ReplaceInString

FindReplace$() function

A function that locates the first or all occurrence(s) of string B within string A and replaces it/them with string C.

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• This function works by taking as input an original string, a 'find' string, a 'replace' string,and either a 0 to specify single occurrence or 1 for all occurrences. It locates the position of 'find' within the original, assigns everything prior to 'find' to one variable, everything after to another, and then it modifies the original string to contain the value of 'replace' inbetween the before and after portions. If a 1 is specified for the replaceAll parameter, the function will loop until 'find' is no longer found in the modified original string. Test program included. This function is a variation of the StringChop$() function, which can be simulated here by specifying a blank 'replace' string and passing 1 for replaceAll.

orig$   = "This is the original string."
 
print orig$
print FindReplace$(orig$, "the", "NOT the", 0)
print : print
 
orig$   = "one two two four four four FOUR"
 
print "Original: "; orig$
print
print "Replacing first occurrence of 'four' with 'three'"
print "Replaced: "; FindReplace$(orig$,"four","three",0)
print
 
f$      = "four"
r$      = "three"
all     = 1
 
print "Replacing all occurrences of 'four' with 'three'"
print "Replaced: "; FindReplace$(orig$, f$, r$, all)
print
 
print "Replacing all spaces with commas"
print "Replaced: "; FindReplace$(orig$, " ", ",", all)
print : print
 
orig$ = "aaabbbccc"
 
print "Original: "; orig$
print
print "Replacing all occurrences of 'b' with 'bbb'"
print "Replaced: "; FindReplace$(orig$, "b", "bbb", all)
 
end
 
function FindReplace$(origString$,find$,replace$,replaceAll)
    'No point doing any work if the original string
    'and the 'find' string are blank...
    if ((origString$ <> "") and (find$ <> "")) then
        'Enter a loop
        do
            'Get the position of find$ within origString$
            'starting at previous value of fPos
            fPos = instr(origString$,find$,fPos)
 
            'If not found, we're done.
            if not(fPos) then
                FindReplace$ = origString$
                exit function
            end if
 
            'Get the lengths of find$ and replace$, place
            'everything before find$ in one variable, and
            'everything after it in another. Set origString$
            'itself to the new value in case all occurrences
            'are to be replaced. Finally, set the starting
            'position for the next iteration of the loop equal
            'to the start of post$ within the replaced string.
            fLen        =   len(find$)
            rLen        =   len(replace$)
            pre$        = left$(origString$, fPos - 1)
            post$       =  mid$(origString$, fPos + fLen)
            origString$ = pre$ + replace$ + post$
            fPos        = fPos + (rLen - fLen) + 1
 
        loop while replaceAll
        FindReplace$ = origString$
    end if
end function