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| Next: <a href="Selecting-Guile-Pretty_002dPrinters.html#Selecting-Guile-Pretty_002dPrinters" accesskey="n" rel="next">Selecting Guile Pretty-Printers</a>, Previous: <a href="Types-In-Guile.html#Types-In-Guile" accesskey="p" rel="prev">Types In Guile</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> |
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| <hr> |
| <a name="Guile-Pretty-Printing-API-1"></a> |
| <h4 class="subsubsection">23.3.3.8 Guile Pretty Printing API</h4> |
| <a name="index-guile-pretty-printing-api"></a> |
| |
| <p>An example output is provided (see <a href="Pretty-Printing.html#Pretty-Printing">Pretty Printing</a>). |
| </p> |
| <p>A pretty-printer is represented by an object of type <gdb:pretty-printer>. |
| Pretty-printer objects are created with <code>make-pretty-printer</code>. |
| </p> |
| <p>The following pretty-printer-related procedures are provided by the |
| <code>(gdb)</code> module: |
| </p> |
| <dl> |
| <dt><a name="index-make_002dpretty_002dprinter"></a>Scheme Procedure: <strong>make-pretty-printer</strong> <em>name lookup-function</em></dt> |
| <dd><p>Return a <code><gdb:pretty-printer></code> object named <var>name</var>. |
| </p> |
| <p><var>lookup-function</var> is a function of one parameter: the value to |
| be printed. If the value is handled by this pretty-printer, then |
| <var>lookup-function</var> returns an object of type |
| <gdb:pretty-printer-worker> to perform the actual pretty-printing. |
| Otherwise <var>lookup-function</var> returns <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-pretty_002dprinter_003f"></a>Scheme Procedure: <strong>pretty-printer?</strong> <em>object</em></dt> |
| <dd><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:pretty-printer></code> object. |
| Otherwise return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-pretty_002dprinter_002denabled_003f"></a>Scheme Procedure: <strong>pretty-printer-enabled?</strong> <em>pretty-printer</em></dt> |
| <dd><p>Return <code>#t</code> if <var>pretty-printer</var> is enabled. |
| Otherwise return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dpretty_002dprinter_002denabled_0021"></a>Scheme Procedure: <strong>set-pretty-printer-enabled!</strong> <em>pretty-printer flag</em></dt> |
| <dd><p>Set the enabled flag of <var>pretty-printer</var> to <var>flag</var>. |
| The value returned is unspecified. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-pretty_002dprinters"></a>Scheme Procedure: <strong>pretty-printers</strong></dt> |
| <dd><p>Return the list of global pretty-printers. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dpretty_002dprinters_0021"></a>Scheme Procedure: <strong>set-pretty-printers!</strong> <em>pretty-printers</em></dt> |
| <dd><p>Set the list of global pretty-printers to <var>pretty-printers</var>. |
| The value returned is unspecified. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-make_002dpretty_002dprinter_002dworker"></a>Scheme Procedure: <strong>make-pretty-printer-worker</strong> <em>display-hint to-string children</em></dt> |
| <dd><p>Return an object of type <code><gdb:pretty-printer-worker></code>. |
| </p> |
| <p>This function takes three parameters: |
| </p> |
| <dl compact="compact"> |
| <dt>‘<samp>display-hint</samp>’</dt> |
| <dd><p><var>display-hint</var> provides a hint to <small>GDB</small> or <small>GDB</small> |
| front end via MI to change the formatting of the value being printed. |
| The value must be a string or <code>#f</code> (meaning there is no hint). |
| Several values for <var>display-hint</var> |
| are predefined by <small>GDB</small>: |
| </p> |
| <dl compact="compact"> |
| <dt>‘<samp>array</samp>’</dt> |
| <dd><p>Indicate that the object being printed is “array-like”. The CLI |
| uses this to respect parameters such as <code>set print elements</code> and |
| <code>set print array</code>. |
| </p> |
| </dd> |
| <dt>‘<samp>map</samp>’</dt> |
| <dd><p>Indicate that the object being printed is “map-like”, and that the |
| children of this value can be assumed to alternate between keys and |
| values. |
| </p> |
| </dd> |
| <dt>‘<samp>string</samp>’</dt> |
| <dd><p>Indicate that the object being printed is “string-like”. If the |
| printer’s <code>to-string</code> function returns a Guile string of some |
| kind, then <small>GDB</small> will call its internal language-specific |
| string-printing function to format the string. For the CLI this means |
| adding quotation marks, possibly escaping some characters, respecting |
| <code>set print elements</code>, and the like. |
| </p></dd> |
| </dl> |
| |
| </dd> |
| <dt>‘<samp>to-string</samp>’</dt> |
| <dd><p><var>to-string</var> is either a function of one parameter, the |
| <code><gdb:pretty-printer-worker></code> object, or <code>#f</code>. |
| </p> |
| <p>When printing from the CLI, if the <code>to-string</code> method exists, |
| then <small>GDB</small> will prepend its result to the values returned by |
| <code>children</code>. Exactly how this formatting is done is dependent on |
| the display hint, and may change as more hints are added. Also, |
| depending on the print settings (see <a href="Print-Settings.html#Print-Settings">Print Settings</a>), the CLI may |
| print just the result of <code>to-string</code> in a stack trace, omitting |
| the result of <code>children</code>. |
| </p> |
| <p>If this method returns a string, it is printed verbatim. |
| </p> |
| <p>Otherwise, if this method returns an instance of <code><gdb:value></code>, |
| then <small>GDB</small> prints this value. This may result in a call to |
| another pretty-printer. |
| </p> |
| <p>If instead the method returns a Guile value which is convertible to a |
| <code><gdb:value></code>, then <small>GDB</small> performs the conversion and prints |
| the resulting value. Again, this may result in a call to another |
| pretty-printer. Guile scalars (integers, floats, and booleans) and |
| strings are convertible to <code><gdb:value></code>; other types are not. |
| </p> |
| <p>Finally, if this method returns <code>#f</code> then no further operations |
| are peformed in this method and nothing is printed. |
| </p> |
| <p>If the result is not one of these types, an exception is raised. |
| </p> |
| <p><var>to-string</var> may also be <code>#f</code> in which case it is left to |
| <var>children</var> to print the value. |
| </p> |
| </dd> |
| <dt>‘<samp>children</samp>’</dt> |
| <dd><p><var>children</var> is either a function of one parameter, the |
| <code><gdb:pretty-printer-worker></code> object, or <code>#f</code>. |
| </p> |
| <p><small>GDB</small> will call this function on a pretty-printer to compute the |
| children of the pretty-printer’s value. |
| </p> |
| <p>This function must return a <gdb:iterator> object. |
| Each item returned by the iterator must be a tuple holding |
| two elements. The first element is the “name” of the child; the |
| second element is the child’s value. The value can be any Guile |
| object which is convertible to a <small>GDB</small> value. |
| </p> |
| <p>If <var>children</var> is <code>#f</code>, <small>GDB</small> will act |
| as though the value has no children. |
| </p></dd> |
| </dl> |
| </dd></dl> |
| |
| <p><small>GDB</small> provides a function which can be used to look up the |
| default pretty-printer for a <code><gdb:value></code>: |
| </p> |
| <dl> |
| <dt><a name="index-default_002dvisualizer"></a>Scheme Procedure: <strong>default-visualizer</strong> <em>value</em></dt> |
| <dd><p>This function takes a <code><gdb:value></code> object as an argument. If a |
| pretty-printer for this value exists, then it is returned. If no such |
| printer exists, then this returns <code>#f</code>. |
| </p></dd></dl> |
| |
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| Next: <a href="Selecting-Guile-Pretty_002dPrinters.html#Selecting-Guile-Pretty_002dPrinters" accesskey="n" rel="next">Selecting Guile Pretty-Printers</a>, Previous: <a href="Types-In-Guile.html#Types-In-Guile" accesskey="p" rel="prev">Types In Guile</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> |
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