Fexl – Highly robust functional evaluation | Hacker News Reader

Fexl – Highly robust functional evaluation

github.com

10 pointsfexl3 comments

This version handles syntax errors, out of memory errors, and out of time errors, propagating them upward instead of halting with an error message, and reporting them in an orderly fashion at the end of the main program. Now the only calls to "die" are those which should never happen, i.e. they are pure assertions which are never expected to fail.

This allows for some very nice embedded calls to parsing and evaluation from within a Fexl program itself, which can always be expected to return to the caller instead of halting.

Ultimately I'm going to put a full-powered interpreter right on the web to allow arbitrary programs submitted from strangers, and this release is a necessary prerequisite for that.

Could you talk a little more about what `fexl` is? I don't see any obvious documentation beyond the README, which doesn't even seem to give a code sample; and, while 'functional evaluator' is an intriguing name, I don't know what it means.

Fexl is a functional programming language. I used the term "functional evaluation" because Fexl evaluates functions.

Here are a few code samples:

http://rosettacode.org/wiki/99_Bottles_of_Beer#Fexl

http://rosettacode.org/wiki/Fibonacci_sequence#Fexl

http://fexl.com/sample/

This one's a bit more involved:

http://fexl.com/demo/

You'll also find some code samples in the "test" directory:

https://github.com/chkoreff/Fexl/tree/master/src/test

The program a1.fxl there is the definitive test suite. The program a2.fxl reads what you type and echoes it back.

The samples above should help illustrate the nature of the language. Grammatically, it's very simple:

http://fexl.com/grammar/

For another quick illustration of the language, I'll give you a sample here:

    say "Hello"
    \x=(* 4.7 8.6)
    put "x = " put x nl

The output is:

    Hello
    x = 40.42

Reply on news.ycombinator.com