Topic       : The GFA-Basic Compendium
Author      : GFA Systemtechnik GmbH
Version     : GFABasic.HYP v2.98 (12/31/2023)
Subject     : Documentation/Programming
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Index Size  : 28056
HCP-Version : 3
Compiled on : Atari
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View Ref-FileINSTR(a$,b$)
INSTR(a$,b$[,x])
INSTR([x,]a$,b$)

a$, b$: sexp
x: iexp

The function INSTR() searches the character string a$ for an occurrence of the
string b$. If x is specified, then the search begins at character position x in
a$, otherwise the whole string is searched.

If b$ is found within a$, the character position at which it begins is
returned, or, if it is not found the function returns zero (0). This value may
be assigned to a variable or used to determine whether a particular string was
present in a$. If a$ and b$ are both null strings (""), one (1) is returned.

The search goes from left to right.

Example:

    a$="GFA-Systemtechnik"
    x=INSTR(a$,"System")
    PRINT x,INSTR("GFA-BASIC","BASIC",6)

--> The numbers 5 and 0 appear on the screen.

    REPEAT
      a$=123456"
      b$=INKEY$
    UNTIL INSTR(a$,b$)

--> Waits until one of the specified keys has been pressed.

Memo: INSTR() has a bug which only appears if parameter 'x' is used.
      Use the following code listing instead:

FUNCTION instr(a$,b$,i&)
  $F%
  LOCAL v&
  v&=INSTR(a$,b$,i&)
  IF v&<i& !bug?
    v&=0
  ENDIF
  RETURN v&
ENDFUNC