Fill out descriptions on section names

mathics/builtin/combinatorial.py

@@ -1,6 +1,10 @@
 # -*- coding: utf-8 -*-
 """
-Combinatorial Functions
+Combinatorics
+
+Combinatorics is an area of mathematics primarily concerned with counting, both as a means and an end in obtaining results, and certain properties of finite structures.
+
+It is closely related to many other areas of mathematics and has many applications ranging from logic to statistical physics, from evolutionary biology to computer science, etc.
 """
 
 

mathics/builtin/control.py

@@ -2,7 +2,13 @@
 # -*- coding: utf-8 -*-
 
 """
-Control Statements
+Procedural Programming
+
+Procedural programming is a programming paradigm, derived from imperative programming, based on the concept of the procedure call.
+
+Procedures (a type of routine or subroutine) simply contain a series of computational steps to be carried out. Any given procedure might be called at any point during a program's execution, including by other procedures or itself.
+
+Procedural functions and are integrated into Mathics symbolic programming environment.
 """
 
 

mathics/builtin/datentime.py

@@ -2,6 +2,10 @@
 
 """
 Date and Time
+
+Dates and times are represented symbolically; computations can be performed on them.
+
+Date object can also input and output dates and times in a wide range of formats, as well as handle calendars.
 """
 
 from datetime import datetime, timedelta

mathics/builtin/functional.py

@@ -1,7 +1,10 @@
 # -*- coding: utf-8 -*-
 
-"""
-Functional Programming
+"""Functional Programming
+
+Functional programming is a programming paradigm where programs are constructed by applying and composing functions.
+
+It is made richer by expressions like $f$[$x$] being treating as symbolic data.
 """
 
 from itertools import chain

mathics/builtin/optimization.py

@@ -1,4 +1,12 @@
 # -*- coding: utf-8 -*-
+"""Mathematical Optimization
+
+Mathematical optimization is the selection of a best element, with regard to some criterion, from some set of available alternatives.
+
+Optimization problems of sorts arise in all quantitative disciplines from computer science and engineering to operations research and economics, and the development of solution methods has been of interest in mathematics for centuries.
+
+We intend to provide local and global optimization techniques, both numeric and symbolic.
+"""
 
 from mathics.version import __version__  # noqa used in loading to check consistency.
 from mathics.builtin.base import Builtin

mathics/builtin/tensors.py

@@ -2,6 +2,10 @@
 
 """
 Tensors
+
+In mathematics, a tensor is an algebraic object that describes a (multilinear) relationship between sets of algebraic objects related to a vector space. Objects that tensors may map between include vectors and scalars, and even other tensors.
+
+There are many types of tensors, including scalars and vectors (which are the simplest tensors), dual vectors, multilinear maps between vector spaces, and even some operations such as the dot product. Tensors are defined independent of any basis, although they are often referred to by their components in a basis related to a particular coordinate system.
 """
 
 from mathics.version import __version__  # noqa used in loading to check consistency.