The naked truth about writing a programming language (2014)
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The naked truth about writing a programming language (2014)
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Re: The naked truth about writing a programming language (2014)
#2I want to implement a toy programming language, but I have questions regarding the following in that article:
> Context free grammars. What this really means is the code should be parseable without having to look things up in a symbol table. C++ is famously not a context free grammar. A context free grammar, besides making things a lot simpler, means that IDEs can do syntax highlighting without integrating in most of a compiler front end, i.e. third party tools become much more likely to exist.
Many complex languages, like c++, rust are not context free. We therefore need semantic analysis.
What programming language features will be compromised if I stick to context free?
Will the end result be as expressive as c++/rust?
Any programming language that is massively adopted is context free?
BTW, the toy language I want to build will be something similar to javascript.
Re: The naked truth about writing a programming language (2014)
#3I want to implement a toy programming language, but I have questions regarding the following in that article: > Context free grammars. What this really means is the code should be parseable without having to look things up in a symbol table. C++ is famously not a context free grammar. A context free grammar, besides making things a lot simpler, means that IDEs can do syntax highlighting without integrating in most of…
Rust is almost context free; there’s one relatively rarely used bit that requires context. And usually it’s only one or two bytes of it.
Re: The naked truth about writing a programming language (2014)
#4I want to implement a toy programming language, but I have questions regarding the following in that article: > Context free grammars. What this really means is the code should be parseable without having to look things up in a symbol table. C++ is famously not a context free grammar. A context free grammar, besides making things a lot simpler, means that IDEs can do syntax highlighting without integrating in most of…
Rust is almost context free; there’s one relatively rarely used bit that requires context. And usually it’s only one or two bytes of it.
You're referring to raw string literals, right?
Re: The naked truth about writing a programming language (2014)
#5,,grammar should be redundant. You’ve all heard people say that statement terminating ; are not necessary because the compiler can figure it out. ''
I'll stay with my non-redundant Julia language, thank you very much. It gave me a lot of joy to programming, and I don't remember having big problems with error messages. Even if I have, syntactic errors are trivial to find.
The hard parts of efficient programming are memory management (garbage collection), controlling vectorizing instructions, balance between ease of GPU programming and efficiency, parallelization, not semicolons at the end of a line.
All programming languages have to decide on how low level control they give to the computer resources, and how they abstract them, to make high level programming possible without sacrificing too much efficiency.
Re: The naked truth about writing a programming language (2014)
#6I want to implement a toy programming language, but I have questions regarding the following in that article: > Context free grammars. What this really means is the code should be parseable without having to look things up in a symbol table. C++ is famously not a context free grammar. A context free grammar, besides making things a lot simpler, means that IDEs can do syntax highlighting without integrating in most of…
https://stackoverflow.com/questions/898489/what-programming-...
Most languages have context-free syntax, which is what the article refers too. There really is no reason to sacrifice that. Even modern PHP recognises the value of having a parse tree independent of an entire compiler.
Context-free semantics is an entirely different matter, and I'm not even sure what it'd mean...
Re: The naked truth about writing a programming language (2014)
#7I want to implement a toy programming language, but I have questions regarding the following in that article: > Context free grammars. What this really means is the code should be parseable without having to look things up in a symbol table. C++ is famously not a context free grammar. A context free grammar, besides making things a lot simpler, means that IDEs can do syntax highlighting without integrating in most of…
Rust is almost context free; there’s one relatively rarely used bit that requires context. And usually it’s only one or two bytes of it.
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Re: The naked truth about writing a programming language (2014)
#8After learning s-expression based syntax, I am just baffled why we even bother with anything else.
When you play around with different Lisps, the syntax is always the same, the language differences becomes the semantics only.
Other languages put too much emphasis on the syntax in my opinion. And while I understand the "popularity" appeal. I've almost never seen someone learning the s-expression syntax and afterwards not liking it.
Basically I think it be worth it to push people to learn the s-expression syntax just so we can stop wasting our time with syntax afterwards.
Also if I recall, without user macros, I think s-expression syntax is context free no?
Re: The naked truth about writing a programming language (2014)
#9I want to implement a toy programming language, but I have questions regarding the following in that article: > Context free grammars. What this really means is the code should be parseable without having to look things up in a symbol table. C++ is famously not a context free grammar. A context free grammar, besides making things a lot simpler, means that IDEs can do syntax highlighting without integrating in most of…
https://stackoverflow.com/questions/898489/what-programming-... Most languages have context-free syntax, which is what the article refers too. There really is no reason to sacrifice that. Even modern PHP recognises the value of having a parse tree independent of an entire compiler. Context-free semantics is an entirely different matter, and I'm not even sure what it'd mean...
The two top answers are in conflict. The second answer with 43 points is closer to right:
There are hardly any real-world programming languages that are context-free in any meaning of the word.
The first answer with 41 points is totally wrong: The set of programs that are syntactically correct is context-free for almost all languages
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A better source is this whole series by Trevor Jim, which has nice ways of relating theory to practice. He lists a bunch of reasons why you could consider nearly all programming languages not context-free.
http://trevorjim.com/parsing-not-solved/ -- hundreds of parser generators support context-free grammars, but there are almost no context-free languages in practice.
http://trevorjim.com/python-is-not-context-free/ -- A main point here is that you have to consider the lexer and parser separately. Grammars don't address this distinction, which arises in essentially all programming languages. Also there is some lexical feedback, similar in spirit to C's lexer hack.
http://trevorjim.com/haskell-is-not-context-free/
http://trevorjim.com/how-to-prove-that-a-programming-languag...
http://trevorjim.com/c-and-cplusplus-are-not-context-free/ -- the way LALR(1) conflicts are resolved in practice can make a language not context-free
(copying from a recent comment)
Re: The naked truth about writing a programming language (2014)
#10After learning s-expression based syntax, I am just baffled why we even bother with anything else. When you play around with different Lisps, the syntax is always the same, the language differences becomes the semantics only. Other languages put too much emphasis on the syntax in my opinion. And while I understand the "popularity" appeal. I've almost never seen someone learning the s-expression syntax and afterwards…
It's simple, but it's fundamentally reductionist. You can ease the cognitive load by making certain programming structures first-class citizens in the language.