Re: Adding functionality to ARM BASIC

On 28 Jan 2009 20:51:02 +0000
jgh@xxxxxxxxxxxxxxxxxx (Jonathan Graham Harston) wrote:

nntp@xxxxxxxx wrote:
Out of interest, what do people actually use EVAL for? The only
thing

Creating variables at run-time:

Yeah, we've done this one. There really should be a syntax for it, and
Steve has suggested one.

Reading hex values:
start%=EVAL("&"+st$)

Clearly this should be done by VAL. (It is in Brandy.)

An assembler that uses BASIC variables as labels.
equ base &100 creates a variable called "base"
movb r0,(r1)base uses EVAL to find out what "base" is

This is internal to the interpreter's workings, and an implementation
issue. Not something the user cars about.

Calculated function call:
IF key%>=&80 AND key%<&9F:A%=EVAL("FN_"+STR$~key%)

Eugh, this is horrible. Firstly, there's most likely a better way of
expressing this code, and secondly there are more elegant ways of
implementing this. (Such as first-class functions or function
pointers.)

For it's original purpose:
INPUT "Enter function to graph: "func$
...
PLOT 69,x%,EVAL(func$)

And you'd certainly want no software past a little personal script ever
doing this.

B.

.

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