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.