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Writing Your Own Programming Language

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Re: Writing Your Own Programming Language

#11

Post by inimino »

keithb- wrote: post #9
drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

I think you're asking the right questions. I would assume that your class targeted Lisp because SICP uses it. While that is a great resource, it is light on details when it comes to the end game: runtime. If you are developing a language today and you aren't considering runtime, then you are just writing macros. Lexing, and parsing are not trivial tasks, but powerful tooling already exists for these. Compiling means…

I'm not sure what you mean by "runtime" here and I'm having a little trouble seeing what you're getting at.

Re: Writing Your Own Programming Language

#12

Post by jedimastert »

drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

I think it's because the text representation is super close to the AST

Re: Writing Your Own Programming Language

#13

Post by kazinator »

drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

If the language supports assignment, which allows variables and parts of data structures to be treated as mutable memory locations, then it isn't functional.

Using Lisp syntax lets the class have more time for semantics.

Re: Writing Your Own Programming Language

#14

Post by throwaway2016a »

drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

Because languages like this map so closely to the AST (as someone else pointed out) you don't need to deal with complexities such as look aheads, regular expressions, and formal syntax definitions (BNFs). I suppose this makes it a good getting started point.

Most more complex languages you'd use something like lex and yacc which would add quite a bit more overhead to the tutorial.

The danger of these tutorials is the whole "grow your own parser" method doesn't scale to more complex languages (you need better tooling for that and/or a lot firmer grasp of the concepts) and I would be concerned that people would try to extend this tutorial and go down a rabbit hole.

Edit: I know this from experience because when I was in high school I wrote a compiler this way (let's call it the naive way). And then in college I learned how to do it with BNF and code generators and the difference in maintainability and code complexity between the two is ridiculous. I would never do it the old way again, even for a toy language.

Re: Writing Your Own Programming Language

#16

Post by ufo »

drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

It depends on hoe you are writing your compiler. If you are coding in a high level language, then writing an AST interpreter for a functional language is super simple. You just need to mix first-class functions and an unsurprising expression evaluator and you end up with something really expressive.

If you are targeting a lower level language like assembly language then I think an imperative language is easier to do though. You need to worry a lot about memory layouts, register allocation and calling conventions and in this paradigm a simple imperative language will be an easier fit.

Re: Writing Your Own Programming Language

#17

Post by tscs37 »

drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

I can probably answer the LISP question; the Core LISP Languages is incredibly simple. It has only 8 or so keywords you really need and 5 syntax forms (probably wrong, I don'T have the exact numbers in my head)

It comes with very few special forms and makes no difference between a variable, function or macro. Everything is same-y.

Re: Writing Your Own Programming Language

#18

Post by greenshackle2 »

throwaway2016a wrote: post #14
drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

Because languages like this map so closely to the AST (as someone else pointed out) you don't need to deal with complexities such as look aheads, regular expressions, and formal syntax definitions (BNFs). I suppose this makes it a good getting started point. Most more complex languages you'd use something like lex and yacc which would add quite a bit more overhead to the tutorial. The danger of these tutorials is the…

I'm writing an assembler for a virtual 16 bit CPU I built, and I hesitated on using BNF. It seemed overkill so I ended up hand-rolling a parser; for an assembler it's straightforward enough, but I can easily see how it could get ridiculous to implement a compiler this way.

Re: Writing Your Own Programming Language

#20

Post by vidarh »

throwaway2016a wrote: post #14
drusepth wrote: post #3

Honest question: why do tutorials in this topic seem to always use functional languages/syntax as examples? Our compilers class at MST had us re-implement a lisp compiler, but didn't touch on why we used lisp specifically (other than the professor liking it; we were a largely C++ school). Do they think functional languages are simpler / less complex / easier to understand? Is there something inherently easier to impl…

Because languages like this map so closely to the AST (as someone else pointed out) you don't need to deal with complexities such as look aheads, regular expressions, and formal syntax definitions (BNFs). I suppose this makes it a good getting started point. Most more complex languages you'd use something like lex and yacc which would add quite a bit more overhead to the tutorial. The danger of these tutorials is the…

> Most more complex languages you'd use something like lex and yacc which would add quite a bit more overhead to the tutorial.

Very few production compilers use lex/yacc type parsers, because error handling and recovery is painful. Most end up with hand-written recursive-descent parsers.

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