#autoload

local mod
local -a funcs alts
local -a modules=( example mathfunc system )

for mod in $modules; do
  funcs=( ${${${(f)"$(zmodload -Fl zsh/$mod 2>/dev/null)"}:#^+f:*}##+f:} )
  alts+=( "module-math-functions.${mod}:math function from zsh/${mod}:compadd -S '(' $funcs" )
done

_alternative $alts