compar.c

/**********************************************************************

  compar.c -

  $Author$
  created at: Thu Aug 26 14:39:48 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto

**********************************************************************/

#include "id.h"
#include "internal.h"
#include "internal/compar.h"
#include "internal/error.h"
#include "internal/vm.h"
#include "ruby/ruby.h"

VALUE rb_mComparable;

static VALUE
rb_cmp(VALUE x, VALUE y)
{
    return rb_funcallv(x, idCmp, 1, &y);
}

void
rb_cmperr(VALUE x, VALUE y)
{
    VALUE classname;

    if (SPECIAL_CONST_P(y) || BUILTIN_TYPE(y) == T_FLOAT) {
        classname = rb_inspect(y);
    }
    else {
        classname = rb_obj_class(y);
    }
    rb_raise(rb_eArgError, "comparison of %"PRIsVALUE" with %"PRIsVALUE" failed",
             rb_obj_class(x), classname);
}

static VALUE
invcmp_recursive(VALUE x, VALUE y, int recursive)
{
    if (recursive) return Qnil;
    return rb_cmp(y, x);
}

VALUE
rb_invcmp(VALUE x, VALUE y)
{
    VALUE invcmp = rb_exec_recursive(invcmp_recursive, x, y);
    if (NIL_OR_UNDEF_P(invcmp)) {
        return Qnil;
    }
    else {
        int result = -rb_cmpint(invcmp, x, y);
        return INT2FIX(result);
    }
}

static VALUE
cmp_eq_recursive(VALUE arg1, VALUE arg2, int recursive)
{
    if (recursive) return Qnil;
    return rb_cmp(arg1, arg2);
}

/*
 *  call-seq:
 *     obj == other    -> true or false
 *
 *  Compares two objects based on the receiver's <code><=></code>
 *  method, returning true if it returns 0. Also returns true if
 *  _obj_ and _other_ are the same object.
 */

static VALUE
cmp_equal(VALUE x, VALUE y)
{
    VALUE c;
    if (x == y) return Qtrue;

    c = rb_exec_recursive_paired_outer(cmp_eq_recursive, x, y, y);

    if (NIL_P(c)) return Qfalse;
    return RBOOL(rb_cmpint(c, x, y) == 0);
}

static int
cmpint(VALUE x, VALUE y)
{
    return rb_cmpint(rb_cmp(x, y), x, y);
}

/*
 *  call-seq:
 *     obj > other    -> true or false
 *
 *  Compares two objects based on the receiver's <code><=></code>
 *  method, returning true if it returns a value greater than 0.
 */

static VALUE
cmp_gt(VALUE x, VALUE y)
{
    return RBOOL(cmpint(x, y) > 0);
}

/*
 *  call-seq:
 *     obj >= other    -> true or false
 *
 *  Compares two objects based on the receiver's <code><=></code>
 *  method, returning true if it returns a value greater than or equal to 0.
 */

static VALUE
cmp_ge(VALUE x, VALUE y)
{
    return RBOOL(cmpint(x, y) >= 0);
}

/*
 *  call-seq:
 *     obj < other    -> true or false
 *
 *  Compares two objects based on the receiver's <code><=></code>
 *  method, returning true if it returns a value less than 0.
 */

static VALUE
cmp_lt(VALUE x, VALUE y)
{
    return RBOOL(cmpint(x, y) < 0);
}

/*
 *  call-seq:
 *     obj <= other    -> true or false
 *
 *  Compares two objects based on the receiver's <code><=></code>
 *  method, returning true if it returns a value less than or equal to 0.
 */

static VALUE
cmp_le(VALUE x, VALUE y)
{
    return RBOOL(cmpint(x, y) <= 0);
}

/*
 *  call-seq:
 *     obj.between?(min, max)    -> true or false
 *
 *  Returns <code>false</code> if _obj_ <code><=></code> _min_ is less
 *  than zero or if _obj_ <code><=></code> _max_ is greater than zero,
 *  <code>true</code> otherwise.
 *
 *     3.between?(1, 5)               #=> true
 *     6.between?(1, 5)               #=> false
 *     'cat'.between?('ant', 'dog')   #=> true
 *     'gnu'.between?('ant', 'dog')   #=> false
 *
 */

static VALUE
cmp_between(VALUE x, VALUE min, VALUE max)
{
    return RBOOL((cmpint(x, min) >= 0 && cmpint(x, max) <= 0));
}

/*
 *  call-seq:
 *     obj.clamp(min, max) ->  obj
 *     obj.clamp(range)    ->  obj
 *
 * In <code>(min, max)</code> form, returns _min_ if _obj_
 * <code><=></code> _min_ is less than zero, _max_ if _obj_
 * <code><=></code> _max_ is greater than zero, and _obj_
 * otherwise.
 *
 *     12.clamp(0, 100)         #=> 12
 *     523.clamp(0, 100)        #=> 100
 *     -3.123.clamp(0, 100)     #=> 0
 *
 *     'd'.clamp('a', 'f')      #=> 'd'
 *     'z'.clamp('a', 'f')      #=> 'f'
 *
 * In <code>(range)</code> form, returns _range.begin_ if _obj_
 * <code><=></code> _range.begin_ is less than zero, _range.end_
 * if _obj_ <code><=></code> _range.end_ is greater than zero, and
 * _obj_ otherwise.
 *
 *     12.clamp(0..100)         #=> 12
 *     523.clamp(0..100)        #=> 100
 *     -3.123.clamp(0..100)     #=> 0
 *
 *     'd'.clamp('a'..'f')      #=> 'd'
 *     'z'.clamp('a'..'f')      #=> 'f'
 *
 * If _range.begin_ is +nil+, it is considered smaller than _obj_,
 * and if _range.end_ is +nil+, it is considered greater than
 * _obj_.
 *
 *     -20.clamp(0..)           #=> 0
 *     523.clamp(..100)         #=> 100
 *
 * When _range.end_ is excluded and not +nil+, an exception is
 * raised.
 *
 *     100.clamp(0...100)       # ArgumentError
 */

static VALUE
cmp_clamp(int argc, VALUE *argv, VALUE x)
{
    VALUE min, max;
    int c, excl = 0;

    if (rb_scan_args(argc, argv, "11", &min, &max) == 1) {
        VALUE range = min;
        if (!rb_range_values(range, &min, &max, &excl)) {
            rb_raise(rb_eTypeError, "wrong argument type %s (expected Range)",
                     rb_builtin_class_name(range));
        }
        if (!NIL_P(max)) {
            if (excl) rb_raise(rb_eArgError, "cannot clamp with an exclusive range");
        }
    }
    if (!NIL_P(min) && !NIL_P(max) && cmpint(min, max) > 0) {
        rb_raise(rb_eArgError, "min argument must be less than or equal to max argument");
    }

    if (!NIL_P(min)) {
        c = cmpint(x, min);
        if (c == 0) return x;
        if (c < 0) return min;
    }
    if (!NIL_P(max)) {
        c = cmpint(x, max);
        if (c > 0) return max;
    }
    return x;
}

/*
 *  The Comparable mixin is used by classes whose objects may be
 *  ordered. The class must define the <code><=></code> operator,
 *  which compares the receiver against another object, returning a
 *  value less than 0, returning 0, or returning a value greater than 0,
 *  depending on whether the receiver is less than, equal to,
 *  or greater than the other object. If the other object is not
 *  comparable then the <code><=></code> operator should return +nil+.
 *  Comparable uses <code><=></code> to implement the conventional
 *  comparison operators (<code><</code>, <code><=</code>,
 *  <code>==</code>, <code>>=</code>, and <code>></code>) and the
 *  method <code>between?</code>.
 *
 *     class SizeMatters
 *       include Comparable
 *       attr :str
 *       def <=>(other)
 *         str.size <=> other.str.size
 *       end
 *       def initialize(str)
 *         @str = str
 *       end
 *       def inspect
 *         @str
 *       end
 *     end
 *
 *     s1 = SizeMatters.new("Z")
 *     s2 = SizeMatters.new("YY")
 *     s3 = SizeMatters.new("XXX")
 *     s4 = SizeMatters.new("WWWW")
 *     s5 = SizeMatters.new("VVVVV")
 *
 *     s1 < s2                       #=> true
 *     s4.between?(s1, s3)           #=> false
 *     s4.between?(s3, s5)           #=> true
 *     [ s3, s2, s5, s4, s1 ].sort   #=> [Z, YY, XXX, WWWW, VVVVV]
 *
 *  == What's Here
 *
 *  \Module \Comparable provides these methods, all of which use method <tt><=></tt>:
 *
 *  - #<: Returns whether +self+ is less than the given object.
 *  - #<=: Returns whether +self+ is less than or equal to the given object.
 *  - #==: Returns whether +self+ is equal to the given object.
 *  - #>: Returns whether +self+ is greater than the given object.
 *  - #>=: Returns whether +self+ is greater than or equal to the given object.
 *  - #between?: Returns +true+ if +self+ is between two given objects.
 *  - #clamp: For given objects +min+ and +max+, or range <tt>(min..max)</tt>, returns:
 *
 *    - +min+ if <tt>(self <=> min) < 0</tt>.
 *    - +max+ if <tt>(self <=> max) > 0</tt>.
 *    - +self+ otherwise.
 *
 */

void
Init_Comparable(void)
{
    rb_mComparable = rb_define_module("Comparable");
    rb_define_method(rb_mComparable, "==", cmp_equal, 1);
    rb_define_method(rb_mComparable, ">", cmp_gt, 1);
    rb_define_method(rb_mComparable, ">=", cmp_ge, 1);
    rb_define_method(rb_mComparable, "<", cmp_lt, 1);
    rb_define_method(rb_mComparable, "<=", cmp_le, 1);
    rb_define_method(rb_mComparable, "between?", cmp_between, 2);
    rb_define_method(rb_mComparable, "clamp", cmp_clamp, -1);
}