Compiling in Runtime ---> EVAL+++

[Charles Pegge]

An Oxygen program can now compile strings of source code and run them without stopping. This allows EVAL functions to be implemented.

This is also a feature of Functional languages - being able to pass a function as a parameter of another function.
In our case, the function or expression is simply passed inside a string.

The compile() function is essentially a recursive operation and supports the full O2H Basic.

http://community.thinbasic.com/index.php?topic=2517

Compilefun3.tbasic
[code=thinbasic]

'RUNTIME COMPILING FROM STRINGS
'

uses "oxygen"
dim src as string

src = "
'
global as double x,y,z

function evaluate (s as string, b as long, e as long) as string
dim a,p=1 as long
dim v,u,cr as string
cr=chr(13) chr(10)
v=nuls 4000
mid v,p,s+cr+cr
p+=4+len s

a=compile `o2h `+s

if len (error) then print `runtime error: ` error : frees a : exit function

for x=b to e
call a
u=str(x)+chr(9)+str(y)+chr(13)+chr(10)
mid v,p,u : p+=len u
next
function=left v,p-1
frees a
end function

print evaluate `y=x*x*x`,1,10
print evaluate `y=sqrt x`,1,9

"





o2_basic src

'msgbox 0, o2_prep "o2h "+src

if len(o2_error) then
msgbox 0, o2_error : stop
end if

o2_exec

[/code]

[Petr Schreiber]

That is incredible Charles,

great Job!

So the recommended sequence is following?:

• assign code to string
• compile code and return its handle
• call compiled code by handle
• release compiled code by handle

Shocked Petr

[Charles Pegge]

Yes Petr, Right on!

The handle is really a BSTR containing the compiled code. So it is explicitly freed afterwards in this case.

[zlatkoAB]

Charles you are amazing man

[ErosOlmi]

Yes, that's really amazing.

[kryton9]

Ok we need to start calling Charles-- Merlin after the famous Wizard. And what is all the more amazing is that he mentioned doing this yesterday or the day before and in the meantime added so many other features, like line numbers. Eros and Charles must be related somehow in lineage being both so super fast in complex code and feature development!!