VAL incomplete

[zarsoft]

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 PROGRAM