6.11 Inputs and Outputs

6.11.1 end, quit

end, quit

:: Close the currently reading file. At the top level, terminate the Asir session.

• These two functions take no arguments. These functions can be called without a ‘()’. Either function close the current input file. This means the termination of the Asir session at the top level.
• An input file will be automatically closed if it is read to its end. However, if no end$ is written at the last of the input file, the control will be returned to the top level and Asir will be waiting for an input without any prompting. Thus, in order to avoid confusion, putting a end$ at the last line of the input file is strongly recommended.

[6] quit;
%

References

load.

6.11.2 load

load("filename")

:: Reads a program file filename.

return

(1|0)

filename

file (path) name

• See User language Asir for practical programming. Since text files are read through cpp, the user can use, as in C programs, #include and #define in Asir program source codes. The cpp which is installed to the system with a C compler is used in the unix version. The mcpp http://mcpp.sourceforge.net is used in the Windows version. Note that the length of a line has a limit for an input mcpp. The OpenXM/bin/ox_cpp is used in the unix/OpenXM version (including cfep/asir for MacOS X). This is the cpp distributed with the Portable C compiler http://pcc.ludd.ltu.se.
• It returns 1 if the designated file exists, 0 otherwise.
• If the filename begins with ‘/’, it is understood as an absolute path name; with ‘.’, relative path name from current directory; otherwise, the file is searched first from directories assigned to an environmental variable ASIRLOADPATH, then if the search ends up in failure, the standard library directory (or directories assigned to ASIR_LIBDIR) shall be searched. On Windows, get_rootdir()/lib is searched if ASIR_LIBDIR is not set.
• We recommend to write an end command at the last line of your program. If not, Asir will not give you a prompt after it will have executed load command. (Escape with an interrupt character (Interruption), if you have lost yourself.) Even in such a situation, Asir itself is still ready to read keyboard inputs as usual. It is, however, embarrassing and may cause other errors. Therefore, to put an end$ at the last line is desirable. (Command end; will work as well, but it also returns and displays verbose.)
• On Windows one has to use ‘/’ as the separator of directory names.

References

end, quit, which, get_rootdir.

6.11.3 which

which("filename")

:: This returns the path name for the filename which load() will read.

return

path name

filename

filename (path name) or 0

• This function searches directory trees according to the same procedure as load() will do. Then, returns a string, the path name to the file if the named file exists; 0 unless otherwise.
• For details of searching procedure, refer to the description about load().
• On Windows one has to use ‘/’ as the separator of directory names.

[0] which("gr");               
./gb/gr
[1] which("/usr/local/lib/gr");
0
[2] which("/usr/local/lib/asir/gr");
/usr/local/lib/asir/gr

References

load.

6.11.4 output

output(["filename"])

:: Writes the return values and prompt onto file filename.

return

1

filename

filename

• Standard output stream of Asir is redirected to the specified file. While Asir is writing its outputs onto a file, no outputs, except for keyboard inputs and some of error messages, are written onto the standard output. (You cannot see the result on the display.)
• To direct the Asir outputs to the standard output, issue the command without argument, i.e., output().
• If the specified file already exists, new outputs will be added to the tail of the file. If not, a file is newly created and the outputs will be written onto the file.
• When file name is specified without double quotes (""), or when protected file is specified, an error occurs and the system returns to the top level.
• If you want to write inputs from the key board onto the file as well as Asir outputs, put command ctrl("echo",1), and then redirect the standard output to your desired file.
• Contents which are written onto the standard error output, CPU time etc., are not written onto the file.
• Reading and writing algebraic expressions which contain neither functional forms nor unknown coefficients (vtype() References) are performed more efficiently, with respect to both time and space, by bload() and bsave().
• On Windows one has to use ‘/’ as the separator of directory names.

[83] output("afo");
fctr(x^2-y^2);
print("afo");
output();
1
[87] quit;
% cat afo
1
[84] [[1,1],[x+y,1],[x-y,1]]
[85] afo
0
[86]

References

ctrl, bsave, bload.

6.11.5 bsave, bload

bsave(obj,"filename")

:: This function writes obj onto filename in binary form.

bload("filename")

:: This function reads an expression from filename in binary form.

return

bsave() : 1, bload() : the expression read

obj

arbitrary expression which does not contain neither function forms nor unknown coefficients.

filename

filename

• Function bsave() writes an object onto a file in its internal form (not exact internal form but very similar). Function bload() read the expression from files which is written by bsave(). Current implementation support arbitrary expressions, including lists, arrays (i.e., vectors and matrices), except for function forms and unknown coefficients (vtype() References.)
• The parser is activated to retrieve expressions written by output() , whereas internal forms are directly reconstructed by bload() from the bsave()’ed object in the file. The latter is much more efficient with respect to both time and space.
• It may happen that the variable ordering at reading is changed from that at writing. In such a case, the variable ordering in the internal expression is automatically rearranged according to the current variable ordering.
• On Windows one has to use ‘/’ as the separator of directory names.

[0] A=(x+y+z+u+v+w)^20$
[1] bsave(A,"afo");
1
[2] B = bload("afo")$
[3] A == B;
1
[4] X=(x+y)^2; 
x^2+2*y*x+y^2
[5] bsave(X,"afo")$
[6] quit;
% asir
[0] ord([y,x])$    
[1] bload("afo");
y^2+2*x*y+x^2

References

output.

6.11.6 bload27

bload27("filename")

:: Reads bsaved file created by older version of Asir.

return

expression read

filename

filename

• In older versions an arbitrary precision integer is represented as an array of 27bit integers. In the current version it is represented as an array of 32bit integers. By this incompatibility the bsaved file created by older versions cannot be read in the current version by bload. bload27 is used to read such files.
• On Windows one has to use ‘/’ as the separator of directory names.

References

bsave, bload.

6.11.7 print

print(obj [,nl])

:: Displays (or outputs) obj.

return

0

obj

arbitrary

nl

flag (arbitrary)

• Displays (or outputs) obj.
• It normally adds linefeed code to cause the cursor moving to the next line. If 0 or 2 is given as the second argument, it does not add a linefeed. If the second argument is 0, the output is simply written in the buffer. If the second argument is 2, the output is flushed.
• The return value of this function is 0. If command print(rat); is performed at the top level, first the value of rat will be printed, followed by a linefeed, followed by a 0 which is the value of the function and followed by a linefeed and the next prompt. (If the command is terminated by a ‘$’, e.g., print(rat)$, The last 0 will not be printed. )
• Formatted outputs are not currently supported. If one wishes to output multiple objects by a single print() command, use list like [obj1,...], which is not so beautiful, but convenient to minimize programming efforts.

[8] def cat(L) { while ( L != [] ) { print(car(L),0); L = cdr(L);}
print(""); }
[9] cat([xyz,123,"gahaha"])$
xyz123gahaha

6.11.8 access

access(file)

:: testing an existence of file.

return

(1|0)

file

filename

6.11.9 remove_file

remove_file(file)

:: Delete an file file.

return

1

file

filename

6.11.10 open_file, close_file, get_line, get_byte, put_byte, purge_stdin

open_file("filename"[,"mode"])

:: Opens filename for reading.

close_file(num)

:: Closes the file indicated by a descriptor num.

get_line([num])

:: Reads a line from the file indicated by a descriptor num.

get_byte(num)

:: Reads a byte from the file indicated by a descriptor num.

put_byte(num,c)

:: Writes a byte c to the file indicated by a descriptor num.

purge_stdin()

:: Clears the buffer for the standard input.

return

open_file() : integer (fild id); close_file() : 1; get_line() : string; get_byte(), put_byte() : integer

filename

file (path) name

mode

string

num

non-negative integer (file descriptor)

• open_file() opens a file. If mode is not specified, a file is opened for reading. If mode is specified, it is used as the mode specification for C standard I/O function fopen(). For example "w" requests that the file is truncated to zero length or created for writing. "a" requests that the file is opened for writing or created if it does not exist. The stream pointer is set at the end of the file. If successful, it returns a non-negative integer as the file descriptor. Otherwise the system error function is called. Unnecessary files should be closed by close_file(). If the special file name unix://stdin or unix://stdout or unix://stderr is given, it returns the file descriptor for the standard input or the standard output or the standard error stream respectively. The mode argument is ignored in this case.
• get_line() reads a line from an opened file and returns the line as a string. If no argument is supplied, it reads a line from the standard input.
• get_byte() reads a byte from an opened file and returns the it as an integer.
• put_byte() writes a byte from an opened file and returns the the byte as an integer.
• A get_line() call after reading the end of file returns an integer 0.
• Strings can be converted into internal forms with string manipulation functions such as sub_str(), eval_str().
• purge_stdin() clears the buffer for the standard input. When a function receives a character string from get_line(), this functions should be called in advance in order to avoid an incorrect behavior which is caused by the characters already exists in the buffer.

[185] Id = open_file("test");
0
[186] get_line(Id);
12345

[187] get_line(Id);
67890

[188] get_line(Id);
0
[189] type(@@);
0
[190] close_file(Id);
1
[191] open_file("test");
1
[192] get_line(1);   
12345

[193] get_byte(1);
54                   /* the ASCII code of '6' */
[194] get_line(1);
7890                 /* the rest of the last line */
[195] def test() { return get_line(); }
[196] def test1() { purge_stdin(); return get_line(); }
[197] test();
                     /* a remaining newline character has been read */
                     /* returns immediately */
[198] test1();
123;                 /* input from a keyboard */
123;                 /* returned value */

[199] 

References

eval_str, str_len, str_chr, sub_str.

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