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 #### Options
 
+* [Code metrics](options_code_metrics)
 * [Compiler paths](options_compilers_paths.html)
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+### Code metrics
+
+The quality of the D code is verifiable using code metrics.
+In general several metrics exist:
+
+* simple Source Line of Code (SLOC), white lines and comment counter.
+* [Halstead complexity](https://en.wikipedia.org/wiki/Halstead_complexity_measures): quality indicator based on the count of operators and operands.
+* [Cyclomatic complexity](https://en.wikipedia.org/wiki/Cyclomatic_complexity): quality indicator based on the program execution flow.
+
+Coedit implements the Halstead metric. The other may be added in a further version.
+
+#### Halstead complexity
+
+The metric uses the count and the sum of the functions operands and operators to compute several indexes. Even it's clearly related to the SLOC it's more accurate. For example:
+
+```D
+void foo() 
+{
+    int a = 1, b;
+    a = a + a;
+}
+```
+
+Is seen as less complex than
+
+```D
+void foo() 
+{
+    int a = 1, b;
+    a = a + b++;
+}
+```
+
+Even if the SLOC count is the same.
+
+The verification is launched from the _File_ menu, _View Halstead metrics_.
+Each free function and member function of the module that has the focus is measured.
+When thresholds are crossed warnings are emitted. There is 3 possible warnings:
+
+* the maximal estimated number of bugs per function is reached, by default 0.5.
+* the maximal estimated number of bugs per module is reached, by default 2.
+* the maximal volume of a function is reached, by default 2000.
+
+Warnings are informative. They should simply be interpreted as an indicator that a function must be more tested or refactorized.
+
+It's important to note that the limits of the measure:
+
+* even with D embedded unit test, the measure is not able to detect that a complex function is well tested.
+* the evolution of the quality over the time is not followed-up.
+* results are only relevant with the _imperative_ and _object oriented_ programming paradigm. Template Meta Programming will give wrong results. UFCS chain are not detected as consecutive calls.
+
+Default values can be modified in the option editor:
+
+![](img/code_metrics.png)
+
+The maximal volume of a module is not verified, simply because it's possible to have huge modules with many high quality small functions.
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diff --git a/docs/options_compilers_paths.md b/docs/options_compilers_paths.md
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@@ -8,17 +8,17 @@ These settings are important and should be verified after the installation.
 
 Up to five D compilers can be defined.
 
-* DMD: should be set to the stable DMD version. The paths are normally detected when _Coedit_ is launched for hte first time.
-* GDC: should be set to the stable GDC version. The _runtime_ and _Phobos_ sources stand in the same folder so the third field can be left empty.
-* LDC: should be set to the stable GDC version. The _runtime_ and _Phobos_ sources stand in the same folder so the third field can be left empty.
-* User1: can be set to any compiler, for the example the development version of DMD.
-* User2: same as _User1_.
+* __DMD__: should be set to the stable DMD version. The paths are normally detected when _Coedit_ is launched for hte first time.
+* __GDC__: should be set to the stable GDC version. The _runtime_ and _Phobos_ sources stand in the same folder so the third field can be left empty.
+* __LDC__: should be set to the stable LDC version. The _runtime_ and _Phobos_ sources stand in the same folder so the third field can be left empty.
+* __User1__: can be set to any compiler, for the example the development version of DMD.
+* __User2__: a second user-defined compiler.
 
 The combo box at the top is used to select which are the paths passed to the completion daemon. 
 When the completion daemon is launched by _Coedit_ the change is applied directly after the validation, otherwise it has to be restarted manually.
 
-In other categories of the options one of these compilers can be selected.
+In other options categories one of these compilers can be selected.
 
-* Category _Application_, __nativeProjectCompiler_: defines the compiler used to compile a project that has the native format.
+* Category _Application_, _nativeProjectCompiler_: defines the compiler used to compile a project that has the native format.
 * Category _Runnable modules_, _compiler_: defines the compiler used to compile a _runnable module_ or a DUB script.
 * Category _DUB build_, _compiler_: defines the compiler used to compile a project that has the DUB format.
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