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22692: additional notes on a couple of parameter expansion features

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Peter Stephenson 2006-09-14 09:03:16 +00:00
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@ -1,3 +1,8 @@
2006-09-14 Peter Stephenson <pws@csr.com>
* 22692: Doc/Zsh/expn.yo: additional notes on a couple of
parameter expansion features.
2006-09-13 Peter Stephenson <p.w.stephenson@ntlworld.com>
* 22705: Doc/Zsh/expn.yo, Src/prompt.c, Src/subst.c, Src/utils.c,

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Doc/Zsh/expn.yo
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@ -608,6 +608,14 @@ set, the string resulting from the expansion will be interpreted as a
pattern anywhere that is possible, such as in filename expansion and
filename generation and pattern-matching contexts like the right
hand side of the `tt(=)' and `tt(!=)' operators in conditions.
In nested substitutions, note that the effect of the tt(~) applies to the
result of the current level of substitution. A surrounding pattern
operation on the result may cancel it. Hence, for example, if the
parameter tt(foo) is set to tt(*), tt(${~foo//\*/*.c}) is substituted by
the pattern tt(*.c), which may be expanded by filename generation, but
tt(${${~foo}//\*/*.c}) substitutes to the string tt(*.c), which will not
be further expanded.
)
enditem()
@ -960,6 +968,16 @@ following steps take place where applicable at all levels of substitution.
Note that, unless the `tt((P))' flag is present, the flags and any subscripts
apply directly to the value of the nested substitution; for example, the
expansion tt(${${foo}}) behaves exactly the same as tt(${foo}).
At each nested level of substitution, the substituted words undergo all
forms of single-word substitution (i.e. not filename generation), including
command substitution, arithmetic expansion and filename expansion
(i.e. leading tt(~) and tt(=)). Thus, for example, tt(${${:-=cat}:h})
expands to the directory where the tt(cat) program resides. (Explanation:
the internal substitution has no parameter but a default value tt(=cat),
which is expanded by filename expansion to a full path; the outer
substitution then applies the modifier tt(:h) and takes the directory part
of the path.)
)
item(tt(2.) em(Parameter Subscripting))(
If the value is a raw parameter reference with a subscript, such as