On Tue, May 21, 2013 at 10:51 AM, Roland Mainz <[email protected]> wrote:
> Attached (as "astksh20130503_typeset_copy_operator001.diff.txt") is a
> small patch which provides a type-independent copy-by-name operator.
>
> Usage example:
> -- snip --
> # 1. copy float by name
> $ ksh -c 'float i=5.5 ; typeset -c j=i ; print $i $j'
> 5.5 5.5
>
> # 2. copy associative array by name
> $ ksh -c 'compound c=( typeset -A i=( [1]=4 [3]=5 [7]=6 ) ) ; typeset
> -c c.j=c.i ; print -v c'
> (
> typeset -A i=(
> [1]=4
> [3]=5
> [7]=6
> )
> typeset -A j=(
> [1]=4
> [3]=5
> [7]=6
> )
> )
> -- snip --
>
> The idea is to have a _generic_ and type-independent facility to
> _copy_ variables by _name_ (instead of j="$i" ... which is copy by
> value and doesn't work the same way for all objects).
Here is a small demo using the "objstack_t" type:
-- snip --
$ cat stk.sh
function _assert
{
integer line=$1
shift
print -u2 -f "ASSERT line=${line}: %q\n" "$@"
# exit 1
}
alias _assert='_assert $LINENO'
# stack of objects
typeset -T objstack_t=(
compound -a st
integer st_n=0
# push an object
# argument is the name of a variable which will
# be moved into the stack space
function pushobj
{
nameref obj=$1
typeset -m "_.st[$((_.st_n++))].obj=obj"
}
# copy an object into the stack
# argument is the name of a variable which will
# be copied into the stack space
function copyobjtostack
{
nameref obj=$1
typeset -c "_.st[$((_.st_n++))].obj=obj"
}
# print absolute variable name of object in head
function printhead
{
printf '%s%s\n' "${!_}" ".st[${_.st_n}].obj"
}
# pop an object and return it to the location
# specified by the variable name passed in
function popobj
{
nameref obj=$1
typeset -m "obj=_.st[$((--_.st_n))].obj"
# "obj" should be removed from _.st[_.st_n] by
# now... complain if there are any "leftovers"
s="$(typeset -p _.st[_.st_n].obj)"
[[ "$s" == '' ]] || \
_assert "_.st[_.st_n].obj == \"$s\""
# remove empty array node which was created
# when "pushobj" moved the obj into the array
[[ "$(typeset -p _.st[_.st_n])" != '' ]] || \
_assert "_.st[_.st_n] is gone"
unset _.st[_.st_n]
}
)
function main
{
compound c
objstack_t c.ost
# copy object foo twice on the stack
compound foo=( integer val=5 )
c.ost.copyobjtostack foo
c.ost.copyobjtostack foo
compound cthulhu
bool cthulhu.taken_souls=true
c.ost.copyobjtostack cthulhu
cthulhu.taken_souls=false
c.ost.copyobjtostack cthulhu
print -v c
return 0
}
set -o nounset
main
$ ~/bin/ksh stk.sh
(
objstack_t ost=(
typeset -l -i st_n=4
st[0]=(
obj=(
typeset -l -i val=5
)
)
st[1]=(
obj=(
typeset -l -i val=5
)
)
st[2]=(
obj=(
_Bool taken_souls=true
)
)
st[3]=(
obj=(
_Bool taken_souls=false
)
)
)
)
-- snip --
----
Bye,
Roland
--
__ . . __
(o.\ \/ /.o) [email protected]
\__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer
/O /==\ O\ TEL +49 641 3992797
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