On Sun, 22 Apr 2018 12:22:18 +0100, Gareth's Downstairs Computer wrote:

> However, it remains that my computing interest, resulting from my first
> real job 45 years ago, is to produce an interactive programming language
> (the interactivity of BASIC or FORTH) but that runs at the speed of
> compiled code and yet is fully reconstructable as the original source.
>
You probably already know this, but don't forget that many BASICs were in
reality compiled because RUN compiled into some more compact form and
then executed that. Many UNIX scripting languages are the same (AWK,
Perl, etc): they generate some form of P-code, which is then interpreted
by the runtime system. This seems to be a nice compromise, especially if
the code generated from each statement is the minimum needed to pass
variables to the previously compiled runtime system - the result could be
nearly as fast as optimised compiled code.

BTW, have you looked at JOSS or its derivatives, JEAN and FOCAL? JOSS was
one of the earlier interactive languages. JEAN ran on 1900 mainframes and
FOCAL was a DEC language.

There may be some nice ideas there, especially that like BASIC, JEAN line
numbers were treated as labels but, unlike BASIC, the line numbers were
real numbers. This made the editor simple since lines were always in
numeric order and, if you needed to add a line between 1.2 and 1.3 you
just gave it a line number of 1.25 Another nice trick was that all the
lines with the same integer part (known in JEAN as a 'part') could be
treated as a subroutine.

The main drawback was that conditions were suffixes to the statement they
controlled, so didn't have ELSE branches:

1.1 INPUT R as "Input a radius"
1.15 FINISH IF R = 0.0
1.2 DO PART 2 IF R > 0.0
1.25 GOTO 1.1
1.3 PRINT "Radii must be positive values"
1.4 GOTO 1.1
2.0 A = Pi * R * R
2.1 PRINT A "Area is %.%%"

.... or something like that. Its been 50 years since I last used JEAN.


--
Martin    | martin at
Gregorie  | gregorie dot org

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