Turbo Prolog

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9 Tutorial VII: Files and Strings Turbo Prolog is extremely rich in file and string-handling facilities. Rather than giving a long list of standard predicates that might seem daunting at first sight, this chapter gives the standard predicates in related families. Each family of predicates is followed by some example programs which illustrate the use of predicates in that family. A complete classified (and alphabetized) list of standard predicates can be found in Chapter 12. The chapter concludes with a description of the very important standard predicate {indoll (which is used to collect the values of a variable that satisfy a given clause into a list) and of the random number generator random. THE TURBO PROLOG FILE SYSTEM In this section, we'll take a look at the Turbo Prolog file system and the standard read and write predicates that are relevant to files. The standard predicates for reading and writing are elegant and efficient. With just a single command, output can, for instance, be routed to a file instead of being displayed on the screen. In fact, Turbo Prolog makes use of a currenueod_device, from which input is read, and a currenLwrite_device, to which output is sent. Normally, the keyboard is the current read device and the screen is the current write device, but you can specify other devices. For instance, input could be read from a file that is stored externally (on disk perhaps), and output could be sent to a printer. Moreover, it is possible to reassign the current input and output devices while a program is running. Regardless of what read and write devices are used, reading and writing are handled identically within a Turbo Prolog program. 99
To access a file, it must first be opened. A file can be opened in four ways: • For reading • For writing • For appending to the file • For modification A file opened for any activity other than reading must be closed when that activity is finished or the changes to the file will be lost. Several files may be open simultaneously, and input and output can be quickly redirected between open files. In contrast, it takes longer to open and close a file than to redirect data between files. When a file is opened, Turbo Prolog connects a symbolic name to the actual name of the file used by DOS. This symbolic name is used by Turbo Prolog when input and output are redirected. Symbolic file names must start with a lowercase letter and must be declared in the file domain declaration: file = fileL ; source ; auxiliary Only one file domain is allowed in any program, and the four symbols printer screen keyboard comL are automatically defined in advance in the file domain and must not appear in the file declaration. printer refers to the parallel printer port and com I refers to the serial communication port. Following are the standard predicates for opening and closing files. openread{SyrnbolicFileNarne,DosFileNarne) The file DosFileName is opened for reading. The file is then referred to by the symbolic name SymbolicFileName. If the file is not found, the predicate fails. If DosFileName is illegal, an error message is displayed. openwrite{SyrnbolicFileNarne,DosFileNarne) The file DosFileName is opened for writing. If the file already exists, it is deleted. Otherwise, the file is created and an entry made in the appropriate DOS directory. openappend{SyrnbolicFileNarne,DosFileNarne) The file DosFileName is opened for appending. If the file is not found, an error message is displayed and execution halted. openrnodify{SyrnbolicFileNarne,DosFileNarne) The file DosFileName is opened for both reading and writing. openmodify can be used in conjunction with the (ilepos standard predicate (see page 102) to update a random access file. ]00 Turbo Prolog Owner's Handbook
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Turbo Prolog Owner's Handbook Copyr
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Chapter 4 Tutorial II: A Closer Loo
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Dynamic Databases in Turbo Prolog D
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fail field_attr field_str filepos f
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I 1-2 Sample Diagnostic Display ...
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The tutorials cover all aspects of
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Prolog is a full-fledged compiler w
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Turbo Prolog has a built-in pattern
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In addition to the version of Turbo
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Saving a Window Layout Select Save
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The clauses section contains a coll
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Objects and Relations In Turbo Prol
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Since Person I and Person2 are both
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mother(marilyn,beverly). mother(ala
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so that a goal of the form similar_
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32 Turbo Prolog Owner's Handbook
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1* Program b *1 domains person, hob
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Program 7 is a complete Turbo Prolo
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To declare a domain for lists of in
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Page 66 and 67: The clause Turbo Prolog chooses to
Page 68 and 69: Use of Fail Turbo Prolog contains a
Page 72 and 73: Exercise Suppose an average taxpaye
Page 74 and 75: 6 Tutorial IV: Arithmetic, Simple I
Page 78 and 79: eply(_,_,D) :- D < 0, write("No sol
Page 80: and A= -0.756802 tes t2 ( L; , B) .
Page 85: DEBUGGING AND TRACING Before a prog
Page 88 and 89: 7 Tutorial V: Seeing Through Turbo
Page 90 and 91: makewindow( ... ) shiftwindow( ...
Page 92 and 93: You can change the attribute of the
Page 97: A WORD GUESSING GAME USING WINDOWS
Page 100 and 101: goal 1* Program 32 *1 makewindow(1,
Page 102: 8 Tutorial VI: Graphics and Sound A
Page 106: 1 Program 37 1/ predicates inspiral
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Page 119 and 120: Program 50 uses random to select th
Page 121 and 122: 110 1* Program 51*1 predicates anim
Page 123 and 124: The other rule for positive will as
Page 125 and 126: Try the program with the goal route
Page 127 and 128: track as soon as one solution has b
Page 129 and 130: * Program 55 */ domains loc = right
Page 132: string word ("" , [ 1 ) : -! . stri
Page 136 and 137: Program 59 makes use of the readkey
Page 138 and 139: 11 Programmer's Guide This chapter
Page 140 and 141: Reserved Names The following are re
Page 142 and 143: 2. mylist = elementDom* This is a c
Page 144: symbol (\) followed by an ASCII cod
Page 150 and 151: For example, given trace domains li
Page 152 and 153: save("mydata.dba") the file mydata.
Page 154 and 155: domains file name, address age sex
Page 157: Tail recursion elimination is a tec
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Determinism, Non-determinism and Ho
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• The DOS linker, LlNK.EXE, must
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Compiling and Linking the Modules B
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so that the data segment addressed
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clauses dosver(VERSION): AX=L;8*2
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The Options Menu The Options pull-d
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Save Configuration S saves the curr
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ARITHMETIC FUNCTIONS AND PREDICATES
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• list of the possible flow patte
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date(Year, Month, Day ) (integer,in
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contained inside that window, the v
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less than or greater than zero, a b
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eadchar( CharVariable) (char) : (0)
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storage(StackSize,HeapSize, TrailSi
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f - Reals in fixed decimal notation
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Predicate and Database Section
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SYSTEM liMITS «arithmet
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ASCII Character Set (continued) Spe
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B Error Messages Following is a com
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600 Too many domain names 601 Too m
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C PLINK USE OF THE FILE PLINK.BAT P
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D PROWG.SYS The table below describ
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E Using Turbo Prolog with Turbo Pas
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F Glossary anonymous variable The v
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list A special sort of object consi
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Index A Anonymous Variable, 22-23 A
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p Pascal procedures. calling from T
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SlnBiCI The Organizer For The Compu
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Learn Pascal From The Folks Who Cre
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2VRBO PASCAt EDJ2OR7tDr.BOX It's Al
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NOTES
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NOTES
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NOTES
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Turbo Prolog

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