5 Programming

5.1 Input and Output

Input commands

read s

Opens the file whose name is string s for reading.

close

Closes the previously opened data file.

Standard input is used unless a data file is specified at command line invocation or open for reading.

Input functions

number(s)

Reads a number from current input.

string(s)

Reads a string from current input.

String s is used as a prompt.

Example:

l = number("Length? ")
w = number("Width? ")
draw rectangle(l, w)

When running in batch mode with no defined data file, the number function returns 0 and the string function returns the empty string.

Output commands

Output commands take a comma separated list of printable objects as arguments. Printable objects are strings, numbers, points and sets. They are formatted the same way as for conversion to string.

write s

Opens the file whose name is string s for writing. If the file exists, its content will be overwritten. Otherwise, it is created.

append s

Opens the file whose name is string s for appending. The file is created if it does not exist. Writing starts at the end of the file.

release

Closes previously opened result file.

print list

Writes list to current result file, or to standard output if none is open.

error list

Writes list to standard error stream.

output list

Writes list to output file. This may be useful to include low level PostScript or PSTricks command invocations.