## To build:

``` <!---sh-->
    make all
```


### Bugs and (Mis)features:

The current status of this entry is:

> **STATUS: INABIAF - please DO NOT fix**

For more detailed information see [1989/robison in bugs.html](../../bugs.html#1989_robison).


## To use:

``` <!---sh-->
    ./robison
    # enter valid expressions
```


## Try:

``` <!---sh-->
    ./robison
    11x10
    # enter other expressions

    ./try.sh

    echo 100 / 100 | ./robison # <-- what happens here ?
```

**NOTE**: This program will very likely crash or break into tiny bits :-) if you
feed it numbers with non-binary digits. This, as you might notice if you try one
of the above commands, can happen with other input as well. If you wish to
understand why this happens check the source code.


## Judges' remarks:

Sites with punch card facilities will be happy to note that
the source deck can be re-collated with an ASCII sort.

Note that this program uses only a small subset of the
constructs that the C language supports.

For an interesting document on APL, see
<https://computerhistory.org/blog/the-apl-programming-language-source-code/>.


## Author's remarks:

This program is a handy picoAPL interpreter written in `C--`.  It
outputs the evaluation of an
[APL](https://en.wikipedia.org/wiki/APL_&lpar;programming_language&rpar;) expression from standard
input.  Functions are limited to dyadic `+`,`-`,`x`, and unary `-`;
numerals must be binary.  Parentheses may be used for
grouping.  For example:

```
    101x111-100
```

prints:

```
    1111
```

That is `5x(7-4)` is `15`.  (APL groups from right to left.)
Extending it to the full APL language should be trivial.

The `C--` language improves the C language by removing superfluous
and confusing features: arithmetic, logical operations, shifts,
relational operators, address-of, and flow control.  In fact, the only
expressions retained are function calls, indirection, array
assignments, the ',' operator, and `sizeof`.  Despite these
restrictions, the `C--` program does arithmetic on arbitrarily
large binary numbers.

To obtain a `C--` reference, simply rip out the irrelevant pages
from your K&R C manual.  To obtain a `C--` compiler, simply rip
out the irrelevant bytes from your `cc` compiler.


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