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C4 – C in 4 functions

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Re: C4 – C in 4 functions

#21

Post by marcofiset »

mturmon wrote: post #11
marcofiset wrote: post #4

I honestly think this is ridiculous. Sure, this is an incredible feat, and congrats. But serioulsy, I would be ashamed to publish such unreadable code under my name. What about naming your variables with descriptive names? What about extracting complex conditions into well named function to understand what is going on (thus defeating the purpose of the "4 functions") ? This list could go on forever... Writing softwar…

> This list could go on forever... Yes it could. While you are adding to your list of coding rules, the OP will have written another fun, tiny compiler. Who is having more fun?

Those are not rules, they are mostly common sense to help the next programmer who has to maintain your code.

Re: C4 – C in 4 functions

#22

Post by marcofiset »

cbhl wrote: post #15
marcofiset wrote: post #4

I honestly think this is ridiculous. Sure, this is an incredible feat, and congrats. But serioulsy, I would be ashamed to publish such unreadable code under my name. What about naming your variables with descriptive names? What about extracting complex conditions into well named function to understand what is going on (thus defeating the purpose of the "4 functions") ? This list could go on forever... Writing softwar…

I actually found the code surprisingly easy to read; "tk" stands for "token", "ty" for "type", and so forth. It's worth noting that compilers don't pop out of thin air -- you have to start with something simple in order to compile a more complicated compiler. Bootstrapping your own self-hosting compiler is a useful academic exercise, and you should try it sometime if you haven't already: http://en.wikipedia.org/wiki/…

Well, if this particular compiler is defined in 4 functions, why couldn't it be made out of more functions, enhancing the readability and maintainability of the code?

Re: C4 – C in 4 functions

#23

Post by abecedarius »

On a first skim, this looks really nice; complaints that it's unreadable are unfounded. The background that makes it readable are Wirth's Compiler Construction http://www.ethoberon.ethz.ch/WirthPubl/CBEAll.pdf plus precedence climbing http://en.wikipedia.org/wiki/Operator-precedence_parser#Prec...

Re: C4 – C in 4 functions

#24

Post by fla »

marcofiset wrote: post #4

I honestly think this is ridiculous. Sure, this is an incredible feat, and congrats. But serioulsy, I would be ashamed to publish such unreadable code under my name. What about naming your variables with descriptive names? What about extracting complex conditions into well named function to understand what is going on (thus defeating the purpose of the "4 functions") ? This list could go on forever... Writing softwar…

The goal here is to write a compiler that can compile itself.

Re: C4 – C in 4 functions

#25

Post by marktangotango »

0x0 wrote: post #18

Would you call this a compiler, an interpreter, a virtual machine, a scripting engine, or a combination of those?

It compiles a c subset to byte code, then executes in a virtual machine. I think generally an intepreter can refer to either a byte code interpreter (ie virtual machine) or an AST walking interpreter. I didn't see a way to embed c4 into a host language, so maybe not a scripting language?

IMO the real value of exhibits like this are boiling the problem (lexing, parsing, compiler, interpreting) down to their most basic parts. One could easily imagine this same language being implemented over 10's or 100's of class files in a more verbose language.

Re: C4 – C in 4 functions

#26

Post by afandian »

marcofiset wrote: post #21
mturmon wrote: post #11

Earlier quoted context omitted.

> This list could go on forever... Yes it could. While you are adding to your list of coding rules, the OP will have written another fun, tiny compiler. Who is having more fun?

Those are not rules, they are mostly common sense to help the next programmer who has to maintain your code.

And most common sense of all is that you choose your rules for the audience. This is obviously not production code.

In any case if someone were competent enough to work on it then the style is actually quite readable. It's even full of comments.

Re: C4 – C in 4 functions

#27

Post by afandian »

marcofiset wrote: post #22
cbhl wrote: post #15

Earlier quoted context omitted.

I actually found the code surprisingly easy to read; "tk" stands for "token", "ty" for "type", and so forth. It's worth noting that compilers don't pop out of thin air -- you have to start with something simple in order to compile a more complicated compiler. Bootstrapping your own self-hosting compiler is a useful academic exercise, and you should try it sometime if you haven't already: http://en.wikipedia.org/wiki/…

Well, if this particular compiler is defined in 4 functions, why couldn't it be made out of more functions, enhancing the readability and maintainability of the code?

Who says it's designed to be maintainable? Not everyone writes code for the reason that everyone else does.

Re: C4 – C in 4 functions

#29

Post by cremno »

methyl wrote: post #9

Unfortunately, I cannot compile it on my OSX 10.10... here's what I get: http://pastebin.com/cVvaYFEH EDIT: just make next() function void and it works. EDIT2: still no fortune :( $ ./c4 hello.c [1] 33920 segmentation fault ./c4 hello.c

I think it doesn't work on x86-64, since the code assumes

    sizeof(int) == sizeof(void*)

Re: C4 – C in 4 functions

#30

Post by jparishy »

cremno wrote: post #29
methyl wrote: post #9

Unfortunately, I cannot compile it on my OSX 10.10... here's what I get: http://pastebin.com/cVvaYFEH EDIT: just make next() function void and it works. EDIT2: still no fortune :( $ ./c4 hello.c [1] 33920 segmentation fault ./c4 hello.c

I think it doesn't work on x86-64, since the code assumes sizeof(int) == sizeof(void*)

Yep, you can compile it on 64 bit OS X with clang's -m32 option and it should work:

    ➜  c4 git:(master) ✗ clang -m32 c4.c
    ...
    ➜  c4 git:(master) ✗ ./a.out hello.c 
    hello, world
    exit(0) cycle = 9
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