KernelFunctions is a Pine Script v5 library that exports kernel weight functions for Nadaraya-Watson style estimation. It calculates a Rational Quadratic kernel, a Gaussian kernel based on a radial basis function, and a periodic kernel that models repeating be
Library · Pine Script v5 · Library
StringEvaluation
This utility library evaluates mathematical expressions formatted as strings within Pine Script v5.
GitHub stars261on the repository
Pine versionv5runs as is
Lines of code254
Settings0inputs
LicenceNone statedfile: MPL-2.0
Last update4 years ago13 Nov 2021
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Source Code
254 lines of Pine Script v5 from beta/libs/StringEvaluation.pinescript, published under MPL-2.0 (file header). Keep the author's credit and licence lines when you reuse it.
// This source code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// © RicardoSantos
//@version=5
// @description Methods to handle evaluation of strings.
library(title='StringEvaluation')
// imports:
import RicardoSantos/MathOperator/1 as op
// Helper Functions:
// @function Check if char is a comma ".".
// @param char string, 1 character string.
// @returns bool.
export is_comma (string char) => //{
char == '.' ? true : false
//}
// @function Check if char is a operator.
// @param char string, 1 character string.
// @returns bool.
export is_op (string char) => //{
switch char
'+' => true
'-' => true
'*' => true
'/' => true
'^' => true
'%' => true
=> false
//}
// @function convert a single char string into valid number.
// @param char string, 1 character string.
// @returns float.
export number (string char) => //{
switch char
'0' => 0
'1' => 1
'2' => 2
'3' => 3
'4' => 4
'5' => 5
'6' => 6
'7' => 7
'8' => 8
'9' => 9
=> na
//}
// @function operation between left and right values.
// @param op string, operator string character.
// @param left float, left value of operation.
// @param right float, right value of operation.
export operator (string op, float left, float right) => //{
switch op
'+' => op.add(left, right)
'-' => op.subtract(left, right)
'*' => op.multiply(left, right)
'/' => op.divide(left, right)
'^' => math.pow(left, right)
'%' => op.remainder(left, right)
=> na
//}
// @function level of precedence of operator.
// @param op string, operator 1 char string.
// @returns int.
export operator_precedence (string op) => //{
switch op
'+' => 2
'-' => 2
'*' => 3
'/' => 3
'^' => 4
'%' => 3
=> 0
//}
// @function Evaluate a string to clean up and retrieve only used chars
// @param _str string, arithmetic operations in a string.
// @returns string array, evaluated array.
export cleanup (string _str) => //{
// remove spaces:
_unspaced = str.replace_all(source=_str, target=' ', replacement='')
_T0 = str.split(_unspaced, '')
// adds ( ) + - / * characters:
// join digit sequences into 1 whole number:
_T1 = array.new_string(0)
string _saved_expression = ''
for _i = 0 to array.size(id=_T0)-1
_current = array.get(id=_T0, index=_i)
if _current == '(' or _current == ')'
if _saved_expression != ''
array.push(id=_T1, value=_saved_expression)
array.push(id=_T1, value=_current)
_saved_expression := ''
if not na(operator(_current, 1, 1))
if _saved_expression != ''
array.push(id=_T1, value=_saved_expression)
array.push(id=_T1, value=_current)
_saved_expression := ''
if not na(number(_current)) or is_comma(_current)
_saved_expression := _saved_expression + _current
array.push(id=_T1, value=_saved_expression)
_T1
//{ usage:
// if barstate.islastconfirmedhistory
// label.new(bar_index, 0.0, str.tostring(cleanup('1+ 66* 7/2^2 %5 ')))
//}
// @function uses Shunting-Yard algorithm to generate a RPN (Reverse Polish notation)
// array of strings from a array of strings containing arithmetic notation.
// ex:.. '[3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3]' --> '[3 4 2 * 1 5 - 2 3 ^ ^ / +]'
// @param tokens string array, array with arithmetic notation.
// @returns
export generate_rpn (string[] tokens)=> //{
int _size = array.size(id=tokens)
if _size < 1
runtime.error('StringEvaluation -> generate_rpn(): "tokens" is empty.')
string[] _S = array.new_string(na)
else
_opstack = array.new_string(size=0)
_output = array.new_string(size=0)
for _i = 0 to _size-1
string _current_token = array.get(id=tokens, index=_i)
_current_arrified = str.split(_current_token, '')
int _current_size = array.size(id=_current_arrified)
if not na(number(array.get(id=_current_arrified, index=0)))
array.push(id=_output, value=_current_token)
else if _current_token == '('
array.push(id=_opstack, value=_current_token)
else if _current_token == ')'
int _size_stack = array.size(id=_opstack)
if _size_stack > 0
for _j = _size_stack-1 to 0
string _op = array.pop(id=_opstack)
if _op == '('
break
else
array.push(id=_output, value=_op)
else if is_op(_current_token)
int _size_stack = array.size(id=_opstack)
if _size_stack > 0
for _j = _size_stack-1 to 0
string _op = array.pop(id=_opstack)
int _op_precedence = operator_precedence(_op)
int _token_precedence = operator_precedence(_current_token)
if _op_precedence > _token_precedence or (_op_precedence == _token_precedence and _op != '^')
array.push(id=_output, value=_op)
else
array.push(id=_opstack, value=_op)
break
array.push(id=_opstack, value=_current_token)
int _size_stack = array.size(id=_opstack)
if _size_stack > 0
for _i = _size_stack-1 to 0
string _op = array.pop(id=_opstack)
if _op == '('
runtime.error('StringEvaluation -> generate_rpn(): mismatched parentesis!.')
else
array.push(id=_output, value=_op)
_output
//{ usage:
// if barstate.islastconfirmedhistory
// label.new(bar_index, 0.0, str.tostring(generate_rpn(cleanup('1+ 66* 7/2^2 %5 '))))
//{ reference:
// https://rosettacode.org/wiki/Parsing/Shunting-yard_algorithm
// https://en.wikipedia.org/wiki/Shunting-yard_algorithm
// https://brilliant.org/wiki/shunting-yard-algorithm/
//}}}
// @function evaluate a RPN (Reverse Polish notation) array of strings.
// ex:.. 3 4 2 * 1 5 - 2 3 ^ ^ / +
//| @param tokens string array, RPN ordered tokens, ex(['3', '4', '2', '1', '5', '2', '3', '*', '-', '^', '^', '/', '+']).
//| @returns float, solution.
export parse_rpn (string[] tokens) => //{
int _size = array.size(id=tokens)
if _size < 1
runtime.error('StringEvaluation -> generate_rpn(): "tokens" is empty.')
float(na)
else
float _solution = na
_stack = array.new_float()
for _i = 0 to _size-1
string _token = array.get(id=tokens, index=_i)
float _number = str.tonumber(_token)
if not na(_number)//
array.push(id=_stack, value=_number)
else
if array.size(id=_stack) > 1
// runtime.error('StringEvaluation -> generate_rpn(): insufficient operands!!.\n' + str.tostring(_stack))
// else
o2 = array.pop(id=_stack)
o1 = array.pop(id=_stack)
if is_op(_token)
float _op = operator(_token, o1, o2)
array.push(id=_stack, value=_op)
else
runtime.error('StringEvaluation -> generate_rpn(): unrecognized operator: (' + _token + ' ).')
_solution := array.pop(id=_stack)
_solution
//{ usage:
// if barstate.islastconfirmedhistory
// label.new(bar_index, 0.0, str.tostring(parse_rpn(generate_rpn(cleanup('((10+ 10 *30/20-50)%10)^2')))))
//{ reference:
// https://rosettacode.org/wiki/Parsing/RPN_calculator_algorithm
//}}}
// @function evaluate a string with references to a array of arguments.
//| @param tokens string, arithmetic operations with references to indices in arguments, ex:"0+1*0+2*2+3" arguments[1, 2, 3]
//| @param arguments float array, arguments.
//| @returns float, solution.
export eval (string tokens, float[] arguments) => //{
int _size_a = array.size(id=arguments)
if _size_a < 1
runtime.error('StringEvaluation -> generate_rpn(): "arguments" is empty.')
float(na)
else
string[] _tokens = generate_rpn(cleanup(tokens))
int _size_t = array.size(id=_tokens)
if _size_t < 1
runtime.error('StringEvaluation -> generate_rpn(): "tokens" is empty.')
float(na)
else
// calculate solution:
float _solution = na
_stack = array.new_float()
for _i = 0 to _size_t-1
string _token = array.get(id=_tokens, index=_i)
float _number = str.tonumber(_token)
if not na(_number)//
array.push(id=_stack, value=array.get(id=arguments, index=int(_number)))
else
if array.size(id=_stack) > 1
// runtime.error('StringEvaluation -> generate_rpn(): insufficient operands!!.\n' + str.tostring(_stack))
// else
o2 = array.pop(id=_stack)
o1 = array.pop(id=_stack)
if is_op(_token)
float _op = operator(_token, o1, o2)
array.push(id=_stack, value=_op)
else
runtime.error('StringEvaluation -> generate_rpn(): unrecognized operator: (' + _token + ' ).')
_solution := array.pop(id=_stack)
_solution
//{ usage:
if barstate.islastconfirmedhistory
label.new(bar_index, 0.0, str.tostring(eval('((0+ 0 *2/1-3)%0)^4', array.from(10.0, 20, 30, 50, 2))))
//{ reference:
// https://rosettacode.org/wiki/Parsing/RPN_calculator_algorithm
//}}}
Overview
StringEvaluation parses raw input strings, removes whitespace, extracts operators and numeric values, and handles operator precedence. The code includes support for transforming arithmetic expressions into Reverse Polish Notation via the Shunting-Yard algorithm. As a helper library, it contains no trading strategies, entry or exit signals, or user-configurable input settings. It draws nothing on the chart or in separate panes, operating purely as a mathematical parser for other indicators and scripts.
- String expression cleanup and parsing
- Arithmetic operator precedence handling
- Reverse Polish notation generation
- Shunting-Yard algorithm implementation
Details
Published by
ricardosantos79 on GitHub
Code credit
RicardoSantos, as written in the script's header
Type
Library, Pine Script v5
Draws
Library (no plots)
Markets
Any symbol
Timeframes
Any timeframe
Risk Notes
No repainting, lookahead or stacked entries were found in its code or README. That says nothing about how well it works: test it first.
Third-party code. ForexR did not write, test or endorse this script, and the summary above was generated automatically from its code and README. Indicators describe the past, and a strategy's backtest can look better than live trading, especially when a script repaints. Check it in the Strategy Tester and on a demo account before you rely on it.
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