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Topic: Title formatting help (Read 3596 times) previous topic - next topic
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Title formatting help

I was playing around with title formatting, and I wanted to use the XOR function for something extremely useful (that mortals would never understand).

So anyways, I played around with the function, but I couldn't get it to do what I wanted. I tried seeing what $xor(1,0) returned - It was not an integer, so I tried doing $if($xor(1,0),1,0), but that returned 0 (1,0 is supposed to return 1).

Is the function broken or am I not using it correctly? Thanks in advance for your helpful advice...

Title formatting help

Reply #1 –
0 and 1 are just string constants in TAGZ. String constants evaluate to false. Field references (using %x%, $info(), $meta(), or $extra()) evaluate to true if and only if the referenced field is present. In which situation the return value of a non-boolean function evaluates to true, depends on the function. Empty strings as arguments appear to be special.

Examples:

$if($num(0,2),true,false) -> false
$if($num(%tracknumber%,2),true,false) -> true iff tracknumber tag is present
$if($num(1,%tracknumber%),true,false) -> false
$if($not(),true,false) -> false
$if($not(bla),true,false) -> true

Any mortal can find that out with a little experimentation.

Title formatting help

Reply #2 –
I can't even get this simple statement to work:

$if($num(1),1,0) => 0

Title formatting help

Reply #3 –
Quote
I can't even get this simple statement to work:

$if($num(1),1,0) => 0


It does exactly what it should.

Title formatting help

Reply #4 –
Unless you need bitwise XOR, you can use a combination of $add and $mod.

Title formatting help

Reply #5 –
Ok, I don't understand much of this at all. Do you think you could just show me how to get 1 XOR 0 or 0 XOR 1 to return 1. That's really all I need.

Edit: Just wanted to make it clear that I'm not using any fields or anything - Just numbers.

Title formatting help

Reply #6 –
Assuming the input numbers will always be 0 or 1, or all you care about is the least significant bit:

$add(0,0) returns 0
$add(1,0) returns 1
$add(0,1) returns 1
$add(1,1) returns 2

Throw $mod(,2) around that $add(), and the 2 becomes 0. Nice and simple... sort of.

Title formatting help

Reply #7 –
Thanks, but why doesn't the $xor function work properly?

Title formatting help

Reply #8 –
Quote
Thanks, but why doesn't the $xor function work properly?

It does, when you know how it is supposed to work. It does not perform a bitwise exclusive or of its arguments, rather it performs a logical xor of two truth values. Unfortunately, TAGZ has its own special rules about what is regarded as true and false. For example, it treats the numerical constants 0 and 1 as false.

Moreover, the logical operators in TAGZ return boolean values, with have no printable representation; they are printed as an empty string.

If you want to perform boolean arithmetic with the numbers 0 and 1, you have to simulate this using the arithmetic functions on integers. If a and b are either 0 or 1, you can use the following idioms:

$mod($add(a,b)) -- xor (as described by kode54)
$max(a,b) -- or
$min(a,b) or $mul(a,b) -- and
$sub(1,a) -- not

Title formatting help

Reply #9 –
Is it not possible to cast between types of values using TagZ?

Quote
$mod($add(a,b)) -- xor (as described by kode54)
$max(a,b) -- or
$min(a,b) or $mul(a,b) -- and
$sub(1,a) -- not


Thanks, that was helpful.