Re: inconsistencies between arithmetic and boolean operators

["Kristofer Karlsson" <kristofer.karlsson@...>]

I for one feel that the automatic type conversion is annoying, unnecessary and only serves to introduce unwanted behaviour instead of runtime errors (i.e. bugs), so my suggestion would instead be to remove all automatic type conversion.

2007/8/10, Adrien de Croy <adrien@qbik.com>:

As work on __cast progresses, I've come across an issue relating to
boolean operators.

Arithmetic operators attempt to convert both operands to a number first,
so they work fine with __cast.

boolean operators insist however that the 2 operands have the same type,
else the result is zero.  This is checked first.

This means that the following code

var1 = "3";
var2 = var1 * 2;

is valid and var2 will have the numeric value of 6

however

var1 = "3"
if(var1 < 4) then
...

is invalid, since var1 and 4 have different types, the result is an
error.  If you wanted this to "work" you'd need to write

var1 = "3"
if((var1 * 1) < 4) then
...

the multiplication converts var1 in-place to a number.

Shouldn't the boolean operators try and do something like this?

e.g. instead of simply returning false on a type mismatch, try (e.g. by
__cast metamethod) to demote the higher type to the lower type, where
the precedence of types is (in descending order)

TABLE
USERVALUE
STRING
NUMBER
BOOLEAN


Adrien

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