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Numeric#step
static VALUE
num_step(int argc, VALUE *argv, VALUE from)
{
VALUE to, step;
int desc, inf;
if (!rb_block_given_p()) {
VALUE by = Qundef;
num_step_extract_args(argc, argv, &to, &step, &by);
if (!UNDEF_P(by)) {
step = by;
}
if (NIL_P(step)) {
step = INT2FIX(1);
}
else if (rb_equal(step, INT2FIX(0))) {
rb_raise(rb_eArgError, "step can't be 0");
}
if ((NIL_P(to) || rb_obj_is_kind_of(to, rb_cNumeric)) &&
rb_obj_is_kind_of(step, rb_cNumeric)) {
return rb_arith_seq_new(from, ID2SYM(rb_frame_this_func()), argc, argv,
num_step_size, from, to, step, FALSE);
}
return SIZED_ENUMERATOR_KW(from, 2, ((VALUE [2]){to, step}), num_step_size, FALSE);
}
desc = num_step_scan_args(argc, argv, &to, &step, TRUE, FALSE);
if (rb_equal(step, INT2FIX(0))) {
inf = 1;
}
else if (RB_FLOAT_TYPE_P(to)) {
double f = RFLOAT_VALUE(to);
inf = isinf(f) && (signbit(f) ? desc : !desc);
}
else inf = 0;
if (FIXNUM_P(from) && (inf || FIXNUM_P(to)) && FIXNUM_P(step)) {
long i = FIX2LONG(from);
long diff = FIX2LONG(step);
if (inf) {
for (;; i += diff)
rb_yield(LONG2FIX(i));
}
else {
long end = FIX2LONG(to);
if (desc) {
for (; i >= end; i += diff)
rb_yield(LONG2FIX(i));
}
else {
for (; i <= end; i += diff)
rb_yield(LONG2FIX(i));
}
}
}
else if (!ruby_float_step(from, to, step, FALSE, FALSE)) {
VALUE i = from;
if (inf) {
for (;; i = rb_funcall(i, '+', 1, step))
rb_yield(i);
}
else {
ID cmp = desc ? '<' : '>';
for (; !RTEST(rb_funcall(i, cmp, 1, to)); i = rb_funcall(i, '+', 1, step))
rb_yield(i);
}
}
return from;
}
Generates a sequence of numbers; with a block given, traverses the sequence.
Of the Core and Standard Library classes, Integer, Float, and Rational use this implementation.
A quick example:
squares = [] 1.step(by: 2, to: 10) {|i| squares.push(i*i) } squares # => [1, 9, 25, 49, 81]
The generated sequence:
-
Begins with
self. -
Continues at intervals of
by(which may not be zero). -
Ends with the last number that is within or equal to
to; that is, less than or equal totoifbyis positive, greater than or equal totoifbyis negative. Iftoisnil, the sequence is of infinite length.
If a block is given, calls the block with each number in the sequence; returns self. If no block is given, returns an Enumerator::ArithmeticSequence.
Keyword Arguments
With keyword arguments by and to, their values (or defaults) determine the step and limit:
# Both keywords given. squares = [] 4.step(by: 2, to: 10) {|i| squares.push(i*i) } # => 4 squares # => [16, 36, 64, 100] cubes = [] 3.step(by: -1.5, to: -3) {|i| cubes.push(i*i*i) } # => 3 cubes # => [27.0, 3.375, 0.0, -3.375, -27.0] squares = [] 1.2.step(by: 0.2, to: 2.0) {|f| squares.push(f*f) } squares # => [1.44, 1.9599999999999997, 2.5600000000000005, 3.24, 4.0] squares = [] Rational(6/5).step(by: 0.2, to: 2.0) {|r| squares.push(r*r) } squares # => [1.0, 1.44, 1.9599999999999997, 2.5600000000000005, 3.24, 4.0] # Only keyword to given. squares = [] 4.step(to: 10) {|i| squares.push(i*i) } # => 4 squares # => [16, 25, 36, 49, 64, 81, 100] # Only by given. # Only keyword by given squares = [] 4.step(by:2) {|i| squares.push(i*i); break if i > 10 } squares # => [16, 36, 64, 100, 144] # No block given. e = 3.step(by: -1.5, to: -3) # => (3.step(by: -1.5, to: -3)) e.class # => Enumerator::ArithmeticSequence
Positional Arguments
With optional positional arguments to and by, their values (or defaults) determine the step and limit:
squares = [] 4.step(10, 2) {|i| squares.push(i*i) } # => 4 squares # => [16, 36, 64, 100] squares = [] 4.step(10) {|i| squares.push(i*i) } squares # => [16, 25, 36, 49, 64, 81, 100] squares = [] 4.step {|i| squares.push(i*i); break if i > 10 } # => nil squares # => [16, 25, 36, 49, 64, 81, 100, 121]
Implementation Notes
If all the arguments are integers, the loop operates using an integer counter.
If any of the arguments are floating point numbers, all are converted to floats, and the loop is executed floor(n + n*Float::EPSILON) + 1 times, where n = (limit - self)/step.