Numeric#step

Tadayoshi_F · July 17, 2006, 2:46pm

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$ ruby -v -eInf=1.0/0 -e’1.step(Inf, Inf){|x| p x}’
ruby 1.8.4 (2005-12-24) [i386-freebsd5.4]

$ ruby -v -r bigdecimal -r bigdecimal/util -eInf=1.0/0
-e"‘1’.to_d.step(Inf, Inf){|x| p x}"
ruby 1.8.4 (2005-12-24) [i386-freebsd5.4]

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$ ruby -v -r bigdecimal -r bigdecimal/util -eInf=1.0/0
-e"‘1’.to_d.step(Inf.to_d, Inf.to_d){|x| p x}"

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$ ruby -v -eInf=1.0/0 -e’10.step(1, Inf){|x| p x}’
ruby 1.8.4 (2005-12-24) [i386-freebsd5.4]
NaN

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$ ruby -v -r bigdecimal -r bigdecimal/util -eInf=1.0/0
-e"‘10’.to_d.step(1, Inf.to_d){|x| p x}"
ruby 1.8.4 (2005-12-24) [i386-freebsd5.4]

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Tadayoshi_F · July 18, 2006, 3:12pm

|From: Tadayoshi F. [email protected]
|Date: Mon, 17 Jul 2006 21:44:58 +0900

Numeric#step e$B$G$9$,!“e(B1.0/0 = e$BL58BBg$G$”$k$H$-!"e(B

$ ruby -v -eInf=1.0/0 -e’1.step(Inf, Inf){|x| p x}’
ruby 1.8.4 (2005-12-24) [i386-freebsd5.4]

$ ruby -v -eInf=1.0/0 -e’10.step(1, Inf){|x| p x}’
ruby 1.8.4 (2005-12-24) [i386-freebsd5.4]
NaN

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— numeric.c~ 2006-05-01 12:46:46 +0900
+++ numeric.c 2006-07-18 21:05:38 +0900
@@ -1478,22 +1478,38 @@
else if (TYPE(from) == T_FLOAT || TYPE(to) == T_FLOAT || TYPE(step)
== T_FLOAT) {
const double epsilon = DBL_EPSILON;
double beg = NUM2DBL(from);
double end = NUM2DBL(to);
double unit = NUM2DBL(step);
double n = (end - beg)/unit;
double err = (fabs(beg) + fabs(end) + fabs(end-beg)) / fabs(unit) *
epsilon;
long i;

int warn = 0;
if (isinf(beg) || isinf(unit)) {

  if ((unit>0 && (end-beg)>=0) || (unit<0 && (end-beg)<=0)) {

```
      unit = 0;
```
```
      n = 0;
```
```
  } else {
```
```
      n = -1;
```
```
  }
```
```
  err = 0;
```
}
if (err>0.5) err=0.5;
n = floor(n + err) + 1;
if (n>LONG_MAX) {
```
  n = LONG_MAX;
```
```
  warn = 1;
```
}
for (i=0; i<n; i++) {
rb_yield(rb_float_new(i*unit+beg));
}
if (warn)
```
  rb_warn("iteration is reduced to LONG_MAX times");
```
}
else {
VALUE i = from;
ID cmp;

if (RTEST(rb_funcall(step, ‘>’, 1, INT2FIX(0)))) {
cmp = ‘>’;
}

ChangeLog
- numeric.c (num_step): cares for Infifnity cases.
  repeats at most LONG_MAX times in Float cases.
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$ ./ruby -v
ruby 1.8.5 (2006-07-18) [i686-linux]
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,1){|x| p x; break if x.abs>5}’
1.0
2.0
3.0
4.0
5.0
6.0
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,-1){|x| p x; break if x.abs>5}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,1){|x| p x; break if x.abs>5}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,-1){|x| p x; break if x.abs>5}’
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
$ ./ruby -e’Inf=1.0/0;i=0; Inf.step(1,-1){|x| p x; break if (i+=1)>5}’
Infinity
Infinity
Infinity
Infinity
Infinity
Infinity
$ ./ruby -e’Inf=1.0/0;i=0; Inf.step(1,1){|x| p x; break if (i+=1)>5}’
$ ./ruby -e’Inf=1.0/0;i=0; (-Inf).step(1,-1){|x| p x; break if
(i+=1)>5}’
$ ./ruby -e’Inf=1.0/0;i=0; (-Inf).step(1,1){|x| p x; break if (i+=1)>5}’
-Infinity
-Infinity
-Infinity
-Infinity
-Infinity
-Infinity
$ ./ruby -e’Inf=1.0/0; 1.step(10,Inf){|x| p x}’
NaN
$ ./ruby -e’Inf=1.0/0; 1.step(-10,Inf){|x| p x}’
NaN
$ ./ruby -e’Inf=1.0/0; 1.step(10,-Inf){|x| p x}’
NaN
$ ./ruby -e’Inf=1.0/0; 1.step(-10,-Inf){|x| p x}’
NaN
$ ./ruby -e’Inf=1.0/0; 1.step(1,Inf){|x| p x}’
NaN
$ ./ruby -e’Inf=1.0/0; 1.step(1,-Inf){|x| p x}’
NaN
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,-Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,-Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(-Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(Inf,-Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(-Inf,-Inf){|x| p x}’

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$ ./ruby -e’Inf=1.0/0; 1.step(Inf,1){|x| p x; break if x.abs>5}‘1.0
2.0
3.0
4.0
5.0
6.0
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,-1){|x| p x; break if x.abs>5}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,1){|x| p x; break if x.abs>5}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,-1){|x| p x; break if x.abs>5}’
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
$ ./ruby -e’Inf=1.0/0;i=0; Inf.step(1,-1){|x| p x; break if (i+=1)>5}’
Infinity
$ ./ruby -e’Inf=1.0/0;i=0; Inf.step(1,1){|x| p x; break if (i+=1)>5}’
$ ./ruby -e’Inf=1.0/0;i=0; (-Inf).step(1,-1){|x| p x; break if
(i+=1)>5}’
$ ./ruby -e’Inf=1.0/0;i=0; (-Inf).step(1,1){|x| p x; break if (i+=1)>5}’
-Infinity
$ ./ruby -e’Inf=1.0/0; 1.step(10,Inf){|x| p x}’
1.0
$ ./ruby -e’Inf=1.0/0; 1.step(-10,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(10,-Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(-10,-Inf){|x| p x}’
1.0
$ ./ruby -e’Inf=1.0/0; 1.step(1,Inf){|x| p x}’
1.0
$ ./ruby -e’Inf=1.0/0; 1.step(1,-Inf){|x| p x}’
1.0
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,Inf){|x| p x}’
1.0
$ ./ruby -e’Inf=1.0/0; 1.step(Inf,-Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; 1.step(-Inf,-Inf){|x| p x}’
1.0
$ ./ruby -e’Inf=1.0/0; Inf.step(Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(-Inf,Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(Inf,-Inf){|x| p x}’
$ ./ruby -e’Inf=1.0/0; Inf.step(-Inf,-Inf){|x| p x}’
Infinity