CHANGESTR.REX: Difference between revisions
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m (→the CHANGESTR source: changed a comment to reflect its IF statement.) |
m (→the CHANGESTR source: changed some comments (to align better for perusing).) |
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╚═════════════════════════════╝ │ │ │ │ │ │ ╚═══════════════════════════╝ |
╚═════════════════════════════╝ │ │ │ │ │ │ ╚═══════════════════════════╝ |
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↓ ↓ ↓ ↓ ↓ ↓ */ |
↓ ↓ ↓ ↓ ↓ ↓ */ |
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changestr: parse arg o,h,n,t,b,p, |
changestr: parse arg o,h,n,t,b,p, ,$ f /* ◄────────────────────┐*/ |
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/*T, B, P are optional ►─┘*/ |
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t=word(t 999999999, 1) /*maybe use the default? */ |
t=word(t 999999999, 1) /*maybe use the default? */ |
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b=word(b 1 , 1) /* " " " " */ |
b=word(b 1 , 1) /* " " " " */ |
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if \datatype(t, 'W') then signal syntax /*4th arg not an integer. */ |
if \datatype(t, 'W') then signal syntax /*4th arg not an integer. */ |
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if \datatype(b, 'W') then signal syntax /*5th " " " " */ |
if \datatype(b, 'W') then signal syntax /*5th " " " " */ |
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if \datatype(p, 'W') then signal syntax /*6th |
if \datatype(p, 'W') then signal syntax /*6th " " " " */ |
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if t<0 then signal syntax /*4th |
if t<0 then signal syntax /*4th " " non-negative.*/ |
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if b<1 then signal syntax /*5th |
if b<1 then signal syntax /*5th " " positive. */ |
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if p<1 then signal syntax /*6th " " " */ |
if p<1 then signal syntax /*6th " " " */ |
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L=length(o) /*length of OLD string. */ |
L=length(o) /*length of OLD string. */ |
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if L==0 & t\=0 then return n || h /*changing a null char? |
if L==0 & t\=0 then return n || h /*changing a [null] char? */ |
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/* [↓] check for position*/ |
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if p\=1 then do /*P¬=1? Then ajust F & H.*/ |
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f=left(h, min(p-1, length(h))) /*keep first part intact. */ |
f=left(h, min(p-1, length(h))) /*keep first part intact. */ |
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h=substr(h, p) /*only use this part of H.*/ |
h=substr(h, p) /*only use this part of H.*/ |
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if _=='' then return f || $ || y /*no more left, return. */ |
if _=='' then return f || $ || y /*no more left, return. */ |
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$=$ || y /*append the residual txt.*/ |
$=$ || y /*append the residual txt.*/ |
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/* [↓] check if too soon.*/ |
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if j<b then $=$ || o /*append OLD if too soon. */ |
if j<b then $=$ || o /*append OLD if too soon. */ |
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else do /*met the occurrence test.*/ |
else do /*met the occurrence test.*/ |
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$=$ || n /*append the NEW string.*/ |
$=$ || n /*append the NEW string.*/ |
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#=#+1 /*bump |
#=#+1 /*bump occurrence number. */ |
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end |
end /* [↑] append new string.*/ |
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end /*j*/ /*Note: most REXX ··· */ |
end /*j*/ /*Note: most REXX ··· */ |
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/* CHANGESTR BIFs only ···*/ |
/* CHANGESTR BIFs only ···*/ |
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Revision as of 21:26, 6 September 2016
the CHANGESTR function
This a RYO version of the REXX function changestr (change string).
It is included in some of the more modern Classic REXXes, but older versions of
Classic REXX don't have this function as a BIF (built-in-function).
This version of the changestr BIF has more functionality than the standard BIF.
the CHANGESTR source
<lang rexx>/*REXX program emulates the CHANGESTR BIF (built-in function) for older REXXes.*/ /*──────────── This version has more functionality: limit the number of changes. */ /*──────────── start of change occurrence#. */ /*──────────── start of change position. */
/* ╔═══════════════════════════ CHANGESTR function ════════════════════════╗
╔═╩═══════════════════════════════════════════════════════════════════════╩═╗
║ The CHANGESTR function is used to replace some or all occurrences of an ║
║ (old) string in a haystack with a new string. The changed string is ║
║ returned. If the haystack doesn't contain the old string, the ║
║ original haystack is returned. If the old string is a null string, ║
║ then the original string is prefixed with the new string. ║
║ ║
║ new string to be used ►──────┐ ┌──────◄ limit of # changes (times).║
║ original string (haystack) ►────┐ │ │ [default: ≈ one billion] ║
║ old string to be replaced ►──┐ │ │ │ ┌────◄ begin at this occurrence # ║
║ {O, H, and N can be null.} │ │ │ │ │ ┌──◄ start position (default=1) ║
╚═╦═════════════════════════════╗ │ │ │ │ │ │ ╔═══════════════════════════╦═╝
╚═════════════════════════════╝ │ │ │ │ │ │ ╚═══════════════════════════╝
↓ ↓ ↓ ↓ ↓ ↓ */
changestr: parse arg o,h,n,t,b,p, ,$ f /* ◄────────────────────┐*/
/*T, B, P are optional ►─┘*/
t=word(t 999999999, 1) /*maybe use the default? */
b=word(b 1 , 1) /* " " " " */
p=word(p 1 , 1) /* " " " " */
if arg() < 3 then signal syntax /*not enough arguments. */
if arg() > 6 then signal syntax /*too many arguments. */
if \datatype(t, 'W') then signal syntax /*4th arg not an integer. */
if \datatype(b, 'W') then signal syntax /*5th " " " " */
if \datatype(p, 'W') then signal syntax /*6th " " " " */
if t<0 then signal syntax /*4th " " non-negative.*/
if b<1 then signal syntax /*5th " " positive. */
if p<1 then signal syntax /*6th " " " */
L=length(o) /*length of OLD string. */
if L==0 & t\=0 then return n || h /*changing a [null] char? */
/* [↓] check for position*/
if p\=1 then do /*P¬=1? Then ajust F & H.*/
f=left(h, min(p-1, length(h))) /*keep first part intact. */
h=substr(h, p) /*only use this part of H.*/
end /*now, proceed as usual. */
#=0 /*# of changed occurrences*/
do j=1 while # < t /*keep changing, T times. */
parse var h y (o) _ +(L) h /*parse the haystack ··· */
if _== then return f || $ || y /*no more left, return. */
$=$ || y /*append the residual txt.*/
/* [↓] check if too soon.*/
if j<b then $=$ || o /*append OLD if too soon. */
else do /*met the occurrence test.*/
$=$ || n /*append the NEW string.*/
#=#+1 /*bump occurrence number. */
end /* [↑] append new string.*/
end /*j*/ /*Note: most REXX ··· */
/* CHANGESTR BIFs only ···*/
return f || $ || h /* support three options. */</lang>