[squeakland] How can I evaluate an Expression in Text

[Bert Freudenberg]

On 30.03.2011, at 23:28, Ricardo Moran wrote:

> Hi Steve, 
> 
> From a script of the text object you can write:
> 
> Compiler evaluate: self getCharacters.
> 
> and if the text contains a valid smalltalk expression it will work, otherwise it will throw an error. I don't remember exactly how to catch syntax errors, though. I did it for the spreadsheet object last year, but I wasn't sure if that's the right way.

Here's a textual script to do this with error handling. It needs a "result" variable of type Number, and a "valid" variable of type Boolean. 

eval
	[self setResult: (Compiler evaluate: self getCharacters) asNumber.
	self setValid: true]
		on: SyntaxErrorNotification , Error
		do: [self setValid: false]

See attached project.

> As for the format, I have no idea. Sorry.

Use asInteger, asFloat, or asFraction. But note that Etoys always displays numbers as floats. If you want to display a number as fraction, you would need to use something like

	self setCharacters: 0.75 asFraction asString

E.g.

	Float pi = 3.141592653589793
	Float pi asInteger = 3
	Float pi asFraction = (884279719003555/281474976710656)

- Bert -

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