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| author | Kaz Kylheku <kaz@kylheku.com> | 2021-07-07 06:37:58 -0700 |
|---|---|---|
| committer | Kaz Kylheku <kaz@kylheku.com> | 2021-07-07 06:37:58 -0700 |
| commit | 7375b5a42a77eeb3ac3f085b3d026adbb93ad5a9 (patch) | |
| tree | 399d56dfe53a8ac4c9e89f6c75c6e447d2dacddd /txr.1 | |
| parent | 381ed03066f89602011d82892fe59d4dfff07e00 (diff) | |
| download | txr-7375b5a42a77eeb3ac3f085b3d026adbb93ad5a9.tar.gz txr-7375b5a42a77eeb3ac3f085b3d026adbb93ad5a9.tar.bz2 txr-7375b5a42a77eeb3ac3f085b3d026adbb93ad5a9.zip | |
with-resources: undocumented nil skip behavior.
Paul A. Patience discovered the hidden "feature" of
with-resourcers, that the three-argument form of the binding
(var init cleanup) causes the with-resources form to terminate
if init returns nil. The (var init) syntax doesn't generate
this logic.
* stdlib/with-resources.tl (with-resources): Do not emit the
when form unless <= 265 compatibility is in effect.
* tests/012/oop-mac.tl: New file.
* txr.1: Compat note added.
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 31 |
1 files changed, 29 insertions, 2 deletions
@@ -47841,6 +47841,14 @@ if no .metn body-form s are present. +.TP* Note: + +From its inception, until \*(TX 265, +.code with-resources +featured an undocumented behavior. Details are given in the +COMPATIBILITY section's Compatibility Version Values subsection, +in the notes for compatibility value 265. + .TP* "Example:" The following expression opens a text file and reads a line from it, @@ -47853,8 +47861,6 @@ immediately: (put-line l))) .brev - - .coNP Special variable @ *unhandled-hook* The .code *unhandled-hook* @@ -82755,6 +82761,27 @@ of these version values, the described behaviors are provided if is given an argument which is equal or lower. For instance .code "-C 103" selects the behaviors described below for version 105, but not those for 102. +.IP 265 +Until \*(TX 265, the +.code with-resources +macro exhibits an undocumented behavior: the three-element binding expression +.mono +.meti >> ( var < init << cleanup ) +.onom +immediately causes the +.code with-resources +form to terminate with a return value of +.code nil +if the +.meta init +form returns +.codn nil . +Neither the +.meta cleanup +in the same expression, nor any subsequent binding expressions or the body +of the construct, are evaluated. Prior cleanup forms are evaluated in +reverse order, as documented. A compatibility value of 265 or less restores +this behavior. .IP 262 Selection 262 compatibility restores a wrong behavior which existed between versions 191 and 262 due to a regression. The wrong behavior is that the |