Exception when define variable Number with character "e"

[QuangLM75]

Having my 'e' variable exception because of same name with exponential operation

void _expression_creation_and_evaluation() { Parser p = Parser(); Expression exp = p.parse('e'); ContextModel cm = ContextModel(); cm.variables = { 'e': Number(5.0), }; double eval = exp.evaluate(EvaluationType.REAL, cm); print('Expression: $exp'); print('Evaluated expression: $eval\n (with context: $cm)'); // = 1 }

The excetion thrown:

Unhandled exception: RangeError (index): Invalid value: Valid value range is empty: -1 #0 List.[] (dart:core-patch/growable_array.dart:264:36) #1 List.removeLast (dart:core-patch/growable_array.dart:336:20) #2 Parser.parse (package:math_expressions/src/parser.dart:78:44) #3 _expression_creation_and_evaluation (package:luklak_id_mobile/ui/pages/authorized/dashboard/gadgets/count_calculate/count.dart:23:22) #4 main (package:luklak_id_mobile/ui/pages/authorized/dashboard/gadgets/count_calculate/count.dart:11:3) #5 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297:19) #6 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:192:26)

[fkleon]

Hi @QuangLM75, thanks for your report.

This looks similar to #61 and #35 (including the linked issues there), and mostly stems from limitations of the current parser implementation.

Unfortunately I don't have an easy workaround except creating your expressions programmatically and not using the included parser interface.