It is possible to issue warnings from any code using the warning
function. In its most simple form, the warning
function takes a
string describing the warning as its input argument. As an example,
the following code controls if the variable ‘a’ is non-negative,
and if not issues a warning and sets ‘a’ to zero.
a = -1; if (a < 0) warning ("'a' must be non-negative. Setting 'a' to zero."); a = 0; endif -| 'a' must be non-negative. Setting 'a' to zero.
Since warnings aren't fatal to a running program, it is not possible
to catch a warning using the try
statement or something similar.
It is however possible to access the last warning as a string using the
lastwarn
function.
It is also possible to assign an identification string to a warning.
If a warning has such an ID the user can enable and disable this warning
as will be described in the next section. To assign an ID to a warning,
simply call warning
with two string arguments, where the first
is the identification string, and the second is the actual warning. Note
that warning IDs are in the format "NAMESPACE:WARNING-NAME". The namespace
"Octave" is used for Octave's own warnings. Any other string is available
as a namespace for user's own warnings.
Format the optional arguments under the control of the template string template using the same rules as the
printf
family of functions (see Formatted Output) and print the resulting message on thestderr
stream. The message is prefixed by the character string ‘warning: ’. You should use this function when you want to notify the user of an unusual condition, but only when it makes sense for your program to go on.The optional message identifier allows users to enable or disable warnings tagged by id. A message identifier is of the form "NAMESPACE:WARNING-NAME". Octave's own warnings use the "Octave" namespace (see doc-warning_ids). The special identifier ‘"all"’ may be used to set the state of all warnings.
If the first argument is ‘"on"’ or ‘"off"’, set the state of a particular warning using the identifier id. If the first argument is ‘"query"’, query the state of this warning instead. If the identifier is omitted, a value of ‘"all"’ is assumed. If you set the state of a warning to ‘"error"’, the warning named by id is handled as if it were an error instead. So, for example, the following handles all warnings as errors:
warning ("error");If the state is ‘"on"’, ‘"off"’, or ‘"error"’ and the third argument is ‘"local"’, then the warning state will be set temporarily, until the end of the current function. Changes to warning states that are set locally affect the current function and all functions called from the current scope. The previous warning state is restored on return from the current function. The "local" option is ignored if used in the top-level workspace.
Implementation Note: For compatibility with matlab, escape sequences (e.g., "\n" => newline) are processed in template regardless of whether template has been defined within single quotes as long as there are two or more input arguments. Use a second backslash to stop interpolation of the escape sequence (e.g., "\\n") or use the
regexptranslate
function.See also: warning_ids, lastwarn, error.
Query or set the last warning message. When called without input arguments, return the last warning message and message identifier. With one argument, set the last warning message to msg. With two arguments, also set the last message identifier.
The functions distributed with Octave can issue one of the following warnings.
Octave:abbreviated-property-match
Octave:abbreviated-property-match
warning is enabled.
Octave:array-to-scalar
Octave:array-to-scalar
warning is enabled, Octave will
warn when an implicit conversion from an array to a scalar value is
attempted.
By default, the Octave:array-to-scalar
warning is disabled.
Octave:array-to-vector
Octave:array-to-vector
warning is enabled, Octave will
warn when an implicit conversion from an array to a vector value is
attempted.
By default, the Octave:array-to-vector
warning is disabled.
Octave:assign-as-truth-value
Octave:assign-as-truth-value
warning is
enabled, a warning is issued for statements like
if (s = t) ...
since such statements are not common, and it is likely that the intent was to write
if (s == t) ...
instead.
There are times when it is useful to write code that contains
assignments within the condition of a while
or if
statement. For example, statements like
while (c = getc ()) ...
are common in C programming.
It is possible to avoid all warnings about such statements by
disabling the Octave:assign-as-truth-value
warning,
but that may also let real errors like
if (x = 1) # intended to test (x == 1)! ...
slip by.
In such cases, it is possible suppress errors for specific statements by writing them with an extra set of parentheses. For example, writing the previous example as
while ((c = getc ())) ...
will prevent the warning from being printed for this statement, while allowing Octave to warn about other assignments used in conditional contexts.
By default, the Octave:assign-as-truth-value
warning is enabled.
Octave:associativity-change
Octave:associativity-change
warning is
enabled, Octave will warn about possible changes in the meaning of
some code due to changes in associativity for some operators.
Associativity changes have typically been made for matlab
compatibility.
By default, the Octave:associativity-change
warning is enabled.
Octave:autoload-relative-file-name
Octave:autoload-relative-file-name
is enabled,
Octave will warn when parsing autoload() function calls with relative
paths to function files. This usually happens when using autoload()
calls in PKG_ADD files, when the PKG_ADD file is not in the same
directory as the .oct file referred to by the autoload() command.
By default, the Octave:autoload-relative-file-name
warning is enabled.
Octave:broadcast
Octave:built-in-variable-assignment
Octave:built-in-variable-assignment
warning is
enabled.
Octave:deprecated-keyword
Octave:deprecated-keyword
warning is enabled, a
warning is issued when Octave encounters a keyword that is obsolete and
scheduled for removal from Octave.
By default, the Octave:deprecated-keyword
warning is enabled.
Octave:divide-by-zero
Octave:divide-by-zero
warning is enabled, a
warning is issued when Octave encounters a division by zero.
By default, the Octave:divide-by-zero
warning is enabled.
Octave:fopen-file-in-path
Octave:fopen-file-in-path
warning is enabled.
Octave:function-name-clash
Octave:function-name-clash
warning is enabled, a
warning is issued when Octave finds that the name of a function
defined in a function file differs from the name of the file. (If
the names disagree, the name declared inside the file is ignored.)
By default, the Octave:function-name-clash
warning is enabled.
Octave:future-time-stamp
Octave:future-time-stamp
warning is enabled, Octave
will print a warning if it finds a function file with a time stamp
that is in the future.
By default, the Octave:future-time-stamp
warning is enabled.
Octave:glyph-render
Octave:glyph-render
warning is enabled.
Octave:imag-to-real
Octave:imag-to-real
warning is enabled, a warning is
printed for implicit conversions of complex numbers to real numbers.
By default, the Octave:imag-to-real
warning is disabled.
Octave:load-file-in-path
Octave:load-file-in-path
warning is enabled.
Octave:logical-conversion
Octave:logical-conversion
warning is enabled.
Octave:matlab-incompatible
Octave:matlab-incompatible
warning is disabled.
The –traditional or –braindead startup options for Octave may also
be of use, See Command Line Options.
Octave:md5sum-file-in-path
Octave:md5sum-file-in-path
warning is enabled.
Octave:missing-glyph
Octave:missing-glyph
warning is enabled.
Octave:missing-semicolon
Octave:missing-semicolon
warning is enabled, Octave
will warn when statements in function definitions don't end in
semicolons.
By default the Octave:missing-semicolon
warning is disabled.
Octave:mixed-string-concat
Octave:mixed-string-concat
warning is enabled, print a
warning when concatenating a mixture of double and single quoted strings.
By default, the Octave:mixed-string-concat
warning is disabled.
Octave:neg-dim-as-zero
Octave:neg-dim-as-zero
warning is enabled, print a warning
for expressions like
eye (-1)
By default, the Octave:neg-dim-as-zero
warning is disabled.
Octave:nested-functions-coerced
Octave:nested-functions-coerced
warning is enabled.
Octave:noninteger-range-as-index
Octave:noninteger-range-as-index
warning is enabled.
Octave:num-to-str
Octave:num-to-str
warning is enable, a warning is
printed for implicit conversions of numbers to their ASCII character
equivalents when strings are constructed using a mixture of strings and
numbers in matrix notation. For example,
[ "f", 111, 111 ] ⇒ "foo"
elicits a warning if the Octave:num-to-str
warning is
enabled. By default, the Octave:num-to-str
warning is enabled.
Octave:possible-matlab-short-circuit-operator
Octave:possible-matlab-short-circuit-operator
warning
is enabled, Octave will warn about using the not short circuiting
operators &
and |
inside if
or while
conditions. They normally never short circuit, but matlab always
short circuits if any logical operators are used in a condition. You
can turn on the option
do_braindead_shortcircuit_evaluation (1)
if you would like to enable this short-circuit evaluation in
Octave. Note that the &&
and ||
operators always short
circuit in both Octave and matlab, so it's only necessary to
enable matlab-style short-circuiting if it's too arduous to modify
existing code that relies on this behavior.
By default, the Octave:possible-matlab-short-circuit-operator
warning
is enabled.
Octave:precedence-change
Octave:precedence-change
warning is enabled, Octave
will warn about possible changes in the meaning of some code due to
changes in precedence for some operators. Precedence changes have
typically been made for matlab compatibility.
By default, the Octave:precedence-change
warning is enabled.
Octave:recursive-path-search
Octave:recursive-path-search
warning is enabled.
Octave:remove-init-dir
path
function changes the search path that Octave uses
to find functions. It is possible to set the path to a value which
excludes Octave's own built-in functions. If the
Octave:remove-init-dir
warning is enabled then Octave will warn
when the path
function has been used in a way that may render
Octave unworkable.
By default, the Octave:remove-init-dir
warning is enabled.
Octave:reload-forces-clear
Octave:reload-forces-clear
warning is enabled, Octave will
warn you when this happens, and print a list of the additional
functions that it is forced to clear.
By default, the Octave:reload-forces-clear
warning is enabled.
Octave:resize-on-range-error
Octave:resize-on-range-error
warning is enabled, print a
warning when a matrix is resized by an indexed assignment with
indices outside the current bounds.
By default, the ## Octave:resize-on-range-error
warning is disabled.
Octave:separator-insert
Octave:separator-insert
warning is disabled.
Octave:shadowed-function
Octave:shadowed-function
warning is enabled.
Octave:single-quote-string
Octave:single-quote-string
warning is disabled.
Octave:singular-matrix-div
Octave:singular-matrix-div
warning is enabled.
Octave:sqrtm:SingularMatrix
Octave:sqrtm:SingularMatrix
warning is enabled.
Octave:str-to-num
Octave:str-to-num
warning is enabled, a warning is printed
for implicit conversions of strings to their numeric ASCII equivalents.
For example,
"abc" + 0 ⇒ 97 98 99
elicits a warning if the Octave:str-to-num
warning is enabled.
By default, the Octave:str-to-num
warning is disabled.
Octave:undefined-return-values
Octave:undefined-return-values
warning is disabled,
print a warning if a function does not define all the values in
the return list which are expected.
By default, the Octave:undefined-return-values
warning is enabled.
Octave:variable-switch-label
Octave:variable-switch-label
warning is enabled, Octave
will print a warning if a switch label is not a constant or constant
expression.
By default, the Octave:variable-switch-label
warning is disabled.