CHANGESTR.REX
<lang rexx>/*╔══════════════════════════════╗ CHANGESTR ╔═════════════════════════╗ ╔═╩══════════════════════════════╝ function ╚═════════════════════════╩═╗ ║ new string to be used──────────┐ ┌─────limit of # changes (times)║ ║ original string (haystack)────────┐ │ │ [default: ≈ one billian]║ ║ old string to be changed───┐ │ │ │ ┌───begin at this occurance #.║ ║ {O, H, and N can be null.} │ │ │ │ │ [default: 1st occurrance]║ ╚═╦════════════════════════════╗ │ │ │ │ │ ╔═══════════════════════╦═╝
╚════════════════════════════╝ ↓ ↓ ↓ ↓ ↓ ╚═══════════════════════╝*/
changestr: procedure; parse arg o,h,n,t,b /* T and B are optional.*/ $= /*$: the returned string.*/ t=word(t 999999999 , 1) /*maybe use the default? */ b=word(b 1 , 1) /* " " " " */ w=length(o) /*length of OLD string.*/ if w==0 & t\=0 then return n || h /*changing a null char ? */
- =0 /*# of changed occurances*/
do j=1 until # >= t /*keep changing, T times.*/ parse var h y (o) _ +(w) h /*parse the string ... */ if _== then return $ || y /*no more left, return. */ if j<b then $=$ || y || o /*didn't meet begin at ? */ else do $=$ || y || n /*build new STR from S. */ #=#+1 /*bump occurance number. */ end end /*j*/ /*Most REXX BIFs only ···*/
return $ || h /* support three options.*/</lang>