Fundamentals of the Mathematica Programmnbg Language note set by Richard J. Gaylord

*To*: mathgroup at smc.vnet.net*Subject*: [mg49330] Fundamentals of the Mathematica Programmnbg Language note set by Richard J. Gaylord*From*: gaylord at uiuc.edu (richard j. gaylord)*Date*: Wed, 14 Jul 2004 07:29:37 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

my pdf and Mathematica note set are now available at: http://library.wolfram.com/infocenter/MathSource/5216/ to give you a flavor of what i am trying to emphasize in the note set, here is an excerpt. Mathematica Programming Fundamentals: Lecture Notes Richard Gaylord These notes form the basis of a series of lectures given by the author, in which the fundamental principles underlying Mathematica'sprogramming language are discussed and illustrated with carefully chosen examples. This is not a transcription ofthose lectures, but the note set was used to create a set of transparencies which he showed and spoke about during his lectures. These notes formed the basis for both a single 6 hour one-day lecture and a series of four 90 minute lectures, delivered to professionals and to students. Introduction In order to use Mathematica efficiently, you need to understand how the Mathematica programming language works. This tutorial (which has been extensively field-tested in university courses) is intended to provide you with the background that's needed to write your own code. Note: While this material can't replace the use of The Mathematica Book by Wolfram or Mathematica's online help (which give definitions of built-in functions and simple illustrations of their use), it can help to make you more comfortable with the Mathematica programming language which often seems obscure, even enigmatic, when first encountered by someone whoseprogramming experience is with one of the traditional procedural languages. In this note set, the following aspects of the Mathematica programming language are emphasized: the nature of expressions,how expressions are evaluated, how pattern-matching works, creating rewrite rules, and using higher-order functions. How expressions are evaluated Mathematica is a term rewriting system (TRS). Whenever an expression is entered, it is evaluated by term rewriting usingrewrite rules. These rules consist of two parts: a pattern on the left-hand side and a replacement text on the right-hand side. When the lhs of a rewrite rule is found to pattern-match part of the expression, that part is replaced by the rhs of the rule, after substituting values in the expression which match labelled blanks in the pattern into the rhs of the rule. Evaluation then proceeds by searching for further matching rules until no more are found. The evaluation process in Mathematica can be easily understood with the following analogy: Think of your experiences with using a handbook of mathematical formulas, such as the integral tables of Gradshteyn andRyzhik. In order to solve an integral, you consult the handbook which contains formulas consisting of a left-hand side (lhs) and a right-hand side (rhs), separated by an 'equals' sign. You look for an integration formula in the handbook whose left-hand side has the same form as your integral. Note: While no two formulas in the handbook have the identical lhs, there may be several whose lhs have the same form as your integral (eg., one lhs might have specific values in the integration limits of in the integrand, while another lhs has unspecified (dummy) variables for these quantities). When this happens, you use the formula whose lhs gives the closest fit to your integral. You then replace your integral with the right-hand side of the matching lhs and you substitute the specific values in your integral for the corresponding variable symbols in the rhs. Finally, you look through the handbook for formulas (eg., trigonometric identities or algebraic manipulation) that can be used to change the answer further. This depiction provides an excellent description of the Mathematica evaluation process. However, the application of the term rewriting process to a Mathematica expression requires a bit more discussion because a Mathematica expression consists of parts, a head and zero or more arguments which are themselves expressions. expr@expr1, expr2, ?, exprnD. It is therefore necessary to understand the order in which the various parts of an expression are evaluated by term rewriting. The implementation of the evaluation procedure is (with a few exceptions) straightforward: 1. If the expression is a number or a string, it isn't changed. 2. If the expression is a symbol, it is rewritten if there is an applicable rewrite rule in the global rule base; otherwise, it is unchanged. 3. If the expression is not a number, string or symbol, its parts are evaluated in a specific order: a. The head of the expression is evaluated. b. The arguments of the expression are evaluated from left to right in order. An exception to this occurs when the head is a symbol with a hold attribute (eg., HoldFirst, HoldRest, or HoldAll), so that some of its arguments are left in their unevaluated forms (unless they, in turn, have the head Evaluate). For example, the Set or SetDelayed function which we will discuss in a moment. 4. After the head and arguments of an expression are each completely evaluated, the expression consisting of the evaluated head and arguments is rewritten, after making any necessary changes to the arguments based on the Attributes (such asFlat, Listable, Orderless) of the head, if there is an applicable rewrite rule in the global rule base. 5. After carrying out the previous steps, the resulting expression is evaluated in the same way and then the result of that evaluation is evaluated, and so on until there are no more applicable rewrite rules. The details of the term-rewriting process in steps 2 and 4 are as follows: a. part of an expression is pattern-matched by the lhs of a rewrite rule b. the values which match labelled blanks in the pattern are substituted into the rhs of the rewrite rule and evaluated. c. the pattern-matched part of the expression is replaced with the evaluated result. note that while i am a strong proponent of the functional style of programming, the fundamental (in my opinion) nature of the Mathematica programming language is that it is a TERM REWRITING SYSTEM (aka an equational programming language). i would be interested in your general response to this note set, though i can't answer specific questions as that would eat into my retirment time.

**Re: Normal distribtion**

**definite integral**

**Re: User-defined or filled symbols for Points in ListPlots and Epilogs?**

**definite integral**