Re: deferred evaulation of function calls

[Robert P. J. Day]

On Thu, 27 May 2004, Noel Yap wrote:

> ':=' evaluates the RHS at the time of the assignment.  '=' evaluates the
> RHS at the time of actual use.

but in my original post, i did mention that my tests seemed to show no
difference.  here's a sample makefile i used, in a directory with at least 
a couple of .o files:

--------------------

.PHONY: main t1 t2 clean

imm := $(wildcard *.o)
def = $(wildcard *.o)

main:   t1 clean t2

t1:
        @echo imm = ${imm}
        @echo def = ${def}

clean:
        rm *.o

t2:
        @echo imm = ${imm}
        @echo def = ${def}

---------------------

  this is invoked in a directory with some object (*.o) files.  based on 
what you just said, what do you expect as the output?  i got the 
following:

imm = a.o b.o
def = a.o b.o
rm *.o
imm = a.o b.o
def = a.o b.o  ????? why?

  given that "def" was a deferred assignment, i would have thought that 
its second value would be the empty string since, at the "time of actual 
use", as you put it, there are no .o files left.

  or am i misreading something?

rday