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@ -1586,7 +1586,8 @@ Each variable name may be postfixed by an attribute |
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@producname{attrib}@producbody{@bnfopt{@bnfter{<} @bnfNter{Name} @bnfter{>}}} |
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} |
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There are two possible attributes: |
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@id{const}, which declares a @x{constant variable}, |
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@id{const}, which declares a @emph{constant} or @emph{read-only} variable, |
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@index{constant variable} |
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that is, a variable that cannot be assigned to |
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after its initialization; |
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and @id{close}, which declares a to-be-closed variable @see{to-be-closed}. |
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@ -9118,7 +9119,7 @@ is a more portable solution. |
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@simplesect{ |
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Here we list the incompatibilities that you may find when moving a program |
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from @N{Lua 5.3} to @N{Lua 5.4}. |
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from @N{Lua 5.4} to @N{Lua 5.5}. |
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You can avoid some incompatibilities by compiling Lua with |
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appropriate options (see file @id{luaconf.h}). |
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@ -9155,51 +9156,6 @@ change between versions. |
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@itemize{ |
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@item{ |
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The coercion of strings to numbers in |
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arithmetic and bitwise operations |
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has been removed from the core language. |
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The string library does a similar job |
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for arithmetic (but not for bitwise) operations |
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using the string metamethods. |
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However, unlike in previous versions, |
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the new implementation preserves the implicit type of the numeral |
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in the string. |
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For instance, the result of @T{"1" + "2"} now is an integer, |
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not a float. |
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} |
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@item{ |
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Literal decimal integer constants that overflow are read as floats, |
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instead of wrapping around. |
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You can use hexadecimal notation for such constants if you |
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want the old behavior |
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(reading them as integers with wrap around). |
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} |
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@item{ |
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The use of the @idx{__lt} metamethod to emulate @idx{__le} |
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has been removed. |
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When needed, this metamethod must be explicitly defined. |
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} |
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@item{ |
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The semantics of the numerical @Rw{for} loop |
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over integers changed in some details. |
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In particular, the control variable never wraps around. |
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} |
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@item{ |
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A label for a @Rw{goto} cannot be declared where a label with the same |
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name is visible, even if this other label is declared in an enclosing |
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block. |
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} |
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@item{ |
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When finalizing an object, |
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Lua does not ignore @idx{__gc} metamethods that are not functions. |
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Any value will be called, if present. |
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(Non-callable values will generate a warning, |
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like any other error when calling a finalizer.) |
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} |
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} |
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@ -9210,39 +9166,6 @@ like any other error when calling a finalizer.) |
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@itemize{ |
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@item{ |
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The function @Lid{print} does not call @Lid{tostring} |
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to format its arguments; |
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instead, it has this functionality hardwired. |
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You should use @idx{__tostring} to modify how values are printed. |
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} |
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@item{ |
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The pseudo-random number generator used by the function @Lid{math.random} |
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now starts with a somewhat random seed. |
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Moreover, it uses a different algorithm. |
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} |
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@item{ |
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By default, the decoding functions in the @Lid{utf8} library |
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do not accept surrogates as valid code points. |
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An extra parameter in these functions makes them more permissive. |
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} |
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@item{ |
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The options @St{setpause} and @St{setstepmul} |
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of the function @Lid{collectgarbage} are deprecated. |
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You should use the new option @St{incremental} to set them. |
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} |
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@item{ |
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The function @Lid{io.lines} now returns four values, |
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instead of just one. |
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That can be a problem when it is used as the sole |
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argument to another function that has optional parameters, |
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such as in @T{load(io.lines(filename, "L"))}. |
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To fix that issue, |
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you can wrap the call into parentheses, |
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to adjust its number of results to one. |
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} |
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} |
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@ -9254,46 +9177,6 @@ to adjust its number of results to one. |
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@itemize{ |
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@item{ |
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Full userdata now has an arbitrary number of associated user values. |
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Therefore, the functions @id{lua_newuserdata}, |
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@id{lua_setuservalue}, and @id{lua_getuservalue} were |
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replaced by @Lid{lua_newuserdatauv}, |
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@Lid{lua_setiuservalue}, and @Lid{lua_getiuservalue}, |
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which have an extra argument. |
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For compatibility, the old names still work as macros assuming |
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one single user value. |
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Note, however, that userdata with zero user values |
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are more efficient memory-wise. |
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} |
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@item{ |
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The function @Lid{lua_resume} has an extra parameter. |
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This out parameter returns the number of values on |
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the top of the stack that were yielded or returned by the coroutine. |
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(In previous versions, |
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those values were the entire stack.) |
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} |
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@item{ |
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The function @Lid{lua_version} returns the version number, |
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instead of an address of the version number. |
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The Lua core should work correctly with libraries using their |
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own static copies of the same core, |
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so there is no need to check whether they are using the same |
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address space. |
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} |
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@item{ |
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The constant @id{LUA_ERRGCMM} was removed. |
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Errors in finalizers are never propagated; |
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instead, they generate a warning. |
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} |
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@item{ |
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The options @idx{LUA_GCSETPAUSE} and @idx{LUA_GCSETSTEPMUL} |
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of the function @Lid{lua_gc} are deprecated. |
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You should use the new option @id{LUA_GCINC} to set them. |
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} |
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} |
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Roberto Ierusalimschy
2 years ago