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+---- Thread: VAL incomplete (/showthread.php?tid=2427)
VAL incomplete - zarsoft - 2023-06-24
In ZX SPECTRUM:
LET x = 2
PRINT VAL "2*x"
Prints 4
But on the compiler gives 0
How about adding variables from "a" to "z" in VAL?
RE: VAL incomplete - boriel - 2023-06-26
This cannot be done in compiled BASIC. VAL "2*x" will need the ROM VAL, which calls the BASIC interpreter. This will need to store the variables in Sinclair BASIC Format which takes more space and is slow so the ROM interpreter will find the variable "x" in the BASIC Variables region.
Currently, a compiled variable like that of the example takes 1 byte (just the space needed to store the number). For Sinclair BASIC it will always be a Float (5 bytes, and slow) + the variable name "x" encoded in another region, etc.
So VAL here will behave as most BASICs, convert a STRING to a number or return 0 if it cannot decode it (indeed Sinclair BASIC VAL is very powerful).
There is a library function to call the BASIC interpreter, BTW, but it won't work in this case because it still needs the "x" variable.
RE: VAL incomplete - zarsoft - 2023-06-26
(2023-06-26, 08:32 AM)boriel Wrote: VAL "2*x" will need the ROM VAL.
Then, I will do it the hard way:
LET X = 5
LET F$ = "2*X"
LET G$ = VALx$( F$)
( G$ = "2*5" )
PRINT VAL G$
(result = 10)
Code:
' PROGRAM VALx
' (c) ZarSoft 2023 Pascalated Boriel ZX BASIC
' Written by Ze Oliveira
#include <input.bas> ' number = VAL INPUT(12)
#include <screen.bas> ' SCREEN$ function
#include <attr.bas> ' ATTR function
'--- Pascalated Boriel ---
#define PROGRAM REM
#define BEGIN REM
'#define CONST CONST
#define VAR DIM
#define INTEGER LONG
#define REAL FLOAT
#define CHAR STRING
'#define STRING STRING
#define BOOLEAN UBYTE
#define TYPE AS
'#define WHILE WHILE
#define REPEAT DO
#define UNTIL LOOP UNTIL
#define PROCEDURE SUB
CONST TRUE TYPE BOOLEAN = 1
CONST FALSE TYPE BOOLEAN = 0
PROGRAM VALx
VAR X TYPE REAL
VAR Y TYPE REAL
FUNCTION VARaz (V$ TYPE STRING) TYPE REAL
VAR R TYPE REAL
IF V$ = "Z"
R = Z
ELSE IF V$ = "Y"
R = Y
ELSE IF V$ = "X"
R = X
ENDIF
RETURN R
END FUNCTION
FUNCTION VALx$ (S$ TYPE STRING) TYPE STRING
VAR R$ TYPE STRING
R$ = ""
FOR i = 0 TO LEN S$ -1
IF S$(i) >= "A"
LET R$ = R$ + STR$ VARaz( S$(i) )
ELSE
LET R$ = R$ + S$(i)
ENDIF
NEXT i
RETURN R$
END FUNCTION
PROGRAM VALx
VAR x,y,z TYPE INTEGER
VAR F$ TYPE STRING
VAR G$ TYPE STRING
VAR sx,sy TYPE REAL
VAR sx0,sy0 TYPE REAL
VAR first TYPE BOOLEAN
LET F$ = "9/(1+8*X*X+8*Y*Y)"
FOR y = -3 TO 0
LET first = TRUE
FOR x = -5 TO 5
LET X = x*0.5
LET Y = y*0.5
LET G$ = VALx(F$)
PRINT AT 0,0;"F(x,y)=";G$,,
LET z = VAL(G$)
LET sx = 120 + 20*x - 2.5*y
LET sy = 75 + 6*y + 2.5*x + 10.1*z
IF first
first = FALSE
PLOT sx,sy
ELSE
DRAW sx-sx0,sy-sy0
ENDIF
LET sx0 = sx
LET sy0 = sy
NEXT x
NEXT y
END PROGRAMRE: VAL incomplete - zarsoft - 2023-06-26
(2023-06-26, 10:25 AM)zarsoft Wrote: Then, I will do it the hard way:
I have updated
https://forum.boriel.com/showthread.php?tid=2428