expression-parser | LISP-like structured expression parser | Parser library
kandi X-RAY | expression-parser Summary
kandi X-RAY | expression-parser Summary
LISP-like structured expression parser
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Top functions reviewed by kandi - BETA
- Process an expression
- Get the default language .
- Get instance of LanguageUtil .
- Set a language method .
- Get method .
- Check if a language exists
- Get a language value
expression-parser Key Features
expression-parser Examples and Code Snippets
Lines of Code : 45License : Permissive (Apache-2.0)
Copyset(
'+',
function(float $l, float $r) : float {
return $l + $r;
}
)
/*
* Define "-" (subtraction) function
*/
->set(
'-',
function(float $l, float $r) : float {
set(
'or',
function(bool $l, bool $r) : bool {
return $l || $r;
}
);
/*
* Create an expression parser based on the language
*/
$parser = new ExpressionParser(
$language
);
/*
* Evaluate an expression, composer update
composer test
Community Discussions
Trending Discussions on expression-parser
QUESTION
I was checking the version of Vue on my computer, and I noticed I have two different versions. What's wrong here?
I recently updated my Vue CLI to 3.10.0, and got a few errors popping up. I checked my npm packages, and discovered this other version of Vue 2.5.17.
...ANSWER
Answered 2019-Aug-07 at 02:53There is a significant difference between global and local installs. @vue/cli is latest at 3.10 (as of this writing) and is installed globally because it is run from the command line. vue is usually installed locally and versions can vary from project to project. The latest version of vue is 2.6.10 as of this writing. Unclear why you would have issues with create unless you did not uninstall the prior version of the cli:
"If you have the previous vue-cli (1.x or 2.x) package installed globally, you need to uninstall it first with npm uninstall vue-cli -g"
Ref: https://cli.vuejs.org/guide/installation.html
Some other quick reads:
https://flaviocopes.com/npm-packages-local-global/
https://nodejs.org/en/blog/npm/npm-1-0-global-vs-local-installation/
QUESTION
I'm trying to parse some expression. I started from impressive answers of llonesmiz and Sehe
I wanted to add some:
(1) defined parameters. These prams are given as map by another class. They may have no argument (integer) one or two :
- imf ---> $imf
- imf(1) ---> $imf(1)
- imf(1,2) ---> $imf(1,2)
I'm traying to fist get the parameter name "imf" an then its arguments if they exist (1), (2,2) ...
(2) defined function given as a map by another class. They may have one, two or three argument :
- cos(1) ---> cos(1)
- cross(imf(1),1) ---> cross($imf(1),1)
- fun3(1,2,1) ---> fun3(1,2,1)
custom_fold_directive.hpp
...ANSWER
Answered 2019-Apr-09 at 14:42Following sehe suggestions, I added rules for parameters and functions. For function I build 3 lists “qi::symbols” depending on the number of arguments. The parser works fine.
custom_fold_directive.hpp
QUESTION
I faced with situation described further. I have a SBT project with traditional catalog structure in which I would like to use this library. Problem occurring when I try to parse the string directly in the program.
...ANSWER
Answered 2018-May-25 at 16:07Looks like the library you're trying to use does not have a compatible Scala 2.12 jar available in public maven repository, see here.
That means that SBT imports the version of that library that expects Scala 2.11 to be used, so it fails when looking up classes that exist there and do not exist in 2.12.
Usually you'd use SBT's %% symbol to fetch the "right" version of a library (the one using the Scala version used in your build):
QUESTION
I know there are libs like boost.spirit or the expression parser from http://jamesgregson.blogspot.de/2012/06/mathematical-expression-parser-in-c.html and many others.
However, my expression is to be evaluated quite a lot of times inside a loop and it seems quite inefficient to run the parser every time.
Suppose my expression string is "exp(-0.5*(t-t_0)^2/(b^2))" (simple gaussian),
where t_0 and b are constants and only t (=time) varies within the loop.
instead of calling the parser millions of times, I'd like to be able to save the expression somehow into a function accepting one argument (for the variable t) which then evaluates the expression.
Do you have an idea know how this can be done or if it can be done at all?
...ANSWER
Answered 2017-Feb-27 at 16:25What you want to achieve is totally feasible. You can for instance build an AST (https://en.wikipedia.org/wiki/Abstract_syntax_tree) from the expression, where some nodes of the tree represent the variables.
Then, the evaluation of the expression for some values of the variables corresponds to the evaluation of that tree.
Actually, most parsers will produce such a tree internally and you may be able to find some library producing an AST for your need or you might want to code it yourself (see also https://en.wikipedia.org/wiki/Shunting-yard_algorithm). Here is a simple example of an expression parser producing an AST (in Java though).
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