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| author | Rico Tzschichholz <ricotz@ubuntu.com> | 2020-03-23 14:57:51 +0100 |
|---|---|---|
| committer | Rico Tzschichholz <ricotz@ubuntu.com> | 2020-03-23 17:17:32 +0100 |
| commit | cca368f278707b9cf637082a65efca1742a33aa6 (patch) | |
| tree | c20f9455bc450ea16a56caf913c51114d36f3739 /doc | |
| parent | 33269238ff35db06b8e36b848c9ad8b983ad7437 (diff) | |
| download | vala-cca368f278707b9cf637082a65efca1742a33aa6.tar.gz | |
manual: Update from wiki.gnome.org
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/manual/manual.xml | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/doc/manual/manual.xml b/doc/manual/manual.xml index d551a428b..3eeb9d0cc 100644 --- a/doc/manual/manual.xml +++ b/doc/manual/manual.xml @@ -1085,14 +1085,25 @@ <section> <title>Contract programming</title> -<para>TODO: requires, ensures. </para> -<para>requires ( ... ) Denotes things that must be true to start execution. </para> -<para>ensures ( ... ) Denotes things that must be true to end execution. </para> -</section> - -<section> -<title>Examples</title> -<para>TODO: write examples. </para> +<para>Vala supports basic <ulink url="http://en.wikipedia.org/wiki/Contract_programming">contract programming</ulink> features. A method may have preconditions (<code>requires</code>) and postconditions (<code>ensures</code>) that must be fulfilled at the beginning or the end of a method respectively: </para><programlisting format="linespecific" language="highlight" linenumbering="numbered" startinglinenumber="1"><token><![CDATA[double]]></token><![CDATA[ ]]><methodname><![CDATA[method_name]]></methodname><![CDATA[ (]]><token><![CDATA[int]]></token><![CDATA[ ]]><methodname><![CDATA[x]]></methodname><![CDATA[, ]]><token><![CDATA[double]]></token><![CDATA[ ]]><methodname><![CDATA[d]]></methodname><![CDATA[)]]> +<![CDATA[ ]]><token><![CDATA[requires]]></token><![CDATA[ (]]><methodname><![CDATA[x]]></methodname><![CDATA[ > 0 && ]]><methodname><![CDATA[x]]></methodname><![CDATA[ < 10)]]> +<![CDATA[ ]]><token><![CDATA[requires]]></token><![CDATA[ (]]><methodname><![CDATA[d]]></methodname><![CDATA[ >= 0.0 && ]]><methodname><![CDATA[d]]></methodname><![CDATA[ <= 1.0)]]> +<![CDATA[ ]]><token><![CDATA[ensures]]></token><![CDATA[ (]]><methodname><![CDATA[result]]></methodname><![CDATA[ >= 0.0 && ]]><methodname><![CDATA[result]]></methodname><![CDATA[ <= 10.0) {]]> +<![CDATA[ ]]><token><![CDATA[return]]></token><![CDATA[ ]]><methodname><![CDATA[d]]></methodname><![CDATA[ * ]]><methodname><![CDATA[x]]></methodname><![CDATA[;]]> +<![CDATA[}]]> +</programlisting> +<para><code>result</code> is a special variable representing the return value. </para> +<para>For example, if you call <code>method_name</code> with arguments <code>5</code> and <code>3.0</code>, it will output a CRITICAL message and return 0. </para><programlisting format="linespecific" language="highlight" linenumbering="numbered" startinglinenumber="1"><token><![CDATA[void]]></token><![CDATA[ ]]><methodname><![CDATA[main]]></methodname><![CDATA[ () {]]> +<![CDATA[ ]]><methodname><![CDATA[stdout]]></methodname><![CDATA[.]]><methodname><![CDATA[printf]]></methodname><![CDATA[ (]]><phrase><![CDATA["]]></phrase><phrase><![CDATA[%i]]></phrase><![CDATA[ +]]><phrase><![CDATA["]]></phrase><![CDATA[, ]]><methodname><![CDATA[method_name]]></methodname><![CDATA[ (5, 3.0));]]> +<![CDATA[}]]> +</programlisting> +<para>Output: </para><screen><![CDATA[CRITICAL **: 03:29:00.588: method_name: assertion 'd >= 0.0 && d <= 1.0' failed +0]]></screen> +<para>Vala allows you to manage the safety of issued messages at 6 levels: ERROR, CRITICAL, INFO, DEBUG, WARNING, MESSAGE. For example, the following code will cause a runtime error. </para><programlisting format="linespecific" language="highlight" linenumbering="numbered" startinglinenumber="1"><methodname><![CDATA[Log]]></methodname><![CDATA[.]]><methodname><![CDATA[set_always_fatal]]></methodname><![CDATA[ (]]><methodname><![CDATA[LogLevelFlags]]></methodname><![CDATA[.]]><methodname><![CDATA[LEVEL_CRITICAL]]></methodname><![CDATA[ | ]]><methodname><![CDATA[LogLevelFlags]]></methodname><![CDATA[.]]><methodname><![CDATA[LEVEL_WARNING]]></methodname><![CDATA[);]]> +<methodname><![CDATA[stdout]]></methodname><![CDATA[.]]><methodname><![CDATA[printf]]></methodname><![CDATA[ (]]><phrase><![CDATA["]]></phrase><phrase><![CDATA[%i]]></phrase><![CDATA[ +]]><phrase><![CDATA["]]></phrase><![CDATA[, ]]><methodname><![CDATA[method_name]]></methodname><![CDATA[ (5, 3.0));]]> +</programlisting> </section> </section> <para>Back to <ulink url="https://wiki.gnome.org/Projects/Vala/Manual/Export/Projects/Vala/Manual#">Vala Reference Manual</ulink> </para> |