thereadme/mathexpr
1
0
Fork 0
Code Issues 1 Pull Requests Projects Releases Wiki Activity

initial commit

Browse Source
This commit is contained in:
Mahdi Dibaiee 2016-11-03 01:42:22 +03:30
commit 13b74b03f3
7 changed files with 366 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
.gitignore vendored Normal file
View File

@ -0,0 +1,23 @@
#### joe made this: http://goel.io/joe
#### haskell ####
dist
dist-*
cabal-dev
*.o
*.hi
*.chi
*.chs.h
*.dyn_o
*.dyn_hi
.hpc
.hsenv
.cabal-sandbox/
cabal.sandbox.config
*.prof
*.aux
*.hp
*.eventlog
.stack-work/
cabal.project.local
.HTF/

101
LICENSE Normal file
View File

@ -0,0 +1,101 @@
GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
The GNU General Public License is a free, copyleft license for
software and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program--to make sure it remains free
software for all its users. We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to
any other work released this way by its authors. You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.
To protect your rights, we need to prevent others from denying you
these rights or asking you to surrender the rights. Therefore, you have
certain responsibilities if you distribute copies of the software, or if
you modify it: responsibilities to respect the freedom of others.
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must pass on to the recipients the same
freedoms that you received. You must make sure that they, too, receive
or can get the source code. And you must show them these terms so they
know their rights.
Developers that use the GNU GPL protect your rights with two steps:
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.
For the developers' and authors' protection, the GPL clearly explains
that there is no warranty for this free software. For both users' and
authors' sake, the GPL requires that modified versions be marked as
changed, so that their problems will not be attributed erroneously to
authors of previous versions.
Some devices are designed to deny users access to install or run
modified versions of the software inside them, although the manufacturer
can do so. This is fundamentally incompatible with the aim of
protecting users' freedom to change the software. The systematic
pattern of such abuse occurs in the area of products for individuals to
use, which is precisely where it is most unacceptable. Therefore, we
have designed this version of the GPL to prohibit the practice for those
products. If such problems arise substantially in other domains, we
stand ready to extend this provision to those domains in future versions
of the GPL, as needed to protect the freedom of users.
Finally, every program is threatened constantly by software patents.
States should not allow patents to restrict development and use of
software on general-purpose computers, but in those that do, we wish to
avoid the special danger that patents applied to a free program could
make it effectively proprietary. To prevent this, the GPL assures that
patents cannot be used to render the program non-free.
The precise terms and conditions for copying, distribution and
modification follow.
TERMS AND CONDITIONS
0. Definitions.
"This License" refers to version 3 of the GNU General Public License.
"Copyright" also means copyright-like laws that apply to other kinds of
works, such as semiconductor masks.
"The Program" refers to any copyrightable work licensed under this
License. Each licensee is addressed as "you". "Licensees" and
"recipients" may be individuals or organizations.
To "modify" a work means to copy from or adapt all or part of the work
in a fashion requiring copyright permission, other than the making of an
exact copy. The resulting work is called a "modified version" of the
earlier work or a work "based on" the earlier work.
A "covered work" means either the unmodified Program or a work based
on the Program.
To "propagate" a work means to do anything with it that, without
permission, would make you directly or secondarily liable for
infringement under applicable copyright law, except executing it on a
computer or modifying a private copy. Propagation includes copying,
distribution (with or without modification), making available to the
public, and in some countries other activities as well.
To "convey" a work means any kind of propagation that enables other
parties to make or receive copies. Mere interaction with a user through
a computer network, with no transfer of a copy,

41
README.md Normal file
View File

@ -0,0 +1,41 @@
mathexpr
========
Ever wanted to take as input a mathematical expression to fill in values and use it? `mathexpr` is exactly what you need.
_I also wrote this in JavaScript some time ago: [Equation](https://github.com/mdibaiee/Equation)_
Examples
--------
Simple evaluation of expressions:
```haskell
import Data.MathExpr
main = do
expr <- getLine -- a mathematical expression, e.g. sin x + y ^ 2
-- replace x and y with the specified values and evaluate: sin 2 + 5 ^ 2 = 25.909..
print $ evaluate def expr [("x", 2), ("y", 5)]
```
Using custom operators and functions:
```haskell
import Data.MathExpr
-- operators are in the form (character, precedence, function)
-- example: ('+', 0, (+)), ('*', 1, (*))
-- the function should have the type (Double -> Double -> Double)
-- the higher the precedence, the sooner the operator operates
-- functions are in the form (name, function)
-- example: ("ln", log)
-- the function should have the type (Double -> Double)
main =
let avg a b = (a + b) / 2
let settings = Settings { operators = defaultOperators ++ [('~', 0, avg)]
, functions = defaultFunctions ++ [("trunc", fromIntegral . truncate)]
evaluate settings "3 ~ 5" [] -- 4
evaluate settings "trunc 1.1" [] -- 1
```

2
Setup.hs Normal file
View File

@ -0,0 +1,2 @@
import Distribution.Simple
main = defaultMain

25
mathexpr.cabal Normal file
View File

@ -0,0 +1,25 @@
name: mathexpr
version: 0.1.0.0
synopsis: Parse and evaluate math expressions with variables and functions
description: A simple tool to evaluate math expressions as strings with support for custom functions and operators
homepage: https://github.com/mdibaiee/mathexpr
license: GPL-3
license-file: LICENSE
author: Mahdi Dibaiee
maintainer: mdibaiee@aol.com
copyright: 2016 Mahdi Dibaiee
category: Math
build-type: Simple
-- extra-source-files:
cabal-version: >=1.10
library
hs-source-dirs: src
exposed-modules: Data.MathExpr
build-depends: base >= 4.7 && < 5,
data-default-class
default-language: Haskell2010
source-repository head
type: git
location: https://github.com/mdibaiee/mathexpr

108
src/Data/MathExpr.hs Normal file
View File

@ -0,0 +1,108 @@
module Data.MathExpr
( evaluate
, Settings (..)
, defaultFunctions
, defaultOperators
) where
import Data.Default.Class
import Data.Maybe (isJust, fromJust)
import Debug.Trace
import Data.List (find)
data Settings = Settings { operators :: [(Char, Int, Double -> Double -> Double)]
, functions :: [(String, Double -> Double)]
}
defaultOperators = [
('+', 0, (+)), ('-', 0, (-)),
('*', 1, (*)), ('/', 1, (/)),
('^', 2, (**))
]
defaultFunctions = [("ln", log), ("sin", sin), ("cos", cos)]
instance Default Settings where
def = Settings { operators = defaultOperators
, functions = defaultFunctions
}
toPostfix :: Settings -> String -> String
toPostfix settings s = helper (tokenize s) [] []
where
ops = operators settings
fns = functions settings
helper :: [String] -> [String] -> String -> String
helper [] os out = out ++ concat os
helper (c:cs) os out
| head c == '(' = helper cs (c:os) out
| head c == ')' && head os == "(" = helper cs (tail os) out
| head c == ')' = helper (c:cs) (tail os) (out ++ pad (head os))
| isOperator c && (null os || precedence c > precedence (head os)) = helper cs (c:os) out
| isOperator c = helper (c:cs) (tail os) (out ++ pad (head os))
| otherwise = helper cs os (out ++ pad c)
isOperator cs = isOp cs || isFunction cs
isOp cs = isJust $ (head cs) `triLookup` ops
isFunction cs = isJust $ cs `lookup` fns
precedence cs
| isFunction cs = Just 999
| otherwise = (head cs) `triLookup` ops
tokenize :: String -> [String]
tokenize str = words $ helper str
where
helper :: String -> String
helper [] = []
helper (c:cs)
| isAlphanumeric c = c : helper cs
| isSymbol c = pad [c] ++ helper cs
replaceVariables :: String -> [(String, Double)] -> String
replaceVariables str [] = str
replaceVariables str vars = concatMap replace (tokenize str)
where
replace c
| isVariable c = pad $ show $ fromJust $ c `lookup` vars
| otherwise = c
isVariable c = isJust $ c `lookup` vars
-- | Evaluate an expression
-- Example: `evaluate def "x + y ^ 2" [("x", 1), ("y", 2)]
evaluate :: Settings -> String -> [(String, Double)] -> Double
evaluate settings expr vars =
let postfix = toPostfix settings expr
replaced = replaceVariables postfix vars
in helper (tokenize replaced) []
where
ops = operators settings
fns = functions settings
helper :: [String] -> [String] -> Double
helper [] [o] = read o
helper (c:cs) os
| isOperator c =
let result = (operatorFunction c) (read . head . tail $ os) (read . head $ os)
in helper cs $ (show result) : drop 2 os
| isFunction c =
let result = (function c) (read . head $ os)
in helper cs $ (show result) : tail os
| otherwise = helper cs (c:os)
isOperator cs = isJust $ (head cs) `triLookup` ops
isFunction cs = isJust $ cs `lookup` fns
function cs = fromJust $ cs `lookup` fns
operatorFunction cs = case find (\(a, _, _) -> a == head cs) ops of
Just (_, _, c) -> c
Nothing -> const (const 0)
isParen cs = head cs `elem` ['(', ')']
alphanumeric = '.' : ['a'..'z'] ++ ['0'..'9']
isAlphanumeric = (`elem` alphanumeric)
isSymbol = not . (`elem` alphanumeric)
triLookup :: (Eq a) => a -> [(a, b, c)] -> Maybe b
triLookup a x = lookup a $ map (\(a, b, _) -> (a, b)) x
pad :: String -> String
pad x = ' ' : x ++ [' ']

66
stack.yaml Normal file
View File

@ -0,0 +1,66 @@
# This file was automatically generated by 'stack init'
#
# Some commonly used options have been documented as comments in this file.
# For advanced use and comprehensive documentation of the format, please see:
# http://docs.haskellstack.org/en/stable/yaml_configuration/
# Resolver to choose a 'specific' stackage snapshot or a compiler version.
# A snapshot resolver dictates the compiler version and the set of packages
# to be used for project dependencies. For example:
#
# resolver: lts-3.5
# resolver: nightly-2015-09-21
# resolver: ghc-7.10.2
# resolver: ghcjs-0.1.0_ghc-7.10.2
# resolver:
# name: custom-snapshot
# location: "./custom-snapshot.yaml"
resolver: lts-7.7
# User packages to be built.
# Various formats can be used as shown in the example below.
#
# packages:
# - some-directory
# - https://example.com/foo/bar/baz-0.0.2.tar.gz
# - location:
# git: https://github.com/commercialhaskell/stack.git
# commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
# extra-dep: true
# subdirs:
# - auto-update
# - wai
#
# A package marked 'extra-dep: true' will only be built if demanded by a
# non-dependency (i.e. a user package), and its test suites and benchmarks
# will not be run. This is useful for tweaking upstream packages.
packages:
- '.'
# Dependency packages to be pulled from upstream that are not in the resolver
# (e.g., acme-missiles-0.3)
extra-deps: []
# Override default flag values for local packages and extra-deps
flags: {}
# Extra package databases containing global packages
extra-package-dbs: []
# Control whether we use the GHC we find on the path
# system-ghc: true
#
# Require a specific version of stack, using version ranges
# require-stack-version: -any # Default
# require-stack-version: ">=1.1"
#
# Override the architecture used by stack, especially useful on Windows
# arch: i386
# arch: x86_64
#
# Extra directories used by stack for building
# extra-include-dirs: [/path/to/dir]
# extra-lib-dirs: [/path/to/dir]
#
# Allow a newer minor version of GHC than the snapshot specifies
# compiler-check: newer-minor