VAL incomplete - Printable Version

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