Input/Output and File Operations

OUTPUT

• [pp ...] (pretty-print)
  Displays all the parameters exactly as they are. Texts will have quotation marks. Variables will be numbered from 0 upwards. Numbers, lists, pairs, everything will look exactly as it would look in the code.
• [write ...]
  The main output instruction. Displays parameters as follows:
  • Neither symbols nor floating-point numbers are displayed.
  • Texts are displayed without quotations.
  • Integer numbers are displayed as ASCII characters.
  • Lists of parameters are displayed as if using pp instruction. Therefore [write [1 2 3]] will display 123.
• [nl] - moves to the next line (newline).
  
• [show ...]
  Convenient macrodefinition. Check [list show] to see the full implementation.
  • Texts are displayed using write (without quotation marks).
  • All other parameters are dispalyed using pp.
  • Newline appears at the end.

INPUT

• [pr ...] (pretty-read)
  Reads Prolog element from the console. At least, tries.
• [read ...]
  Skips control and newline characters, then reads line of characters (until ENTER).
• [readln ...]
  Reads line of characters (until ENTER). Usefull if you type the input in the same line as the instruction during interactive session.

FILE OUTPUT

• [file_writer file "file_name"]
  Opens file specified by "file_name" for writing. If file doesn't exist then it is created. Newly opened fileis ready for writing using the file symbol as if it was a write instruction. If file is a variable, then a new anonymous symbols is created. Once this symbol is garbage-collected, the associated file is closed.
• [file ...]
  Works exactly as write but the output is written to the file instead. The file symbol must be associated with a physical file before use, as described above.
• [file] (without parameters) - closes the file.
• EXAMPLE 1: Creating a file called "some_file.txt" and writing "Hello World" with newline into it.
  
  • [create_atom "file"]
  • [file_writer file "some_file.txt"]
  • [file "Hello World\n"]
  • [file]
• EXAMPLE 2: Same as above but with implicit file closing by garbage collector.
  
  • [res [file_writer *file "some_file.txt"] [*file "Hello World\n"]]

FILE INPUT

• [file_reader file "file_name"]
  Opens file specified by "file_name" for reading. If the file doesn't exists then file_reader fails. If file is a variable, then an anonymous symbol is created. Once this symbols is garbage-collected, the associated file is closed.
• [file ...]
  Works exactly as pr but read the data from the file. It also has got a two parameter variant. The precise behaviour is:
  • [file *x] - same as pr.
  • [file "line" *x] - reads line of text (until newline).
  • [file "abcde..and-so-on" *x] - skips characters not included and then read as many characters as in the specified string. For example: "abcdefghijklmnopqrstuvwxyz" would read only a lower-case string.
• [file] (without parameters) - closes the file.

PROGRAM LOADERS

• [load "module_name.prc"] - loads specified module. If module is already loaded then it gets re-loaded.
• [consult "module_name.prc"] - same as load but displays the content of the loaded module on the console.
• [import "module_name.prc"] - loads specified module only if it is not already loaded.
• [batch "file_name"] - executes specified file as if it was a stored interactive session. The last instruction inside such a file should be [exit].