instance method Float#prev_float

prev_float -> Float[permalink][rdoc]

浮動小数点数で表現可能な self の前の値を返します。

(-Float::MAX).prev_float と (-Float::INFINITY).prev_float は -Float::INFINITY を返します。Float::NAN.prev_float は Float::NAN を返します。

例

p 0.01.prev_float  # => 0.009999999999999998
p 1.0.prev_float   # => 0.9999999999999999
p 100.0.prev_float # => 99.99999999999999

p 0.01 - 0.01.prev_float   # => 1.734723475976807e-18
p 1.0 - 1.0.prev_float     # => 1.1102230246251565e-16
p 100.0 - 100.0.prev_float # => 1.4210854715202004e-14

f = 0.01; 20.times { printf "%-20a %s\n", f, f.to_s; f = f.prev_float }
# => 0x1.47ae147ae147bp-7 0.01
#    0x1.47ae147ae147ap-7 0.009999999999999998
#    0x1.47ae147ae1479p-7 0.009999999999999997
#    0x1.47ae147ae1478p-7 0.009999999999999995
#    0x1.47ae147ae1477p-7 0.009999999999999993
#    0x1.47ae147ae1476p-7 0.009999999999999992
#    0x1.47ae147ae1475p-7 0.00999999999999999
#    0x1.47ae147ae1474p-7 0.009999999999999988
#    0x1.47ae147ae1473p-7 0.009999999999999986
#    0x1.47ae147ae1472p-7 0.009999999999999985
#    0x1.47ae147ae1471p-7 0.009999999999999983
#    0x1.47ae147ae147p-7  0.009999999999999981
#    0x1.47ae147ae146fp-7 0.00999999999999998
#    0x1.47ae147ae146ep-7 0.009999999999999978
#    0x1.47ae147ae146dp-7 0.009999999999999976
#    0x1.47ae147ae146cp-7 0.009999999999999974
#    0x1.47ae147ae146bp-7 0.009999999999999972
#    0x1.47ae147ae146ap-7 0.00999999999999997
#    0x1.47ae147ae1469p-7 0.009999999999999969
#    0x1.47ae147ae1468p-7 0.009999999999999967

[SEE_ALSO] Float#next_float