Il 13/09/2013 15:43, Peter Maydell ha scritto: > On 25 August 2013 23:58, Ákos Kovács <akoskov...@gmx.com> wrote: >> lnot, land, lor, lif, eq, ne, isempty, notempty functions added >> Example usage: >> obj-$(call lor,$(CONFIG_LINUX),$(CONFIG_BSD)) += feature.o >> >> Signed-off-by: Ákos Kovács <akoskov...@gmx.com> > > Hi; I like the general idea here but I think there > are some issues with your implementation. > >> --- >> rules.mak | 16 ++++++++++++++++ >> 1 file changed, 16 insertions(+) >> >> diff --git a/rules.mak b/rules.mak >> index 4499745..7e8e3bd 100644 >> --- a/rules.mak >> +++ b/rules.mak >> @@ -106,6 +106,22 @@ clean: clean-timestamp >> obj := . >> old-nested-dirs := >> >> +# Logical functions > > I think we should be clear here about the input > and output ranges of these functions, ie that > the inputs should always be "y", "n" or "" (with > either "n" or the empty string being false). > >> +lnot = $(if $(subst n,,$1),n,y) >> + >> +land-yy = y >> +land = $(land-$1$2) > > This means that $(call land,y,n) would expand > to the empty string, not 'y' or 'n', right? > I think we should make all these functions always > expand to either 'y' or 'n'. > > land = $(if $(findstring yy,$1$2),y,n) > > will do this. > >> +lor = $(if $(subst $2,,$1)$(subst $1,,$2),n,y) > > This can't be correct for both 'lor' and 'eq'. > In fact it works as 'eq'. A working lor would be: > > lor = $(if $(findstring y,$1$2),y,n) > >> +lif = $(if $(subst n,,$1),$2,$3) >> + >> +eq = $(if $(subst $2,,$1)$(subst $1,,$2),n,y) >> +ne = $(if $(subst $2,,$1)$(subst $1,,$2),y,n) > > These give the wrong answer for comparisons > of 'n' with ''. Working versions: > > eq = $(if $(filter $(call lnot,$1),$(call lnot,$2)),y,n) > ne = $(if $(filter $(call lnot,$1),$(call lnot,$2)),n,y)
isempty/notempty are clearly string functions, where only the output is of the y/n form. Seeing Akos's implementation of isempty/notempty, I think the desired semantics for eq/ne/isempty/notempty are also those of string functions. I would call your functions leqv/lxor, not eq/ne. Your patch is fine if you either rename eq/ne like this, or revert them to Akos's version. Paolo >> +isempty = $(call eq,$1,) >> +notempty = $(call ne,$1,) > > These are wrong assuming we want 'n' eq '' semantics, > and we can directly implement them with $if anyway: > > isempty = $(if $1,n,y) > notempty = $(if $1,y,n)
