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authorRichard Carlsson <[email protected]>2014-05-06 10:34:07 +0200
committerHans Bolinder <[email protected]>2015-03-10 10:21:41 +0100
commit8e7441c27485bd416abdb0253c9c92620d671065 (patch)
tree6d722b99dd0f001346450b14903e7e6f79379ecc /lib/stdlib/doc/src
parent4037296294670e7a9bb2a3c1cdbd0236cbc15807 (diff)
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Make the scanned form of the io_lib format strings available for processing
This adds three new functions to io_lib - scan_format/2, unscan_format/1, and build_text/1 - which expose the parsed form of the format control sequences to make it possible to easily modify or filter the input to io_lib:format/2. This can e.g. be used in order to replace unbounded-size control sequences like ~w or ~p with corresponding depth-limited ~W and ~P before doing the actual formatting.
Diffstat (limited to 'lib/stdlib/doc/src')
-rw-r--r--lib/stdlib/doc/src/io.xml3
-rw-r--r--lib/stdlib/doc/src/io_lib.xml70
2 files changed, 71 insertions, 2 deletions
diff --git a/lib/stdlib/doc/src/io.xml b/lib/stdlib/doc/src/io.xml
index a28180b42a..8ebfdb2e7f 100644
--- a/lib/stdlib/doc/src/io.xml
+++ b/lib/stdlib/doc/src/io.xml
@@ -505,7 +505,8 @@ ok
<p>Writes the data with standard syntax in the same way as
<c>~w</c>, but breaks terms whose printed representation
is longer than one line into many lines and indents each
- line sensibly. It also tries to detect lists of
+ line sensibly. Left justification is not supported.
+ It also tries to detect lists of
printable characters and to output these as strings. The
Unicode translation modifier is used for determining
what characters are printable. For example:</p>
diff --git a/lib/stdlib/doc/src/io_lib.xml b/lib/stdlib/doc/src/io_lib.xml
index 3312b08064..2117d66381 100644
--- a/lib/stdlib/doc/src/io_lib.xml
+++ b/lib/stdlib/doc/src/io_lib.xml
@@ -4,7 +4,7 @@
<erlref>
<header>
<copyright>
- <year>1996</year><year>2013</year>
+ <year>1996</year><year>2014</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
@@ -59,6 +59,35 @@
<datatype>
<name name="latin1_string"/>
</datatype>
+ <datatype>
+ <name name="format_spec"/>
+ <desc><p>Description:</p>
+ <list type="bulleted">
+ <item><p><c>control_char</c> is the type of control
+ sequence: <c>$P</c>, <c>$w</c>, and so on;</p>
+ </item>
+ <item><p><c>args</c> is a list of the arguments used by the
+ control sequence, or an empty list if the control sequence
+ does not take any arguments;</p>
+ </item>
+ <item><p><c>width</c> is the field width;</p>
+ </item>
+ <item><p><c>adjust</c> is the adjustment;</p>
+ </item>
+ <item><p><c>precision</c> is the precision of the printed
+ argument;</p>
+ </item>
+ <item><p><c>pad_char</c> is the padding character;</p>
+ </item>
+ <item><p><c>encoding</c> is set to <c>true</c> if the translation
+ modifier <c>t</c> is present;</p>
+ </item>
+ <item><p><c>strings</c> is set to <c>false</c> if the modifier
+ <c>l</c> is present.</p>
+ </item>
+ </list>
+ </desc>
+ </datatype>
</datatypes>
<funcs>
<func>
@@ -260,6 +289,45 @@
</desc>
</func>
<func>
+ <name name="scan_format" arity="2"/>
+ <fsummary>Parse all control sequences in the format string</fsummary>
+ <desc>
+ <p>Returns a list corresponding to the given format string,
+ where control sequences have been replaced with
+ corresponding tuples. This list can be passed to <seealso
+ marker="#build_text/1">io_lib:build_text/1</seealso> to have
+ the same effect as <c>io_lib:format(Format, Args)</c>, or to
+ <seealso
+ marker="#unscan_format/1">io_lib:unscan_format/1</seealso>
+ in order to get the corresponding pair of <c>Format</c> and
+ <c>Args</c> (with every <c>*</c> and corresponding argument
+ expanded to numeric values).</p>
+ <p>A typical use of this function is to replace unbounded-size
+ control sequences like <c>~w</c> and <c>~p</c> with the
+ depth-limited variants <c>~W</c> and <c>~P</c> before
+ formatting to text, e.g. in a logger.</p>
+ </desc>
+ </func>
+ <func>
+ <name name="unscan_format" arity="1"/>
+ <fsummary>Revert a pre-parsed format list to a plain character list
+ and a list of arguments</fsummary>
+ <desc>
+ <p>See <seealso
+ marker="#scan_format/2">io_lib:scan_format/2</seealso> for
+ details.</p>
+ </desc>
+ </func>
+ <func>
+ <name name="build_text" arity="1"/>
+ <fsummary>Build the output text for a pre-parsed format list</fsummary>
+ <desc>
+ <p>See <seealso
+ marker="#scan_format/2">io_lib:scan_format/2</seealso> for
+ details.</p>
+ </desc>
+ </func>
+ <func>
<name name="indentation" arity="2"/>
<fsummary>Indentation after printing string</fsummary>
<desc>