ruby.md

title	description
Floating-point cheat sheet for Ruby	Tips for using floating-point and decimal numbers in Ruby

Floating-Point Types

Ruby floats are mapped to double-precision IEEE 754.

	f = 0.1 

Decimal Types

Ruby has an arbitrary-precision decimal type named BigDecimal in the bigdecimal module, which also allows to choose the rounding mode.

	require 'bigdecimal'

	a = BigDecimal('0.1')
	b = BigDecimal('0.2')
	c = a + b # returns a BigDecimal representing exactly 0.3

How to Round

To get a string:

	"%.2f" % 1.2399 # returns "1.24"
	"%.3f" % 1.2399 # returns "1.240"
	"%.2f" % 1.2 # returns "1.20"

To print to standard output:

	puts "%.2f" % 1.2399

Resources

• Floating Point Arithmetic
• The bigdecimal module
• String formatting in Ruby

---

title: 为 Ruby 准备的浮点小抄 description: Tips for using floating-point and decimal numbers in Ruby

浮点类型

Ruby 浮点映射 IEEE 754 双精度浮点.

	f = 0.1 

小数类型

在 Ruby 的 bigdecimal 模块中有一个称为 BigDecimal 的 arbitrary-precision 小数类型，它同时允许选择 取整模式。

	require 'bigdecimal'

	a = BigDecimal('0.1')
	b = BigDecimal('0.2')
	c = a + b # 返回 BigDecimal 表示的精确的 0.3

如何取整

得到字符串：

	"%.2f" % 1.2399 # 返回 "1.24"
	"%.3f" % 1.2399 # 返回 "1.240"
	"%.2f" % 1.2 # 返回 "1.20"

打印到标准输出：

	puts "%.2f" % 1.2399

资源

• 浮点代数
• bigdecimal 模块
• 在 Ruby 里进行字符串格式化