I am trying to implement some AI planning algorithms in C, but got stuck with the basic concept :)
Before jumping to the main problem, I tried implementing some small framework that would support propositional logic:
FORMULA f = PROPOSITION(a + 3 > 0);
FORMULA g = PROPOSITION(is_smaller_than(b, c));
f = AND(NOT(f), g);
Now, the problem is that I would like not to evaluate the expressions like 'a + 3 > 0' at the moment of defining the formula, but in some later phase:
bool res = EVALUATE(f);
I guess closures would have been handy in this case, but unfortunately I also like to stick to C99.
Any idea ?
How about extending this to predicate logic ?
The final goal (ideally) would be to build an AI planning library, which can be directly plugged-in to the application, and not to receive the problem as STRIPS program strings.
Thanks
OK,
As commented above I have solved the issue by using a structure with method pointer and data in it. This is the most common way of simulating closures in C.
My implementation is available here:
https://github.com/pmilosev/clumsy
Related
I would like to convert the following to Hy, but I can't seem to figure out how to do it; is there perhaps a way to convert a string of python code to the hy syntax? I don't know if py would work because the evaluated result of f_back may not be safe.
import ast, inspect
def test(f_back):
return ast.literal_eval(f"inspect.currentframe(){'.f_back' * f_back}")
You could always evaluate x = x.f_back repeatedly in a loop instead of using metaprogramming for this.
To address the more general question, Hy itself only implements the Hy-to-Python direction, not Python to Hy. There's Hikaru Ikuta's py2hy, which doesn't work with recent releases of Hy, but he's recently talked about updating it, so that may change soon.
This is a trivial question, unsure if I should really be asking here, but would like to see if anyone has a more elegant way to write this in ruby.
I have a version string of format x.y.z or x.y or x. I would like a simple elegant way to convert this into an array where default 0 value is inserted if segment is missing. I have a few different ways to do this, but I was hoping for something a bit cleaner. Atm my current solution is this
version_string.split('.').each_with_index.with_object(['0','0','0']) { |(segment, i), version_array| version_array[i] = segment }
Seems to work fine, and I can always move to a simple method call to make code look cleanup, but something about the use of each_with_index and `with_object kinda bugs me. Just curious to see if rest of Ruby community have anything to add
How about (min Ruby 2.6)
version_string.split('.').then { |x, y = '0', z = '0'| [x,y,z] }
I am working on a port of some IDL code to Python (3.7). I have a translation working which uses whatever direct Python alternatives are available, and supplementing what I can with idlwrap. In an effort to eliminate legacy IDL functions from the code, I am looking for an alternative to ARRAY_INDICES(). Right now, I have simply translated the entire function directly and import it on its own. I've spent a good deal of time trying to understand exactly what it does, and even after translating it verbatim, it is still unclear to me, which makes coming up with a simple Python solution challenging.
The good news is I only need it to work with one specific set of arrays whose shapes wont change. An example of the code that will be run follows:
temp = np.sum(arr, axis=0)
goodval = idlwrap.where(temp > -10)
ngood = goodval.size
arr2 = np.zeros_like(arr)
for i in range(0, ngood - 1):
indices = array_indices(arr2, goodval[i])
#use indices for computation
Trying to implement something like this:
arr = (1..10)
arr[2,5] = [2,3,4,5]
arr(2,5] = [3,4,5]
arr[2,5) = [2,3,4]
arr(2,5) = [3,4]
Well, we need to override four bracket opreators: [], [), (], ()
Any ideas?
It's called "Including or excluding" in mathematics. https://en.wikipedia.org/wiki/Interval_(mathematics)#Including_or_excluding_endpoints
In short, this is not possible with the current Ruby parser.
The slightly longer answer: You'd have to start by modifying parse.y to support the syntax you propose and recompile Ruby. This is of course not a terrible practical approach, since you'd have to do that again for every new Ruby version. The saner approach would be to start a discussion on ruby-core to see if there is sufficient interest for this to be made part of the language (probably not tbh).
Your wanted syntax is not valid for the Ruby parser, but it could be implemented in Ruby with the help of self-modifying code.
The source files need to be pre-processed. A simple regular expression can substitute your interval expressions with ordinary method syntax, i.e.
arr[2,5] -> interval_closed(arr,2,5)
arr(2,5] -> interval_left_open(arr,2,5)
arr[2,5) -> interval_right_open(arr,2,5)
arr(2,5) -> interval_open(arr,2,5)
The string holding the modified source can be evaluated and becomes part of the application just like a source file on the hard disk. (See instance_eval)
The usage of self-modifying code should be well justified.
Is the added value worth the effort and the complications?
Does the code have to be readable for other programmers?
Is the preprocessing practical? E.g. will this syntax occur in one or a few isolated files, or be spread everywhere?
I want to generate empty implementations of procedures defined in a header file. Ideally they should return NULL for pointers, 0 for integers, etc, and, in an ideal world, also print to stderr which function was called.
The motivation for this is the need to implement a wrapper that adapts a subset of a complex, existing API (the header file) to another library. Only a small number of the procedures in the API need to be delegated, but it's not clear which ones. So I hope to use an iterative approach, where I run against this auto-generated wrapper, see what is called, implement that with delegation, and repeat.
I've see Automatically generate C++ file from header? but the answers appear to be C++ specific.
So, for people that need the question spelled out in simple terms, how can I automate the generation of such an implementation given the header file? I would prefer an existing tool - my current best guess at a simple solution is using pycparser.
update Thanks guys. Both good answers. Also posted my current hack.
so, i'm going to mark the ea suggestion as the "answer" because i think it's probably the best idea in general. although i think that the cmock suggestion would work very well in tdd approach where the library development was driven by test failures, and i may end up trying that. but for now, i need a quicker + dirtier approach that works in an interactive way (the library in question is a dynamically loaded plugin for another, interactive, program, and i am trying to reverse engineer the sequence of api calls...)
so what i ended up doing was writing a python script that calls pycparse. i'll include it here in case it helps others, but it is not at all general (assumes all functions return int, for example, and has a hack to avoid func defs inside typedefs).
from pycparser import parse_file
from pycparser.c_ast import NodeVisitor
class AncestorVisitor(NodeVisitor):
def __init__(self):
self.current = None
self.ancestors = []
def visit(self, node):
if self.current:
self.ancestors.append(self.current)
self.current = node
try:
return super(AncestorVisitor, self).visit(node)
finally:
if self.ancestors:
self.ancestors.pop(-1)
class FunctionVisitor(AncestorVisitor):
def visit_FuncDecl(self, node):
if len(self.ancestors) < 3: # avoid typedefs
print node.type.type.names[0], node.type.declname, '(',
first = True
for param in node.args.params:
if first: first = False
else: print ',',
print param.type.type.names[0], param.type.declname,
print ')'
print '{fprintf(stderr, "%s\\n"); return 0;}' % node.type.declname
print '#include "myheader.h"'
print '#include <stdio.h>'
ast = parse_file('myheader.h', use_cpp=True)
FunctionVisitor().visit(ast)
UML modeling tools are capable of generating default implementation in the language of choice. Generally there is also a support for importing source code (including C headers). You can try to import your headers and generate source code from them. I personally have experience with Enterprise Architect and it supports both of these operations.
Caveat: this is an unresearched answer as I haven't had any experience with it myself.
I think you might have some luck with a mocking framework designed for unit testing. An example of such a framework is: cmock
The project page suggests it will generate code from a header. You could then take the code and tweak it.