How can I get the highest element in a CMake list?

I have a CMake list (literally or in a variable), and I want to obtain the list item with the maximum value. How should I do this?

Note: The list is not necessarily sorted, nor necessarily duplicate-free.

Starting CMake version 3.18 you should be able to use list(SORT) for getting a sorted list of elements making it simple to extract the maximum one. Perhaps not as efficient as a search through a list, but for the expected input sizes probably makes little difference:

function(max_element OUT_VAR)
	list(SORT ARGN COMPARE NATURAL ORDER DESCENDING)
	list(GET ARGN 0 MAX_ELEMENT)
	set(${OUT_VAR} ${MAX_ELEMENT} PARENT_SCOPE)
endfunction()

max_element(MAX 10 4 19 1)
message("MAX = ${MAX}") # prints "MAX = 19"

I don't know of a CMake command that gets you the maximum element, but you can write your own function for getting this:

function(max out_var)
    list(GET ARGN 0 ${out_var})
    list(SUBLIST ARGN 1 -1 tail)
    foreach(val ${tail})
        if (${val} GREATER ${out_var})
            set(${out_var} ${val})
        endif()
    endforeach()
    return(PROPAGATE ${out_var})
endfunction()

You invoke it like so:

max(out1 1 2 3 5 4 5 3)
# out1 is now "5"
set(my_list 7 3 5)
max(out2 ${my_list})
# out2 is now "7"

Further reading:

• CMake's list commands

• Writing CMake functions

• CMake's return command