Update doc/specs/stdlib_constants.

Author: MilanSkocic

doc/specs/stdlib_constants.md

@@ -9,10 +9,33 @@ title: constants
 
 The [[stdlib_constants]] module provides mathematical constants and the most common physical constants.
 
-The [[stdlib_codata]] module defines all codata constants as derived type [[codata_constant_type]].
-The latest codata constants were released in 2018 by the [NIST](http://physics.nist.gov/constants.)
+
+## Codata
+
+The [[stdlib_codata(module)]] module defines all codata (physical) constants as derived 
+type. The latest codata constants 
+were released in 2018 by the [NIST](http://physics.nist.gov/constants)
+All values for the codata constants are provided as double precision reals. 
 The names are quite long and can be aliased with shorter names.
 
+The derived type [[stdlib_codata_type(module):codata_constant_type(type)]] defines:
+procedures.
+
+* 4 members:
+
+    * `name` (string)
+    * `value` (double precision real)
+    * `uncertainty` (double precision real)
+    * `unit` (string)
+
+* 2 type-bound procedures:
+
+    * `print` for print the values of the constant members.
+    * `to_real` for converting the value or the uncertainty to the desired precision.
+
+A module level interface [[stdlib_codata_type(module):to_real(interface)]] is available for converting the constant value
+or uncertainty.
+
 
 ## Example
 

src/stdlib_codata_type.fypp

@@ -2,6 +2,7 @@
 #:set KINDS = REAL_KINDS
 module stdlib_codata_type
     !! Codata constant type
+    !! ([Specification](../page/specs/stdlib_constants.html))
     use stdlib_kinds, only: #{for k in KINDS[:-1]}#${k}$, #{endfor}#${KINDS[-1]}$
     use stdlib_io, only: FMT_REAL_DP
     use stdlib_optval, only: optval 
@@ -11,7 +12,7 @@ module stdlib_codata_type
         !! version: experimental
         !!
         !! Derived type for representing a Codata constant.
-        !! [Specification](TOBECOMPLETED)
+        !! ([Specification](../page/specs/stdlib_constants.html))
         character(len=64) :: name
         real(dp) :: value
         real(dp) :: uncertainty
@@ -46,7 +47,7 @@ elemental pure real(${k}$) function to_real_${k}$(self, mold, uncertainty) resul
     !! version: experimental
     !!
     !! Get the constant value or uncertainty for the kind ${k}$
-    !! [Specification](TO_BE_COMPLETED)
+    !! ([Specification](../page/specs/stdlib_constants.html))
 
     class(codata_constant_type), intent(in) :: self !! Codata constant
     real(${k}$), intent(in) :: mold !! dummy argument to disambiguate at compile time the generic interface

src/stdlib_constants.fypp

@@ -2,6 +2,7 @@
 #:set KINDS = REAL_KINDS
 module stdlib_constants
     !! Constants
+    !! ([Specification](../page/specs/stdlib_constants.html))
     use stdlib_kinds, only: #{for k in KINDS[:-1]}#${k}$, #{endfor}#${KINDS[-1]}$
     use stdlib_codata, only: SPEED_OF_LIGHT_IN_VACUUM, &
                              VACUUM_ELECTRIC_PERMITTIVITY, &