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description
Functions for manipulating decimal values with proper rounding. This should be used for modeling math on money amounts.

Copy of Decimals

(use-package 'decimal)

You must convert your numbers into decimal types using the helpers, and then use the decimal functions on these decimal types.

It makes heavy usage of the github.com/shopspring/decimal go package.

to-decimal

Coerce a decimal in string, number, or decimal format into a decimal type.

(to-decimal "1.22")
#<native value: decimal.Decimal>

decimal-string

Convert a decimal type into a string.

shiro> (decimal-string (to-decimal 1.22))
"1.22"

decimal-float

Convert a decimal type into a float.

shiro> (decimal-float (to-decimal "1.22"))
1.22

decimal+

Add var arg decimals. Arguments are coerced into a decimal type.

  (assert-string= "6.79" (decimal-string (decimal+ 1 4.56 1.23)))

decimal-

Subtract var arg decimals. Arguments are coerced into a decimal type.

  (assert-string= "3.33" (decimal-string (decimal- 4.56 1.23)))

decimal*

Multiply var arg decimals. Arguments are coerced into a decimal type.

  (assert-string= "24" (decimal-string (decimal* 2 3 4)))

decimal/

Divide var arg decimals. Arguments are coerced into a decimal type.

  (assert-string= "1" (decimal-string (decimal/ 4 2 2)))

decimal=

Check equality of two decimals. Arguments are coerced into a decimal type.

  (assert (decimal= 2 (decimal- 5.00 3)))

decimal<

Check less than of two decimals. Arguments are coerced into a decimal type.

  (assert (decimal< 2 5))

decimal<=

Check less than or equal of two decimals. Arguments are coerced into a decimal type.

  (assert (decimal<= 2 5))

decimal>

Check greater than of two decimals. Arguments are coerced into a decimal type.

  (assert (decimal> 5 2))

decimal>=

Check greater than or equal of two decimals. Arguments are coerced into a decimal type.

  (assert (decimal>= 5 2))

decimal-pow

Raise a decimal to a power. Arguments are coerced into a decimal type.

  (assert-string= "25" (decimal-string (decimal-pow 5 2))))

decimal-floor

Compute the floor of a decimal. Arguments are coerced into a decimal type.

  (assert-string= "2" (decimal-string (decimal-floor 2.99))))

decimal-ceil

Compute the ceiling of a decimal. Arguments are coerced into a decimal type.

  (assert-string= "3" (decimal-string (decimal-ceil 2.99))))

decimal-abs

Compute the absolute value of a decimal. Arguments are coerced into a decimal type.

  (assert-string= "2.99" (decimal-string (decimal-abs -2.99)))

decimal-sign

Get the sign (-1, 0, 1) of a decimal. Arguments are coerced into a decimal type.

  (assert (= -1 (decimal-sign -2)))

decimal-round

Round a decimal. Several rounding modes are supported (see shopspring repo for more details). Arguments are coerced into a decimal type.

  (assert-string= "1.23" (decimal-string "1.23"))
  (assert-string= "1.3" (decimal-string "1.29" :places 1))
  (assert-string= "1.3" (decimal-string "1.29" :places 1 :rounding 'fixed))
  (assert-string= "1.29" (decimal-string "1.299" :places 2 :rounding 'truncate))
  (assert-string= "1.2" (decimal-string "1.23" :places 1 :rounding 'bank))