[REBOL] [data type conversion] question
From: gerardcote:sympatico:ca at: 26-Mar-2004 14:10
Hi all,
While continuing my work about forthcoming REBOL tutorial for youngsters, I planned some
helper function to help them express maths
expression using the normal infix and precedence rules - like most calculators do. May
be this will not even be included at all with
the tutorial but it was a good excuse for me to investigate how I could learn more about
the parse word to create some translation
tool.
This worked for the most part and I went into some real knowledge that I will share here
soon and post the final products to the
official library to accompany other scripts found there about calculators and related
engines.
The only real question left came to me when I tried to call my calc with some real but
not well formed expressions using a block
instead of a string like in the following :
>> to-string [9 / 5 * 100 + 32] ; Here is the well formed version of
my test expression
== "9/5*100+32"
>> to-string [9/5 * 100 + 32] ; Here is the ill-formed version of
the same expression
** Syntax Error: Invalid date -- 9/5
** Near: (line 1) to-string [9/5 * 100 + 32]
>>
Finally my question is : Can REBOL be told to not evaluate each element of the block
contents I submit him when calling my function
but simply replaces the end delimiters [ ] for the appropriately ones " " ?
I would simply find more natural to let the user enter the conventional brackets [ ]
delimiters around the maths expression to
evaluate than remember to use the quotes " ". May be I could even afford for letting
the operator to use anyone of them if he
desires to do so.
In fact when using the quotes as delimiters I can afford the user to write his expressions
without having to insert spaces
everywhere since I control the expression parsing myself and this is what motivated me
in the first case to use the [ ] delimiters
also.
Don't forget that this is not to replace the conventional expression parser as found
in REBOL but to help younger people to start
learning without having to bother themselves with not standard maths expressions.
Thanks,
Gerard
