I use Python, but I don't know how it works in Kotlin. This is an example
example => exec("""print("hello")""") output => hello
exec("""print("hello")""") output => hello
Kotlin supports JSR-223. You can use the jvm scripting engine to eval kts files.
val engine = ScriptEngineManager().getEngineByExtension("kts")
engine.eval("""print("hello")""")
You need JSR-223 library dependency. Refer to example
implementation("org.jetbrains.kotlin:kotlin-scripting-jsr223:$kotlinVersion")
Short answer: this isn't practical in Kotlin.
Technically, there may be ways, but they're likely to be far more trouble than they're worth; you're far better looking for a different approach to your problem.
Unlike a dynamic (‘scripting’) language like Python, Kotlin is statically-compiled. In the case of Kotlin/JVM, you run the Kotlin compiler to generate .class files with Java bytecode, which is then run by a JVM.
So if you really need to convert a string into code and run it, you'd have to find a way to ensure that a Kotlin compiler is available on the platform where your code is running (which it often won't be; compiled bytecode can run on any platform with a JVM, and most of those won't have Kotlin installed too). You'd then have to find a way to run the compiler; this will probably mean writing your source code out to a file, starting up the compiler program as a separate process (as I don't think there's an API for calling it directly), and checking the results. Then you'd have find the resulting bytecode and load into the JVM, which will probably mean setting up a separate classloader instance.
All of which is likely to be slow, fragile, and very awkward.
(See these previous questions which cover some of the same ground.)
(The details will be different for Kotlin/JS and Kotlin/Native, but I think the principles are roughly the same.)
In general, each computer language has its own approach, its own mind-set and ways of doing things, and it's best to try to understand that and accept that patterns and techniques from one language don't always translate well into another. (In the Olden Days™, it used to be said that a determined programmer could write FORTRAN programs in any language — but only in satire.)
Perhaps if you could explain why you want to do this, and what sort of problem you're trying to solve (probably as a separate question), we might be able to suggest more natural solutions in Kotlin.
I am trying to create a synchronized usrp source block in gnu radio consisting of multiple B210 USRP devices. Lang: C++.
From what I have found I need to:
Instantiate multiple multi_usrp_sptr as each B210 requires one and multiple B210 devices cannot be addressed by using single sptr
Use external frequency and PPS sources - an option that can be selected from block or set programmatically
Synchronize re/tuning to achieve repeatable phase offset between nodes - this can be achieved using timed commands API https://kb.ettus.com/Synchronizing_USRP_Events_Using_Timed_Commands_in_UHD
Synchronize sample streams using time_spec property issue_stream cmd
The problem is how should I insert these timed commands and set time_spec of stream in GNU radio block or gr-uhd libs?
I looked into the gr-uhd folder where the sink/source code resided and found functions that could be altered.
Unfortunately I don't know how to copy or export this library to do these modifications and later compile to insert my custom blocks to GNU Radio, because gr-uhd seems to be built in and compiled at GR installation.
I attempted coping and then making the lib but that's not the way - it didn't succeed. Should I add my own source block via gr_modtool and insert only the commands I need?
Compatibility with uhd and its functions apart from just adding a few lines would be advantageous not to write the source from scratch.
Please advise
Edit
Experimental flowchart, based on Marcus Müller suggestion:
Experimental usrp synchronization flow
The problem is how should I insert these timed commands and set time_spec of stream in GNU radio block or gr-uhd libs?
For a USRP sink: add tags containing dictionaries with the correct command times to the streams. The GNU Radio API docs have information on how these dictionaries need to look like. The time field is what you need to set with an appropriate value.
For a USRP source: Use the set_start_time on the uhd_usrp_source block; use the same dictionaries described above to issue commands like tuning, gain setting at a coordinated time.
I was trying to find a proper way of synchronizing the USRPs via tags.
There are a few issues I came across in this approach:
Timed commands require the knowledge of the current moment in time, which is done via usrp.get_time_now(), even though I would request the USRP to give the time through tags I would have to somehow extract it from the output. (make some kind of loop and proper triggering) (source: https://kb.ettus.com/Synchronizing_USRP_Events_Using_Timed_Commands_in_UHD) or maybe plan everything not in a relative way - using absolute values instead of offsets. I have seen an approach to regularly reset the sense of time each PPS (set it to 0.0) and maybe then setting time of commands within range of 0.0-1.0 would be acceptable. Then the loop for reading and inserting time into commands would also be redundant.
I didn't found a way to create dicts in GR via blocks to make the solution scalable (without writing a few lines of code in textbox) or writing OOT block
In the end there is so little information to tell what kind of solution is most appropriate (PDU, events, are tags still relevant in GR
?), and the docs are so very scarce, that after some mailing I decided to add a simple class that inherits from the main top_bock.py and after instantiation of top_block it calls a few functions to synchronize the devices. This kind of solution is not the most flexible one, and the parent class top_block.py has to be called through the inheriting one, but it enables an easy programming interface.
Soon I will add an example of the code used in inheriting class just in case.
If there is any more neat, dynamic or scalable solution please let me know or point me to sources.
I'm currently trying to do some real-time signal-processing and I would like to use "gnuradio". I will be processing multiple channels of EEG which come in trough a custom interface (namely "Lab Streaming Layer"; LSL) in python.
Now my question is if there is an existing block already where you can kind of "push" samples into the signal-processing-graph during run-time? The only blocks I've found so far offer support for audio hardware, TCP-streams and files.
You will have to write your own block; that can be done in Python or C++, whatever is better for your case.
The GNU Radio Guided Tutorials (you should really read them in order from 1 to 5, at least) do explain how to do that.
Because we all know that people are lazy at reading, here's a rough preview of what you'll learn:
make a new Out-of-tree module: gr_modtool newmod sensorinterface, change into the newly generated directory: cd gr-sensorinterface
add a new source block: gr_modtool add eeg_sensor_source; the block type you'll want is "source"; you will be asked to fill in some block details.
edit the generated source file (in lib/ or python/, depending on which language you chose:
add a proper io signature: your output will probably have the size of float
edit the central work function; add code to get new samples, and copy those to the output_items buffer.
The guided tutorials are really nice!
The most flexible method is to write your own GNU Radio block, but there are several options for getting data into a flow graph without using any custom blocks. (Naming from the Python perspective.)
gnuradio.blocks.message_source, which takes data from a gnuradio.gr.msg_queue.
You can use a gnuradio.blocks.file_descriptor_source where the file descriptor is one end of a pipe.
I don't know, if this question is valid since i'm not very familiar with source code parsing. My goal is to write a source code completion function for one existing programming language (Language "X") for learning purposes.
Is Antlr(v4) suitable for such a task or should the necessary AST/Parse Tree creation and parsing be done by hand, assuming no existing solutions exists?
I haven't found much information about that specific topic, except a list of compiler books, except a compiler is not what i'm after for.
The code completion in GoWorks is completely implemented using ANTLR 4. The following video shows the level of completion of this code completion engine. The code completion example runs from 5 minutes through the end of the video.
Intro to Tunnel Vision Labs' GoWorks IDE (Preview Release)
I have been working on code completion algorithms for many years, and strongly believe that there is no better solution (automated or manual) for producing a code completion solution for a new language that meets the requirements for what I would call highly-responsive code completion. If you are not interested in that level of performance or accuracy, other solutions may be easier for you to get involved with (I don't work with those personally, because I am too easily disappointed in the results).
Xtext uses ANTLR3 and has good autocomplete facilities. The problem is, it generates a seperate parser (again using antlr3) for autocomplete processing which is derived from AbstractInternalContentAssistParser. This multi-thousand line code part shows that the error recovery of ANTLR3 alone found to be insufficient by the xtext team.
Meanwhile ANTLR4 has a function parser.getExpectedTokensWithinCurrentRule() which lists possible token types for given position. It works when used in a ParseTreeListener. Remaining is semantics, scoping etc which is out of ANTLRs scope.
I am dabbling in PHP and getting my feet wet browsing SO, and feel compelled to ask a question that I've been wondering about for years:
When you write an entirely new programming language, what do you write it in?
It's to me a perplexing chicken & egg thing to me. What do you do? Say to yourself Today I'm going to invent a new language! and then fire up. Notepad? Are all compilers built on previously existing languages, such that were one to bother one could chart all programming languages ever devised onto one monstrous branching tree that eventually grounded out at... I don't know, something old?
It's not a stupid question. It's an excellent question.
As already answered the short answer is, "Another language."
Well that leads to some interesting questions? What if its the very first language written for
your particular piece of hardware? A very real problem for people who work on embedded devices. As already answered "a language on another computer". In fact some embedded devices will never get a compiler, their programs will always be compiled on a different computer.
But you can push it back even further. What about the first programs ever written?
Well the first compilers for "high level languages" would have been written in whats called "assembly language". Assembly language is a language where each instruction in the language corresponds to a single instruction to the CPU. Its very low level language and extremely verbose and very labor intensive to write in.
But even writing assembly language requires a program called an assembler to convert the assembly language into "machine language". We go back further. The very first assemblers were written in "machine code". A program consisting entirely of binary numbers that are a direct one-to-one correspondence with the raw language of the computer itself.
But it still doesn't end. Even a file with just raw numbers in it still needs translation. You still need to get those raw numbers in a file into the computer.
Well believe it or not the early computers had a row of switches on the front of them. You flipped the switches till they represented a binary number, then you flicked another switch and that loaded that single number into the computers memory. Then you kept going flicking switched until you had loaded a minimal computer program that could read programs from disk files or punch cards. You flicked another switch and it started the program running. When I went to university in the 80's I saw computers that had that capacity but never was given the job of loading in a program with the switches.
And even earlier than that computer programs had to be hard wired with plug boards!
The most common answer is C. Most languages are implemented in C or in a hybrid of C with callbacks and a "lexer" like Flex and parser generator like YACC. These are languages which are used for one purpose - to describe syntax of another language. Sometimes, when it comes to compiled languages, they are first implemented in C. Then the first version of the language is used to create a new version, and so on. (Like Haskell.)
A lot of languages are bootstrapped- that is written in themselves. As to why you would want to do this, it is often a good idea to eat your own dogfood.
The wikipedia article I refer to discusses the chicken and egg issue. I think you will find it quite interesting.
Pretty much any language, though using one suited to working with graphs and other complex data structures will make many things easier. Production compilers are often written in C or C++ for performance reasons, but languages such as OCaml, SML, Prolog, and Lisp are arguably better for prototyping the language.
There are also several "little languages" used in language design. Lex and yacc are used for specifying syntax and grammars, for example, and they compile to C. (There are ports for other languages, such as ocamllex / ocamlyacc, and many other similar tools.)
As a special case, new Lisp dialects are often built on existing Lisp implementations, since they can piggyback on most of the same infrastructure. Writing a Scheme interpreter can be done in Scheme in under a page of code, at which point one can easily add new features.
Fundamentally, compilers are just programs that read in something and translate it to something else - converting LaTeX source to DVI, converting C code to assembly and then to machine language, converting a grammar specification to C code for a parser, etc. Its designer specifies the structure of the source format (parsing), what those structures mean, how to simplify the data (optimizing), and the kind of output to generate. Interpreters read the source and execute it directly. (Interpreters are typically simpler to write, but much slower.)
"Writing a new programming language" technically doesn't involve any code. It's just coming up with a specification for what your language looks like and how it works. Once you have an idea of what your language is like, you can write translators and interpreters to actually make your language "work".
A translator inputs a program in one language and outputs an equivalent program in another language. An interpreter inputs a program in some language and runs it.
For example, a C compiler typically translates C source code (the input language) to an assembly language program (the output language). The assembler then takes the assembly language program and produces machine language. Once you have your output, you don't need the translators to run your program. Since you now have a machine language program, the CPU acts as the interpreter.
Many languages are implemented differently. For example, javac is a translator that converts Java source code to JVM bytecode. The JVM is an interpreter [1] that runs Java bytecode. After you run javac and get bytecode, you don't need javac anymore. However, whenever you want to run your program, you'll need the JVM.
The fact that translators don't need to be kept around to run a program is what makes it possible to "bootstrap" your language without having it end up running "on top of" layers and layers of other languages.
[1] Most JVMs do translation behind the scenes, but they're not really translators in that the interface to the JVM is not "input language -> output language".
Actually you can write in almost any language you like to. There's nothing that prevents you from writing a C compiler in Ruby. "All" you have to do is parse the program and emit the corresponding machine code. If you can read/write files, your programming language will probably suffice.
If you're starting from scratch on a new platform, you can do cross-compiling: write a compiler for your new platform, that runs in Java or natively on x86. Develop on your PC and then transfer the program to your new target platform.
The most basic compilers are probably Assembler and C.
Generally you can use just about whatever language you like. PHP was written in C, for example. If you have no access to any compiler whatsoever, you're going to have to resort to writing assembly language and compiling it to machine code by hand.
Many languages were first written in another available language and then reimplemented in itself and bootstrapped that way (or just kept the implementation in the foreign language, like PHP and perl), but some languages, like the first assembler was hand compiled to machine code like the first C-compiler was hand compiled to assembly.
I've been interested in bootstrapping ever since I read about it. To learn more I tried doing it myself by writing my own superset of BF, which i called EBF, in itself. the first version of EBF had 3 extra primitives and I hand compiled the first binary. I found a two step rhythm when doing so. I implemented a feature in the current language in one release and had a sweet release where I rewrote the code to utilize the implemented feature. The language was expressive enough to be used to make a LISP interpreter.
I have the hand compiled version together with the source in the first release tag and the code is quite small. The last version is 12 times bigger in size and the code and allows for more compact code so hand compiling the current version would be hard to get right.
Edmund Grimley Evans did something similar with his HEX language
One of the interesting things about doing this yourself is that you understand why some things are as they are. My code was product if small incremental adjustments an it looks more like it has evolved rather than been designed from scratch. I keep that in mind when reading code today which I think looks a little off.
Usually with a general-purpose programming language suitable for systems development, e.g. C, Haskell, ML, Lisp, etc., but the list of options is long. Also, usually with some domain-specific languages for language implementation, i.e. parser and lexical analyzer generators, intermediate languages like LLVM, etc. And probably some shell scripts, testing frameworks, and a build configuration system, e.g. autoconf.
Most compiler were wriiten C or a c like program if not c then assembly lang is the way to go However when writing a new lang from scratch and you do not have a macro lib or source code from a prototype language you have to define your own functions Now in What Language? You can just write a Form "of source code called psedocode to the machine it looks like a bnf grammar from the object oriented structured lang spec like Fortran basic algo lisp. So image writing a cross code resembling any of these language syntax That's psedo code
What are programming languages in general?
programming languages are a just a way to talk to computers. roughly speaking at first because computers could only understand zeros and ones (due to the fact that computers are made of transistors as switches which could only take two states, we call these two states 0 and 1) and working with 0,1 was hard for us as humans so computer scientists decided to do a one-to-one mapping from every instruction in binary(0,1) to a more human readable form which they called it assembly language.
for example if we had an instruction like:
11001101
in assembly it would be called:
LOAD_A 15
which means that load the content of register a into memory location 15. as i said it was just a convention like choosing 0 and 1 for two states of the transistors or anything else in the computer.in this way having a program with 50 instructions , remembering the assembly language would be easier . so the user would write the assembly code and some program (assembler in this case) would translate the codes to binary instructions or machine language as they call it.
but then with the computers getting improved every day there was room for more complicated programs with more instructions, say 10000.
in this case a one-to-one mapping like assembly wouldn't work, so other high level programming languages were created. they said for example if for a relation with I/O devices for printing something on the screen created by the user takes about 80 instructions , let us do something in here and we could package all this code into one library and call it for example printf and also create another program which could translate this printf in here to the related assembly code and from there the assembly would do the rest. so they call it compiler.
so now every user who wants to just print something on the screen he wouldn't have to write all the instructions in binary or assembly he just types printf("something") and all the programs like the compiler and assembler would do the rest. now later other longer codes would be packaged in the same way to just facilitate the work of other people as you see that you could just simplify a thousands line of code into one code in python and pack it for the use of other people.
so let's say that you have packed a lot of different codes in python and created a module(libray, package or anything that you want to call it) and you call that module mgh(just my name). now let's say we have created this mgh somehow that any one who says:
import mgh
mgh.connect(ip,port.data)...
could easily connect to a remote server with the ip and port number specified and send the data afterwards(or something like that). now people could do all of it using one single line, but what that happens is that a lot of codes are getting executed which have been retrieved from the mgh file. and packaging it has not been for speeding up the process of execution but rather facilitating other programmers works. so in here if someone wants to use your code first he should import the file and then the python interpreter would recognize all the code in it and so it could interpret the code.
now if you want to create a programming language and you want to execute it , first it needs a translation, for example let's say that you create a program which could understand the syntax and convert it to c , in this case after it has been translated to c , the rest would be taken care of , by the c compiler , then assembler , linker, ... .
even though you would have to pay the price of being slower since it has to be converted to c first.
now one other thing that you could do is to create a program which could translate all the code to the equivalent assembly language just like what happens with c but in this case the program could do it directly and from there the rest would be done by the linker. we know that this program is called compiler.
so what i am talking about is that, the only code that the system understands is 0,1 , so somehow you should convert you syntax to that, now in our operating systems a lot of different programs like assembler, linker and ... have been created to tell you that if you could convert your code to assembly they could take care of the rest or as i said you could even use other programming languages compilers by converting your code to that language.
Even further binary ,or assembly operations must be translated into functions, thats the assemblers/compilers job, then into object,from data and functions, if you don't have a source file to see" how these objects functionality should be represented in your language implementation ,Then you have to recognize "see" implement, or define your own functions ,procedures, and data structures, Which requires a lot of knowledge, you need to ask yourself what is a function.Your mind then becomes the language simulation.This Separate a Master programmer from the rest.
I too had this question few months back. And I read few articles and watched some videos which helped me to start writing my own language called soft. Its not complete yet but I learned a lot of stuff from this journey.
Basic things you should know is how compiler works when it has to execute a code snippet. Compiler has a lot of phases like lexical analysis, semantic analyzer, AST(Abstract Syntax Tree) etc.
What I did in my new language can be found here - http://www.singhajit.com/writing-a-new-programming-language/
If you are writing a language for first time then all the best and you have a long way to go.