flutter_exprtk

Description:

flutter exprtk

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, Web and Windows
To install #
dependencies:
flutter:
sdk: flutter

flutter_exprtk: ^0.0.9
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Import the library:
import 'package:flutter_exprtk/flutter_exprtk.dart';
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Web Platform: #
Web is supported by a wasm module, injected at runtime and adds roughly 1.2MB to your app
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();
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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();
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In a separate Isolate:
// Static or global function:
Future<List<double>> 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<double> 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");
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Handling errors #
new Expression() will throw an "InvalidExpressionException" if the expression isn't valid.
A ClearedExpressionException will be thrown if an expression has been cleared.
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
} on ClearedExpressionException {
// ... handle exception
}
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