Interface: Standard IO

With the option '--interface stdio', the Arrp compiler generates C++ code for an executable with a simple generic interface.

Inputs and outputs are mapped to standard input and output channels (terminal, pipes, etc.) or to files. Small amounts of input data can also be provided using command line options.

Input and output can use various formats (currently text or native binary).

A Quick Example

For example, consider the following Arrp code:

input x : [~]int;
output y = x * 2;

Assuming the above code is in a file program.arrp, the following command generates a few C++ header files and a main file name "program-stdio-main.cpp":

arrp program.arrp --interface stdio --output program

This code can be compiled into an executable "program" with a C++ compiler, for example g++ (considering Arrp headers are installed in a standard location):

g++ program-stdio-main.cpp -o program

By default, this program will use the standard input channel for stream x and the standard output channel for stream y, both using the text format.

Running ./program -h will print help on other options.

When running ./program in a terminal, it waits for us to type in some input. After typing some input and a line break, the program responds with the corresponding output, each element on a separate line. A terminal session might look like this: 

input  ->  1
output ->  2
input  ->  5
output ->  10
input  ->  3 -2 6
output ->  6
output ->  -4
output ->  12

Input Sources and Output Destinations

Running ./program -h will print help on all the options and a list of input and output names.

If an input requires a small amount of data, it can be provided literally on the command line. For example, assuming program contains input some_option : [3]int, the input can be set like this: 

./program some_option="2 5 6"

Literal values like this use the text format.

To instruct the program to read an input or write an output to a file, provide the file name like this: 

./program some_input=some_file

In place of the file name, "pipe" can be used to explicitly use the standard input or output channel: 

./program some_input=pipe

Standard channels and files can use any of the available formats.

If there is a single input/output or a single stream-type input/output, it will automatically use the standard input/output channel.

Input and Output Formats

Different formats can be specified for inputs and outputs using standard channels and files.

Unless otherwise specified, all inputs and outputs use the text format.

A different default format can be specified with the -f option: 

./program -f raw

A format for an individual input or output can be specified following a colon: 

./program some_input=pipe:raw

In all cases, array elements are read and written as a sequence following the lexicographical order of array indices, e.g. for a 2 dimensional array: (0,0), (0,1), (0,2), ... (1,0), (1,1), ...

These are the available formats:

Buffering

To improve performance, the generated executable may read and write data in larger chunks and buffer it.

The buffer size can be adjusted using the -b option. For example, to set it to 64 elements: 

./program -b 64

When an input is buffered, the program reads from the source in chunks equal to the size of the buffer. It will read the next chunk only when more data is required to produce output.

When an output is buffered, the program will write to the destination in chunks equal to the size of the buffer. It will write a chunk as soon as that amount of new data is produced.

Currently, buffering is enabled only for inputs and outputs in raw format, and when the chosen buffer size is considerably larger than the amount of data the program normally consumes and produces at one time. Mind that (depending on the compilation options) a multi-dimensional stream may produce or consume an entire slice at a time - meaning a group of elements with the same index in the first dimension.