comma in expr(), too many arguments

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I get the error(in vti): too many arguments
when I try to do something like expr("log(x,1/3)")
I am pretty sure it's because of the comma in the logarythm in base 1/3.
However I don't know how to get around this.

PS-I know I can write expr("log(x)/log(1/3)") but I don't have control over my user input.

Thank you

[tabsquare]

ok got that resolved by installing a correct ti-89 titanium emulator (tiemu)