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Questions tagged [language-implementation]

Having to do with issues arising when implementing a programming language.

141 questions
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What Lisp is better at parsing?

I'd like to implement a Lisp interpreter in a Lisp dialect mainly as a learning exercise. The one thing I'm thrown off by is just how many choices there are in this area. Primarily, I'm a bit more interested in learning about some of the Lisps…
Jason Baker
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Internal implementation of java.util.HashMap and HashSet

I have been trying to understand the internal implementation of java.util.HashMap and java.util.HashSet. Following are the doubts popping in my mind for a while: Whats is the importance of the @Override public int hashcode() in a HashMap/HashSet?…
peakit
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How are arrays implemented in Perl?

The Perl array is an abstract data type. What's the internal mechanism for the Perl array? Is it implemented with dynamic array or linked list? Since the array elements have random access, I would assume a dynamic array of pointers, or references…
Jason X
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Why does binding affect the type of my map?

I was playing around in the REPL and I got some weird behavior: Clojure 1.4.0 user=> (type {:a 1}) clojure.lang.PersistentArrayMap user=> (def x {:a 1}) #'user/x user=> (type x) clojure.lang.PersistentHashMap I thought that all small literal maps…
DaoWen
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Does the range for integer values of a char depend on implementation?

I'm reading The C++ Programming Language and in it Stroustrup states that the int value of a char can range from 0 to 255 or -127 to 127, depending on implementation. Is this correct? It seems like it should be from -128 to 127. If not, why are…
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Garbage collection implementation in compiled languages

When implementing precise garbage collection, there is always the issue of figuring out which words on the stack are pointers and which are other kinds of data such as integers or floating point numbers. Interpreted languages typically solve this…
rwallace
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Understanding the implementation of memcpy()

I was looking the implementation of memcpy.c, I found a different memcpy code. I couldnt understand why do they do (((ADDRESS) s) | ((ADDRESS) d) | c) & (sizeof(UINT) - 1) #if !defined(__MACHDEP_MEMFUNC) #ifdef _MSC_VER #pragma…
Angus
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Why does `vector` implementation have multiple cases?

Here's clojure's definition of vector: (defn vector "Creates a new vector containing the args." {:added "1.0" :static true} ([] []) ([a] [a]) ([a b] [a b]) ([a b c] [a b c]) ([a b c d] [a b c d]) ([a b c d & args] (.…
Matt Fenwick
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Is there a Scheme implementation that parallelizes?

Is there a R5RS-or-higher Scheme implementation that does parallelization? For example, if I say to do: (map (lambda (x) (pure-functional-stuff x)) '(1 3 5 7 11 13)) it will process 1, 3, 5, and 7 simultaneously if the machine can do…
JasonFruit
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A smart garbage collector for sharing subranges of arrays?

In this popular question about why substring takes O(n) in C#, one of the main answers provided argued that if a large array were allocated and substrings computed by having the new strings just reference a small slice of the array, the garbage…
templatetypedef
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2 answers

Compiling functional languages to C

Suppose you're compiling a functional language to portable C, and suppose also that for various reasons you want precise rather than conservative garbage collection. There is no portable way (perhaps no way at all in the general case) for the…
rwallace
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4 answers

Haskell: Why ++ is not allowed in pattern matching?

Suppose we want to write our own sum function in Haskell: sum' :: (Num a) => [a] -> a sum' [] = 0 sum' (x:xs) = x + sum' xs Why can't we do something like: sum' :: (Num a) => [a] -> a sum' [] = 0 sum' (xs++[x]) = x + sum' xs In other words why…
Abhisek
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How does a macro-enabled language keep track of the source code for debugging?

This is a more theoretical question about macros (I think). I know macros take source code and produce object code without evaluating it, enabling programmers to create more versatile syntactic structures. If I had to classify these two macro…
Sean Woods
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How to implement a practical fiber scheduler?

I know the very basics about using coroutines as a base and implementing a toy scheduler. But I assume it's oversimplified view about asynchronous schedulers in whole. There are whole set of holes missing in my thoughts. How to keep the cpu from…
Cheery
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Source code of implementation JavaScript internal methods

Is there a way to see the code behind a JavaScript's method? Not a javascript method from the website's .html or .js files, but JavaScript's internal methods. For example: How can I see how JavaScript calculates the offsetTop of an element?
Fistright
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