Automatically establishing new floattype

Question

Inside a macro I would like to establish a new type of float. One of the parameters to be set during that process is \ftype@TYPE, where TYPE is the float type: figure, table, and so on. I know, that \ftype@figure = 1 and \ftype@table = 2 normally are already set in the classes, e.g. report.cls, and I know, that each following float type gets a number, that is double the one before, so the next one would be 4, then 8, then 16 and so on.

What I don't know, though: How can one inside a macro find out, which is the highest float type number already in use -- for not using one twice?

Answer 1

Unfortunately latex does not provide a good answer here. Effectively the float package provides a standard \newfloat allocator but it has to guess the initial state, if you load it after floats other than figure and table are defined then they will be over-written by \newfloat.

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If you don't want to force float to be loaded then I would suggest

a) test if \newfloat is defined, and if so use it.

b) if it is not defined set a value to 1 then test the usual suspects and double the value each time one is defined, to get the free number so perhaps test \c@figure\c@table\c@listings\c@algorithm

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listings package does a simpler version of the same idea with

\AtBeginDocument{%
\@ifundefined{c@float@type}%
    {\edef\ftype@lstlisting{\ifx\c@figure\@undefined 1\else 4\fi}}
    {\edef\ftype@lstlisting{\the\c@float@type}%
     \addtocounter{float@type}{\value{float@type}}}%
}

so if \newfloat is defined in the preamble it uses the next free number from that allocation, otherwise hope for the best and use 1 or 4 depending whether figures are defined or not.