flutter_exprtk
所属分类：Dart语言编程
开发工具：C++
文件大小：1949KB
下载次数：0
上传日期：2023-02-17 18:16:24
上 传 者：
sh-1993
说明： exprtk数学表达式解析器的dart-ffi包装器
(dart ffi wrapper for exprtk math expression parser)
文件列表:
.vscode (0, 2023-08-20)
.vscode\launch.json (2675, 2023-08-20)
.vscode\settings.json (1404, 2023-08-20)
CHANGELOG.md (250, 2023-08-20)
LICENSE (1066, 2023-08-20)
flutter_exprtk (0, 2023-08-20)
flutter_exprtk\.metadata (309, 2023-08-20)
flutter_exprtk\CHANGELOG.md (571, 2023-08-20)
flutter_exprtk\LICENSE (1035, 2023-08-20)
flutter_exprtk\analysis_options.yaml (51, 2023-08-20)
flutter_exprtk\example (0, 2023-08-20)
flutter_exprtk\example\.metadata (305, 2023-08-20)
flutter_exprtk\example\analysis_options.yaml (51, 2023-08-20)
flutter_exprtk\example\android (0, 2023-08-20)
flutter_exprtk\example\android\app (0, 2023-08-20)
flutter_exprtk\example\android\app\build.gradle (1708, 2023-08-20)
flutter_exprtk\example\android\app\src (0, 2023-08-20)
flutter_exprtk\example\android\app\src\debug (0, 2023-08-20)
flutter_exprtk\example\android\app\src\debug\AndroidManifest.xml (327, 2023-08-20)
flutter_exprtk\example\android\app\src\main (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\AndroidManifest.xml (2142, 2023-08-20)
flutter_exprtk\example\android\app\src\main\kotlin (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\kotlin\com (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\kotlin\com\example (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\kotlin\com\example\example (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\kotlin\com\example\example\MainActivity.kt (124, 2023-08-20)
flutter_exprtk\example\android\app\src\main\res (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\res\drawable-v21 (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\res\drawable-v21\launch_background.xml (438, 2023-08-20)
flutter_exprtk\example\android\app\src\main\res\drawable (0, 2023-08-20)
flutter_exprtk\example\android\app\src\main\res\drawable\launch_background.xml (434, 2023-08-20)
flutter_exprtk\example\android\app\src\main\res\mipmap-hdpi (0, 2023-08-20)
... ...
# flutter_exprtk
ffi wrapper for exprtk math expression parser
See https://github.com/ArashPartow/exprtk for details
## Limitations
Only works with doubles, not vectors etc.
Currently supports Android, MacOS, iOS and Windows
## To install
dependencies:
flutter:
sdk: flutter
flutter_exprtk: ^0.0.5
Import the library:
import 'package:flutter_exprtk/flutter_exprtk.dart';
## Getting Started
// Create a new expression
final exp = Expression(
expression: "a / b", // The expression
variables: { "a": 4, "b": 2 }, // variables
constants: {} // Optional constants can be omitted
);
// Get the value
print(exp.value); // -> 2
// Variables can be changed:
exp["a"] = 100
print(exp.value); // -> 50
exp["b"] = 50
print(exp.value); // -> 2
// Call clear to free up memory
expression.clear();
More complex example:
final exp2 = Expression(
expression: "clamp(-1.0,sin(2 * pi * x) + cos(x / 2 * pi),+1.0)",
variables: { "x": 0 }
);
for (double x = -5; x <= 5; x += 0.001)
{
exp2["x"] = x;
print("${exp2.value}");
}
// Call clear to free up memory
exp2.clear();
In a separate Isolate:
// Static or global function:
Future> computeExpression (dynamic _) async {
final exp2 = Expression(
expression: "clamp(-1.0,sin(2 * pi * x) + cos(x / 2 * pi),+1.0)",
variables: { "x": 0 }
);
final List results = [];
for (double x = -5; x <= 5; x += 0.001)
{
exp2["x"] = x;
results.add(exp2.value);
}
exp2.clear();
return results;
}
// Then run it for example with compute from flutter:foundation:
final results = await compute(computeExpression, null);
print("Results $results");
## Handling errors
new Expression() will throw an "InvalidExpressionException" if the expression isn't valid.
If you try to set a variable which hasn't been initialized an "UninitializedVariableException" will be thrown:
try {
final exp = Expression(
expression: "///////", // will cause an InvalidExpressionException
variables: {}
);
final exp = Expression(
expression: "a + b",
variables: { "c": 0 } // will cause an UninitializedVariableException
);
exp["d"] = 0; // will also cause an UninitializedVariableException
} on InvalidExpressionException {
// ... handle exception
} on UninitializedVariableException {
// ... handle exception
}
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