Chapter 12
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FRIENDLY PROGRAMMING
Software industry must be a miracle - a miracle that would
embody the vision of a quick and easy programming.
Tom Manuel
HYBRID programming languages ??DRAGON SI
Suppose you want to build a system on a hybrid visual
programming language DRAGON-SR. The problem can be solved, for
example, by means of three programs: the dragon-editor, the
dragon-converter and the C compiler. The user with the help of a
dragon-editor draws on the computer program in DRAGON-SR (Fig.
90, the right of the graph). Then a dragon-converter converts
the internal representation of graphic codes in C language
source code (Fig. 90, the middle of the graph), after which the
standard C compiler converts the source code into object code.
To better understand the benefits of language DRAGON-SR, we
perform mentally reverse conversion. As can be seen from Fig.
90, when converting the text of the program source code in
visual C program is divided into two parts. Assignment
statements, conditional expressions, and declarative description
of almost no changes are transferred to the visual program and
placed it inside the icons. The remaining tekstoelementy C
language (which may be called to remove or "parasitic") become
unnecessary, becoming a graphic lines and keywords are "yes" and
"no" (yes and no). Figure 90 shows that the list of parasitic
(deleted) elements C language is impressive: it includes all the
keywords in Examples 1-7 except thedefault, all curly, circular
and oblique brackets, colon, tags, comments in Examples 3-5, and
furthermore of semicolons in Examples 2, 3, 7 and 6 in part.
Thus, in order to build a language-SEA DRAGON, according to
certain rules need to connect the visual syntax of a dragon with
text syntax of the C language, removing the last of all the
elements whose functions are realized visual operators DRAGON. A
couple of the C language and the dragon-SI is equivalent in the
sense that it can be built converter performs both direct and
inverse transformation. This converter can convert the source
code in the language of DRAGON-SR (Fig. 90, the right of the
graph) to the equivalent C program (Fig. 90, the middle of the
graph), and vice versa.
Create any hybrid language (for example, a dragon-SI) can hardly
be considered original work since the latter is almost fully
preserves the concept, structure, data types, and other features
of the source language (SI). Correct to say that the
construction of a hybrid language (DRAGON SI) is technique in
which in a strictly defined number of cases of the source
language text notation is replaced by the visual. However, this
technique can significantly improve the ergonomic shape of the
source language.
Pidgin PROGRAMMING
DRAGON Modules
Referring to the above example in Fig. 91. The middle column
shows program in Modula-2, on the right - the equivalent program
in DRAGON modules. The left column is a list of keywords that
are used in the module-program and are "vital" for the language
module, but which do not need to program dragon.
From an ergonomic point of view, these and many other keywords
present in the text-based languages, there is nothing more than
a visual disturbance, attracting the attention of the reader and
distract his attention from the substantive aspect of the case.
Ergonomic advantage of the Dragon is that instead of keywords
used by the visual image that is perceived by the reader
unconsciously, on an intuitive level, while conscious attention
channel operates more efficiently - for the perception of the
most important, substantive aspects of the problem.
EXAMPLE ergonomic optimization
PROGRAMS
Fig. 91 (at the bottom, in the middle column) program is written
in Pascal. Acting similarly to the previous example, it can be
easily converted to a program in PASCAL dragon. To do this, draw
a visual statement "fork" and the icon "issue" put the record
K = 1 OR K = 2
Lower output icon "question" mark the word "yes" and join him
switch with two icons "option" and the right way (the answer is
"no") is connected to the icon "withdrawal" in which top write
WRITELN, bottom - ERROR. As a result, we obtain the Dragon
scheme, which is undoubtedly a completely correct solution of
the problem. (For clarity, we recommend the reader to perform
the construction on paper.)
But now change the conditions of the problem. Let's try to
create a program that would not only be equivalent to the Pascal
program in Fig. 91, and an ergonomically optimal for the
Russian-speaking reader. Seeking a program written in the
language of the Dragon 2 is shown in the same figure at the
bottom right.
Striking structural difference between the programs. Pascal
program contains two constructs: if-then-else and
case-of.Ergonomic optimization is that the dragon program uses
only one visual operator (the switch with three options), which
nevertheless "alone" performs the same function as the two text
operator Pascal. As a result, a complex condition K = 1 OR K = 2
and other excesses Pascal programs are eliminated, and the
dragon diagram is considerably simplified and becomes laconic,
clear and elegant.
Dialog programs
We continue the presentation of one of the possible approaches
to building a programming language DRAGON-2. Once again, we
recall that the reader will not find here the description of the
language. Our goal is much more modest: to show that the
formalization of the syntax of the language of the text DRAGON
is feasible, and to give a few examples to prove this point.
Consider interactive program in Fig. 92 and 93, having improved
teaching (teaching) properties. To do this, use an extensive set
of ergonomic tools. In particular, during filling of the icon
"comment" is used zoning text. Text comments to facilitate
understanding of spatially divided into two zones, which are,
firstly, have a clearly defined and easily discernible
boundaries, and secondly, a different color background (gray and
white). The gray area is placed the text that appears on the
computer screen in white - explaining to him. Delimitation
between the text of the explanatory comments easier to read and
improve their comprehensibility.
Ergonomic reception "zoning text" is useful not only in the
comments, but in other cases, such as input-output statements.
Operator "Message"
Operator "message" is used to display information on a computer
screen. It contains the icon "withdrawal", on the top floor
which put the keyword "Message" at the lower - output
information. In describing the final text of the zoning applies:
in the gray zone write variable names or expressions (values
??should be displayed on the screen), a white zone - permanent
information (which is displayed unchanged). Newline is a black
circle. For example, in Fig. 92 using the "Message" appears on
the screen, the phrase "sum of the numbers is" and the
expression m + n.
Operator "Request"
Operator "Request" shall enter into the computer the values ??of
variables, display fixed information, variable names and values
??entered. In the upper part of the icon "input" write the
keyword "Query" at the bottom - the input and output
information. There is also present zoning of the text: in the
gray area indicate the names of the variables to be entered into
the computer, in white - put a constant information.
Suppose you want to enter the values ??m = 23 and n = 45 (Fig.
92). This is done, for example, as the cursor is fed into the
zone m, type in the number 23 and press the "carriage return."
Wherein m area on the screen disappears and instead the number
of turns 23. The value of n is introduced analogously. Thus, the
operator "Query" prompts the user variables, stores them in
memory, and simultaneously displays on the screen along with the
constant information (if the latter is available on the ground
floor of the operator "Query" in the white zone).
Data Description
For a description of the data is the icon of "shelf". Upstairs
write the keyword "data" at the bottom - a description of the
data. For example, in Fig. 92 in the icon "regiment" indicated
that the variables m and n are of the type "a."
You can offer another way: data description endure beyond the
dragon-circuit and placed in a separate table.
IDs
Here are the rules for writing identifiers.
* The length of the identifier 1 ... 32 characters.
* Permission is granted to use any of Russian and Latin
letters, numbers, periods, and may have special characters.
* The first character must be a letter (not a digit and not
the point).
* Inside the identifier may not use spaces.
* Words must be separated by dots, to facilitate reading.
* Do not use the contraction of the words, if the length of
the ID is less than 32 characters.
* If the length of the identifier more than 32 characters, it
is necessary to replace certain words or abbreviations to
reduce the number of words.
* We must strive to come up with intelligible identifiers make
it easy to understand the meaning of the concept, so that
the reader quickly understand the essence.
Examples of valid ID
Nomer.vagona.skorogo.poezda
Nomer.vagona.passazhir.poezda
Tsena.bileta.poezdom.do.Magadana
Tsena.bileta.samolet.do.Magadana
Examples of invalid identifiers
Nomer.vagona.passazhirskogo.poezda (Here 33 symbols,and can be
no more than 32)
Chislo.vagonov freight train (Spaces are used)
(There are two mistakes:First
3 y.zapusk.avariynogo.nasosa symbol - the figure; In
addition, there is a hyphen)
An example of reducing the length of the complex concept
Suppose you want to create an identifier for the following
notion: "The radius vector of the center of the Earth at the
center of the runway in the landing coordinates." Verbal
description of the concept contains 92 characters. The aim is to
reduce the 92-character description of up to 32-character,
retaining as much as possible a clear sense of the concept.
Reducing spend on the following schedule:
* "The radius vector of the center of the Earth" substitute
"Radius.zemli."
* Instead of "In the center of the runway," write "na.polose."
* "The landing coordinate system" is replaced by the CPM, as
this reduction is commonly used in the collective
development of the system.
As a result, we obtain a 26-character identifier
Radius.zemli.na.polose.PSK
which retains nearly all the key words of the original concepts
and provides a relatively high comprehensibility.
Record rules of arithmetic expressionsassignment statements
We must distinguish two cases. If the expression is simple, it
is recommended to use a 32-character identifiers, and "vertical"
record mathematical formulas, as shown in Fig. 94 and 95.
However, when it comes to complex mathematical calculations, the
method described is not suitable as a "vertical" formula with a
32-character identifiers do not allow the reader to see the
mathematical structure calculations, diverting his attention to
reading long identifiers that, paradoxically, turn out useful
tips into its opposite and begin to play a negative role of
visual interference. Thus, there is an ergonomic impasse: short
identifiers do not allow you to quickly understand the meaning
of concepts and long - obscure the structure of complex
formulas.
As one of the possible approaches to the outbreak of this
Gordian knot can be offered a three-point plan.
* For each mathematical concept provides two identifiers: a
long (32-character) and short (alias).
* In arithmetic expressions are used only aliases, which makes
the structure of formulas transparent.
* ? In the beginning of the program provides an icon
"comment", which houses a table of correspondences between
aliases and long identifiers. This table serves as a crib,
which is in the same field of vision with assignment
operators and allows you to quickly recall, which means that
one or another alias.
Array processing
Fig. 94 and 95 are examples of programs that have operations on
arrays.
Data description located on the ground floor of the icon
"regiment."
Record ARRAY VESCH Ves.krolika [2]100
It means that the specified one-dimensional array called
"Ves.krolika" containing 100 elements, each of which is a real
number.
The main element of both programs is the cycle for. Consider the
rules of registration cycle. In the icon "start cycles for" in
the top line of writing the word "cycle" and after a space
one-character alias, indicating the loop variable (the letter k
in Fig. 94, 95). The bottom line indicates the range of change,
for example,
from k = 1 to 100
But what stands for the letter k? What is the physical meaning
of the loop variable in the application program? The authors of
many programs forget (or do not consider it necessary) to answer
this question, with the result that the program often turns into
a puzzle. To avoid this, in the middle line should write a
formal comment, for example,
k = Nomer.krolichey.kletki
= identically equal sign shows that after followed by the name,
comment, t. E. Comment that is written by the rules record
identifiers.
Ergonomic "fat" formal comment involves two advantages. First,
it eliminates the traditional "forgetfulness" of programmers and
humanly explain to the reader the meaning of abstract ID: say, k
- is the number of rabbit cages. Second, importantly, the
explanation is placed on the drawing exactly where needed (in
the icon "start cycle for"), on the principle of "expensive egg
to the day of Christ." This means that the reader gets an
instant response - at the very moment when he first saw the
alias k and glimmer in his mind a question: What is k?
The icon of the "end of cycle for the" record
End cycle (loop variable)
The meaning of the operators that organize array processing is
clear from Fig. 94 and 95 and requires no explanation.
ABSTRACT DRAGON diagram
In this section we will look at the transformation of the visual
language program DRAGON-2 in the text program in BASIC.This
transformation is useful in two ways: it will allow deeper
visualization to understand the essence and learn important
concept abstract dragon scheme.
As an example, take a school program called "Igra.ugadayka" and
write it in the language of the Dragon 2 (Fig. 96). Then,
completely eliminate it from the text and get the drawing-mole
rat, which is called "abstract dragon diagram" (Fig. 97). This
scheme is an invariant of the program, which can be converted in
two steps in the program in any programming language.
We choose as the target language BASIC and get down to business.
The first step is to fill the empty icon abstract schema text in
the language BASIC. The result is the equivalent program in
BASIC-DRAGON (Fig. 98). In the second step we pass to normal
BASIC program (we deliberately chose the old-fashioned version
of BASIC to demonstrate the use for a variety of goto statements
when describing equivalent dragon program) - see. Fig. 99.
Philosophy of language DRAGON
Any imperative language (C, Pascal, ADA, modules, BASIC, and so
on. D.) Can be divided into three parts, three relatively
independent language: routing, command and declarative.
Trip language - a set of control statements. Command language
contains all the non-control statements, such as the assignment
operator, the rules for writing arithmetic and logical
expressions, identifiers, keywords, and so on. D.Declarative
language used to describe data, and other classes.
Let us illustrate this with an example. Abstract dragon diagram
shown in Fig. 97, there is some "words" Shuttle language.To make
it meaningful, icons should be placed within the text. This text
is written in the command language. However, the description of
data classes and sometimes it is advisable to make the scope of
the dragon-circuit and put them somewhere else, such as a single
record or table.
Hence the principle of differentiation of three sublanguages.
Trip language - the language of "pictures" (abstract dragon
schemes in which the text is completely absent). Command
language used to write text inside dragon scheme declaratory -
for those records that can be taken outside its borders.
Constructing another language dragon family, you can select a
team and declarative sublanguages ??in any way (by borrowing
from other languages, or inventing anew). This provides a wealth
of features dragons and flexible configuration for various
applications. Thus, the dragon family has only one hard link -
trip language that is none other than the visual components
DRAGON (visual syntax and semantics).
Trip language - a visual standard dragon family, dragon supports
visual editor (see. Ch. 14), which is small and easy to
remember. He is a constant hallmark of the Dragon, its
standardized visual image (Fig. 97).
CLASSIFICATION OF KNOWLEDGE
Every program has a certain amount of knowledge, which can be
separated into an imperative and declarative part.The above
considerations make it possible to clarify this thesis. A new
approach to the problem is presented in Fig. And 100 is as
follows:
* ? To analyze the knowledge contained in the source code of a
computer program written in an imperative language, it is
advisable to use two classifications: basic and alternative.
/ Li>
* Basic classification is that all the knowledge contained in
the initial program, split into declarative and imperative.
* In turn, the imperative of knowledge are divided into
control and command.
* As a criterion for the alternative classification proposed
question: what tools are best used for knowledge
representation - graphics or text?
* The answer is as follows. To present knowledge of Governors
is better to use the schedule (Block language) for command
and declarative knowledge - text.
* Thus, in the alternative classification of knowledge is
divided into visual (control), and text (command and
declarative).
Finally add: the use of the text for submission to the complex
control of knowledge seems as absurd as an attempt to describe a
map in words. The fact that the text is still used for this
purpose, can be explained only one: the programming is much
younger than geography!
CONCLUSIONS
1. If we now have a formal visual syntax, for the construction
of a visual programming language is sufficient to construct
a formal text syntax. We are convinced that this problem is
quite solvable, and in several ways. The end result, a
family of programming languages ??as the original (the
dragon-2), and hybrid (DRAGON-SR-DRAGON modules DRAGON
Pascal, BASIC and dragon t. H.).
2. It can be argued that the comprehensibility of visual
languages ??is significantly higher than the
comprehensibility of their text counterparts. Therefore, in
all cases where the comprehensibility is regarded as the
main criterion for the quality of programs (and there are a
lot of cases), visual languages ??are out of competition. It
is appropriate caveat: the very term "visually" does not
guarantee anything. Business success is achieved through a
thorough and rigorous application of the science of human
factors (ergonomics). To be more precise, it is a synthesis
of methods of computer science and ergonomics, the formation
of a new interdisciplinary direction - infoergonomiki, the
restructuring of the building of modern programming
ergonomic basis.
3. The creation of any programming language, the next
generation must begin with an analysis of ergonomic
requirements and end with evaluation of the ergonomic
features of the language. One of the main obstacles to the
implementation of this plan is the inertia of thinking of
many experts, an underestimation of the importance of
ergonomic methods. To change the stereotypes of thinking,
you need to make major changes in the program and methods of
teaching of computer science in schools and universities.
References
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