This implementation is not nearly pure GNU Make enough for me. :)

Here’s one that is pure Make. Some of it is cribbed from The GNU Make Book and not all the definitions are necessary. Numbers are represented by a list of xs. So 5 would be the string x x x x x.

It counts down from 100 instead of up. I don’t really care.

_pow2 = $(if $1,$(foreach a,x x,$(call _pow2,$(wordlist 2,$(words $1),$1))),x x)
_all := $(call _pow2,1 2 3 4 5 6 7 8) 
num = $(words $1)
val = $(wordlist 1,$1,$(_all))
incr = x $1
decr = $(wordlist 2,$(words $1),$1)

max = $(subst xx,x,$(join $1,$2))
min = $(subst xx,x,$(filter xx,$(join $1,$2)))

eq = $(filter $(words $1),$(words $2))
ne = $(filter-out $(words $1),$(words $2))
gt = $(filter-out $(words $2),$(words $(call max,$1,$2)))
gte = $(call gt,$1,$2)$(call eq,$1,$2)
lt = $(filter-out $(words $1),$(words $(call max,$1,$2)))
lte = $(call lt,$1,$2)$(call eq,$1,$2)

add = $1 $2
subtract = $(if $(call gte,$1,$2),$(filter-out xx,$(join $1,$2)),$(warning Underflow))
multiply = $(foreach a,$1,$2)
divide = $(if $(call gte,$1,$2),x $(call divide,$(call subtract,$1,$2),$2),)
mod = $(if $(call gte,$1,$2),$(call mod,$(call subtract,$1,$2),$2),$1)

fizz = $(call eq,$(call val,0),$(call mod,$1,$(call val,3)))
buzz = $(call eq,$(call val,0),$(call mod,$1,$(call val,5)))
fizzbuzz = $(and $(call fizz,$1),$(call buzz,$1))

fbcheck = $(if $(call fizzbuzz,$1),$(info FizzBuzz),\
            $(if $(call fizz,$1),$(info Fizz),\
               $(if $(call buzz,$1),$(info Buzz),\
                   $(info $(call num,$1)))))

loop = $(if $1,$(call fbcheck,$1)$(call loop,$(call decr,$1)),)

all: ; @echo $(call loop,$(call val,100))

It relies on a specific and nonportable shell builtin.

I’ve been trying to think if this is doable in POSIX make, as underpowered as that is… sadly my make-fu is not strong enough. I don’t think it has those good functions in it.