Parse chars in escape sequence form

Question

I'm implementing a compiler, and I need to convert from an escape character literal written in source code file to an actual value.

For example I might have a line of source code char = '\\'. I then parse that and get given the string "'\\'", which I need to turn into the actual char '\\'.

char.Parse and char.TryParse both fail when parsing a char in escape sequence form. For example:

char.Parse(@"\\");

Will throw "String must be exactly one character long."

Is there any way to parse everything on this list as a char (ignoring those that are to big to fit in a UTF16 char).

How are you getting this "*escape sequence form*" ? who is supplying it, or are you getting confused at what you are seeing in the visual studio editor ? — TheGeneral, Nov 16 '19 at 20:13
The string shown in the sample is 2 characters long (2 back slashes) - could you please clarify what do you expect to happen? — Alexei Levenkov, Nov 16 '19 at 20:13
@AlexeiLevenkov I'm implementing a compiler, and I need to convert from an escape character literal in the form of eg "//" to an actual value. — Yair Halberstadt, Nov 16 '19 at 20:21
It sounds like https://stackoverflow.com/questions/3298075/can-i-expand-a-string-that-contains-c-sharp-literal-expressions-at-runtime is your actual question... but it is *very* hard to get to from sample in your post... — Alexei Levenkov, Nov 16 '19 at 20:23
Sorry @AlexeiLevenkov. I have my head in the context, so it feels very obvious to me, but I can see how it could seem very confusing to someone outside the context. Thanks for the link. — Yair Halberstadt, Nov 16 '19 at 20:26

score 5 · Answer 1 · answered Nov 16 '19 at 20:14

5

the @ makes it a verbatim string literal. drop that and \ will be treated as the escape char for the next \.

@"\\".Length // 2
"\\".Length // 1

answered Nov 16 '19 at 20:14

Daniel A. White

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This is coming in from a string - that was just by way of example – Yair Halberstadt Nov 16 '19 at 20:19
in that case @YairHalberstadt please provide a [mcve] in your question. – Daniel A. White Nov 16 '19 at 20:20
That is a minimal reproducible example. It's just that since I'm reading a string from a file, I can't drop the @. – Yair Halberstadt Nov 16 '19 at 20:22
@YairHalberstadt that makes no sense. verbatim string literals are a compile time thing. – Daniel A. White Nov 16 '19 at 20:23
@DanielA.White I think the actual question is https://stackoverflow.com/questions/3298075/can-i-expand-a-string-that-contains-c-sharp-literal-expressions-at-runtime – Alexei Levenkov Nov 16 '19 at 20:24
I have a source code file containing something like '\\'. The parser gives me "'\\'". I need to say "thats equavalent to the char '\\'. – Yair Halberstadt Nov 16 '19 at 20:24

Parse chars in escape sequence form

1 Answers1