From: Warren Brown <wkb@...>
Date: 2003-05-02T10:18:36+09:00
Subject: [PATCH] ljust, rjust, and center with pad string (was ljust, rjust...)

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> How about allowing `ljust' and `rjust' take an
> additional parameter (which defaults to the string
> " ") which specifies what it justifies with?
>
>   15.to_s.rjust(5)         #  -->  "   15"
>   15.to_s.rjust(5,'0')     #  -->  "00015"
>   15.to_s.rjust(5,'blue')  #  -->  "blu15"
>
> What do you think?

    I agree wholeheartedly.  The problem is made even worse by the fact that
'%05s' does *not* pad with leading zeros.  I have had to get around this
shortfall by doing things like:

foo.to_s.rjust(10).sub(/^ {,10}/,'0')

    Not only is this not very readable, but it is also fairly inefficient.

    I also find the lack of a padding string parameter very surprising since
every other language I have run across that implements padding functions
allows (or even requires) you to specify the padding string.  If you don't
believe me, do a Google search on "lpad function" and just *try* to find one
that doesn't :o)

    All in all, this would seem to be a real benefit to the language, is
easy to implement, and should not break any existing code.

    To expedite things, I have attached a patch that unifies the three
functions (ljust, rjust, and center) and adds this functionality.  The patch
can be applied to last night's snapshot.  I have performed a moderate amount
of testing on this patch and it seems OK.

    One quirk: a zero-length second parameter like "'x'.ljust(10,nil)" or
"'x'.ljust(10,'')" behaves like "'x'.ljust(10)".

    A generalized "justify" function similar to the one implemented in this
patch might be a nice addition to the language too.

    - Warren Brown

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--- string.c.orig	Sun Apr 27 09:13:25 2003=0A=
+++ string.c	Thu May  1 19:38:06 2003=0A=
@@ -3120,70 +3120,100 @@=0A=
     }=0A=
 }=0A=
 =0A=
+static VALUE=0A=
+rb_str_justify(argc, argv, str, jflag)=0A=
+    int argc;=0A=
+    VALUE *argv;=0A=
+    VALUE str;=0A=
+    char jflag;=0A=
+{=0A=
+    VALUE w;=0A=
+    long width, flen =3D 0;=0A=
+    VALUE res;=0A=
+    char *p, *pend, *f =3D " ";=0A=
+    long n;=0A=
+    VALUE pad;=0A=
+=0A=
+    if (rb_scan_args(argc, argv, "11", &w, &pad) =3D=3D 2) {=0A=
+        if (!NIL_P(pad)) {=0A=
+            StringValue(pad);=0A=
+            if (RSTRING(pad)->len > 0) {=0A=
+                f =3D RSTRING(pad)->ptr;=0A=
+                flen =3D RSTRING(pad)->len;=0A=
+            }=0A=
+        }=0A=
+    }=0A=
+    width =3D NUM2LONG(w);=0A=
+    if (width < 0 || RSTRING(str)->len >=3D width) return =
rb_str_dup(str);=0A=
+    res =3D rb_str_new5(str, 0, width);=0A=
+    p =3D RSTRING(res)->ptr;=0A=
+    if (jflag !=3D 'l') {=0A=
+        n =3D width - RSTRING(str)->len;=0A=
+        pend =3D p + ((jflag =3D=3D 'r') ? n : n/2);=0A=
+        if (flen <=3D 1) {=0A=
+            while (p < pend) {=0A=
+                *p++ =3D *f;=0A=
+            }=0A=
+        }=0A=
+        else {=0A=
+            char *q =3D f;=0A=
+            while (p + flen <=3D pend) {=0A=
+                memcpy(p,f,flen);=0A=
+                p +=3D flen;=0A=
+            }=0A=
+            while (p < pend) {=0A=
+                *p++ =3D *q++;=0A=
+            }=0A=
+        }=0A=
+    }=0A=
+    memcpy(p, RSTRING(str)->ptr, RSTRING(str)->len);=0A=
+    if (jflag !=3D 'r') {=0A=
+        p +=3D RSTRING(str)->len; pend =3D RSTRING(res)->ptr + width;=0A=
+        if (flen <=3D 1) {=0A=
+            while (p < pend) {=0A=
+                *p++ =3D *f;=0A=
+            }=0A=
+        }=0A=
+        else {=0A=
+            while (p + flen <=3D pend) {=0A=
+                memcpy(p,f,flen);=0A=
+                p +=3D flen;=0A=
+            }=0A=
+            while (p < pend) {=0A=
+                *p++ =3D *f++;=0A=
+            }=0A=
+        }=0A=
+    }=0A=
+    OBJ_INFECT(res, str);=0A=
+    if (flen > 0) OBJ_INFECT(res, pad);=0A=
+    return res;=0A=
+}=0A=
+=0A=
 static VALUE=0A=
-rb_str_ljust(str, w)=0A=
+rb_str_ljust(argc, argv, str)=0A=
+    int argc;=0A=
+    VALUE *argv;=0A=
     VALUE str;=0A=
-    VALUE w;=0A=
 {=0A=
-    long width =3D NUM2LONG(w);=0A=
-    VALUE res;=0A=
-    char *p, *pend;=0A=
-=0A=
-    if (width < 0 || RSTRING(str)->len >=3D width) return =
rb_str_dup(str);=0A=
-    res =3D rb_str_new5(str, 0, width);=0A=
-    memcpy(RSTRING(res)->ptr, RSTRING(str)->ptr, RSTRING(str)->len);=0A=
-    p =3D RSTRING(res)->ptr + RSTRING(str)->len; pend =3D =
RSTRING(res)->ptr + width;=0A=
-    while (p < pend) {=0A=
-	*p++ =3D ' ';=0A=
-    }=0A=
-    OBJ_INFECT(res, str);=0A=
-    return res;=0A=
+    return rb_str_justify(argc, argv, str, 'l');=0A=
 }=0A=
 =0A=
 static VALUE=0A=
-rb_str_rjust(str, w)=0A=
+rb_str_rjust(argc, argv, str)=0A=
+    int argc;=0A=
+    VALUE *argv;=0A=
     VALUE str;=0A=
-    VALUE w;=0A=
 {=0A=
-    long width =3D NUM2LONG(w);=0A=
-    VALUE res;=0A=
-    char *p, *pend;=0A=
-=0A=
-    if (width < 0 || RSTRING(str)->len >=3D width) return =
rb_str_dup(str);=0A=
-    res =3D rb_str_new5(str, 0, width);=0A=
-    p =3D RSTRING(res)->ptr; pend =3D p + width - RSTRING(str)->len;=0A=
-    while (p < pend) {=0A=
-	*p++ =3D ' ';=0A=
-    }=0A=
-    memcpy(pend, RSTRING(str)->ptr, RSTRING(str)->len);=0A=
-    OBJ_INFECT(res, str);=0A=
-    return res;=0A=
+    return rb_str_justify(argc, argv, str, 'r');=0A=
 }=0A=
 =0A=
 static VALUE=0A=
-rb_str_center(str, w)=0A=
+rb_str_center(argc, argv, str)=0A=
+    int argc;=0A=
+    VALUE *argv;=0A=
     VALUE str;=0A=
-    VALUE w;=0A=
 {=0A=
-    long width =3D NUM2LONG(w);=0A=
-    VALUE res;=0A=
-    char *p, *pend;=0A=
-    long n;=0A=
-=0A=
-    if (width < 0 || RSTRING(str)->len >=3D width) return =
rb_str_dup(str);=0A=
-    res =3D rb_str_new5(str, 0, width);=0A=
-    n =3D (width - RSTRING(str)->len)/2;=0A=
-    p =3D RSTRING(res)->ptr; pend =3D p + n;=0A=
-    while (p < pend) {=0A=
-	*p++ =3D ' ';=0A=
-    }=0A=
-    memcpy(pend, RSTRING(str)->ptr, RSTRING(str)->len);=0A=
-    p =3D pend + RSTRING(str)->len; pend =3D RSTRING(res)->ptr + width;=0A=
-    while (p < pend) {=0A=
-	*p++ =3D ' ';=0A=
-    }=0A=
-    OBJ_INFECT(res, str);=0A=
-    return res;=0A=
+    return rb_str_justify(argc, argv, str, 'c');=0A=
 }=0A=
 =0A=
 void=0A=
@@ -3265,9 +3295,9 @@=0A=
 =0A=
     rb_define_method(rb_cString, "scan", rb_str_scan, 1);=0A=
 =0A=
-    rb_define_method(rb_cString, "ljust", rb_str_ljust, 1);=0A=
-    rb_define_method(rb_cString, "rjust", rb_str_rjust, 1);=0A=
-    rb_define_method(rb_cString, "center", rb_str_center, 1);=0A=
+    rb_define_method(rb_cString, "ljust", rb_str_ljust, -1);=0A=
+    rb_define_method(rb_cString, "rjust", rb_str_rjust, -1);=0A=
+    rb_define_method(rb_cString, "center", rb_str_center, -1);=0A=
 =0A=
     rb_define_method(rb_cString, "sub", rb_str_sub, -1);=0A=
     rb_define_method(rb_cString, "gsub", rb_str_gsub, -1);=0A=

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