the subject.
– Foxy
yesterday

add a comment |

up vote
1
down vote

favorite

I would like to be able to parse a file without the program launching an exception and stop the program at the first error. I use this:

let parse input = match run pprog input with
 | Success(result, _, _) -> result
 | Failure(msg, _, _) -> failwith msg

let program = parse myFile

The program variable is of the type AST.program (no need to show the implementation), thanks to the matching pattern of the parse function. If I do only this:

let program = run pprog myFile

program is of the type ParserResult<AST.Program, unit>, which is therefore unanalyzable.

I was wondering if there was a way not to crash the program with the exceptions launched?

asked Nov 10 at 12:16

Foxy

189110

How to not crash with an exception is easy: just use a try ... with block, and handle the exception in the with part. BUT... there's something you haven't mentioned in your question, which is: what do you want your program to do if FParsec parsing fails? How do you want your program to handle invalid input? Once you've decided the answer to that question, then all you need to do is to put that logic in the Failure branch of your parse function, instead of throwing an exception with failwith in that branch. So ask yourself this: what do you want to do with invalid input?
– rmunn
Nov 10 at 22:41

@rmunn – FParsec, during its parsing, already displays the errors. failwith launches an exception (which crashes the program on the way), but if I could avoid it it would be fine with me. Only, the parse function must be of the following type: string -> AST.Program. So I must necessarily return a data of the type AST.Program, or run an exception. But if there is a way to have a function of this type that does not launch an exception, I would be happy to know.
– Foxy
Nov 10 at 23:16

Does your AST.Program type have some kind of "empty" value? E.g., if it's a list of expressions, the "empty" value would be an empty list. If so, then your parse function could return the parsed program on success, and an empty program on failure.
– rmunn
2 days ago

@rmunn – I had thought about it at the beginning, and indeed there are no more exceptions, only it doesn't display errors, and stops the first time. What I'm actually looking for is a way to get an AST.Program data, and for all errors to be displayed without any exceptions. I also think that my way of doing things in the initial post is not correct in terms of what I would like to do in relation to the match. I looked at the documentation, but it doesn't deal with the subject.
– Foxy
yesterday

add a comment |

up vote
1
down vote

favorite

I would like to be able to parse a file without the program launching an exception and stop the program at the first error. I use this:

let parse input = match run pprog input with
 | Success(result, _, _) -> result
 | Failure(msg, _, _) -> failwith msg

let program = parse myFile

The program variable is of the type AST.program (no need to show the implementation), thanks to the matching pattern of the parse function. If I do only this:

let program = run pprog myFile

program is of the type ParserResult<AST.Program, unit>, which is therefore unanalyzable.

I was wondering if there was a way not to crash the program with the exceptions launched?

asked Nov 10 at 12:16

Foxy

189110

I would like to be able to parse a file without the program launching an exception and stop the program at the first error. I use this:

let parse input = match run pprog input with
 | Success(result, _, _) -> result
 | Failure(msg, _, _) -> failwith msg

let program = parse myFile

The program variable is of the type AST.program (no need to show the implementation), thanks to the matching pattern of the parse function. If I do only this:

let program = run pprog myFile

program is of the type ParserResult<AST.Program, unit>, which is therefore unanalyzable.

I was wondering if there was a way not to crash the program with the exceptions launched?

.net parsing exception f# fparsec

asked Nov 10 at 12:16

Foxy

189110

asked Nov 10 at 12:16

Foxy

189110

asked Nov 10 at 12:16

Foxy

189110

asked Nov 10 at 12:16

Foxy

189110

asked Nov 10 at 12:16

Foxy

189110

How to not crash with an exception is easy: just use a try ... with block, and handle the exception in the with part. BUT... there's something you haven't mentioned in your question, which is: what do you want your program to do if FParsec parsing fails? How do you want your program to handle invalid input? Once you've decided the answer to that question, then all you need to do is to put that logic in the Failure branch of your parse function, instead of throwing an exception with failwith in that branch. So ask yourself this: what do you want to do with invalid input?
– rmunn
Nov 10 at 22:41

@rmunn – FParsec, during its parsing, already displays the errors. failwith launches an exception (which crashes the program on the way), but if I could avoid it it would be fine with me. Only, the parse function must be of the following type: string -> AST.Program. So I must necessarily return a data of the type AST.Program, or run an exception. But if there is a way to have a function of this type that does not launch an exception, I would be happy to know.
– Foxy
Nov 10 at 23:16

Does your AST.Program type have some kind of "empty" value? E.g., if it's a list of expressions, the "empty" value would be an empty list. If so, then your parse function could return the parsed program on success, and an empty program on failure.
– rmunn
2 days ago

@rmunn – I had thought about it at the beginning, and indeed there are no more exceptions, only it doesn't display errors, and stops the first time. What I'm actually looking for is a way to get an AST.Program data, and for all errors to be displayed without any exceptions. I also think that my way of doing things in the initial post is not correct in terms of what I would like to do in relation to the match. I looked at the documentation, but it doesn't deal with the subject.
– Foxy
yesterday

add a comment |

How to not crash with an exception is easy: just use a try ... with block, and handle the exception in the with part. BUT... there's something you haven't mentioned in your question, which is: what do you want your program to do if FParsec parsing fails? How do you want your program to handle invalid input? Once you've decided the answer to that question, then all you need to do is to put that logic in the Failure branch of your parse function, instead of throwing an exception with failwith in that branch. So ask yourself this: what do you want to do with invalid input?
– rmunn
Nov 10 at 22:41

@rmunn – FParsec, during its parsing, already displays the errors. failwith launches an exception (which crashes the program on the way), but if I could avoid it it would be fine with me. Only, the parse function must be of the following type: string -> AST.Program. So I must necessarily return a data of the type AST.Program, or run an exception. But if there is a way to have a function of this type that does not launch an exception, I would be happy to know.
– Foxy
Nov 10 at 23:16

Does your AST.Program type have some kind of "empty" value? E.g., if it's a list of expressions, the "empty" value would be an empty list. If so, then your parse function could return the parsed program on success, and an empty program on failure.
– rmunn
2 days ago

@rmunn – I had thought about it at the beginning, and indeed there are no more exceptions, only it doesn't display errors, and stops the first time. What I'm actually looking for is a way to get an AST.Program data, and for all errors to be displayed without any exceptions. I also think that my way of doing things in the initial post is not correct in terms of what I would like to do in relation to the match. I looked at the documentation, but it doesn't deal with the subject.
– Foxy
yesterday

How to not crash with an exception is easy: just use a try ... with block, and handle the exception in the with part. BUT... there's something you haven't mentioned in your question, which is: what do you want your program to do if FParsec parsing fails? How do you want your program to handle invalid input? Once you've decided the answer to that question, then all you need to do is to put that logic in the Failure branch of your parse function, instead of throwing an exception with failwith in that branch. So ask yourself this: what do you want to do with invalid input?
– rmunn
Nov 10 at 22:41

@rmunn – FParsec, during its parsing, already displays the errors. failwith launches an exception (which crashes the program on the way), but if I could avoid it it would be fine with me. Only, the parse function must be of the following type: string -> AST.Program. So I must necessarily return a data of the type AST.Program, or run an exception. But if there is a way to have a function of this type that does not launch an exception, I would be happy to know.
– Foxy
Nov 10 at 23:16

Does your AST.Program type have some kind of "empty" value? E.g., if it's a list of expressions, the "empty" value would be an empty list. If so, then your parse function could return the parsed program on success, and an empty program on failure.
– rmunn
2 days ago

@rmunn – I had thought about it at the beginning, and indeed there are no more exceptions, only it doesn't display errors, and stops the first time. What I'm actually looking for is a way to get an AST.Program data, and for all errors to be displayed without any exceptions. I also think that my way of doing things in the initial post is not correct in terms of what I would like to do in relation to the match. I looked at the documentation, but it doesn't deal with the subject.
– Foxy
yesterday

add a comment |

active

oldest

votes

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',
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
);

);

draft saved

draft discarded

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53238860%2fhandling-exceptions-with-fparsec%23new-answer', 'question_page');

);

Post as a guest

Name

active

oldest

votes

draft saved

draft discarded

draft saved

draft discarded

Post as a guest

Name

This page is only for reference, If you need detailed information, please check here

搜尋此網誌

Myujth