pip_services4_expressions

Description:

pip services4 expressions

Tokenizers, parsers and expression calculators in Dart #
This module is a part of the Pip.Services polyglot microservices toolkit.
It provides syntax and lexical analyzers and expression calculator optimized for repeated calculations.
The module contains the following packages:

Calculator - Expression calculator
CSV - CSV tokenizer
IO - input/output utility classes to support lexical analysis
Mustache - Mustache templating engine
Tokenizers - lexical analyzers to break incoming character streams into tokens
Variants - dynamic objects that can hold any values and operators for them

Quick links:

API Reference
Change Log
Get Help
Contribute

Use #
Add this to your package's pubspec.yaml file:
dependencies:
pip_services4_expressions: version
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Now you can install package from the command line:
pub get
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The example below shows how to use expression calculator to dynamically
calculate user-defined expressions.
import 'package:pip_services4_expressions/src/calculator/calculator.dart';
import 'package:pip_services4_expressions/src/calculator/variables/variables.dart';
import 'package:pip_services4_expressions/src/variants/variants.dart';

...
var calculator = ExpressionCalculator();

calculator.expression = 'A + b / (5 - Max(-123, 1)*2)';

var vars = VariableCollection();
vars.add(Variable('A', Variant('1')));
vars.add(Variable('B', Variant(3)));

var result = await calculator.evaluateWithVariables(vars);
print('The result of the expression is ' +
result.asString); // The result of the expression is 11
...
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This is an example to process mustache templates.
import 'package:pip_services4_expressions/src/mustache/mustache.dart';

var mustache = MustacheTemplate();
mustache.template =
'Hello, {{{NAME}}}{{#ESCLAMATION}}!{{/ESCLAMATION}}{{#unless ESCLAMATION}}.{{/unless}}';
var result =
mustache.evaluateWithVariables({'NAME': 'Mike', 'ESCLAMATION': true});
print("The result of template evaluation is '" + result.toString() + "'");
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For development you shall install the following prerequisites:

Dart SDK 2
Visual Studio Code or another IDE of your choice
Docker

Install dependencies:
pub get
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Run automated tests:
pub run test
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Generate API documentation:
./docgen.ps1
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Before committing changes run dockerized build and test as:
./build.ps1
./test.ps1
./clear.ps1
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Contacts #
The library is created and maintained by Sergey Seroukhov and Danil Prisiazhnyi.
The documentation is written by Egor Nuzhnykh, Alexey Dvoykin, Mark Makarychev, Levichev Dmitry.