Decimal.from_float

Decimal.from_floatf mc explicit

Group: conversions

Documentation

Construct a Decimal from a Float.

Arguments

• f: The Float to construct a Decimal from.
• mc: The Math_Context to use to specify precision and Rounding_Mode. If a Math_Context is used, there is a possibility of a loss of precision.

Errors

• If a Text argument is incorrectly formatted, a Number_Parse_Error is thrown.
• If the construction of the Decimal results in a loss of precision, a Loss_Of_Numeric_Precision warning is attached. This can happen in the followoing ways:
  • A Float value is implicitly converted to a Decimal (either by calling Decimal.from or by passing the Float as a parameter of type Decimal)
  • A Math_Context value is explicitly passed, and the precision it specifies is not sufficient to precisely represent the argument to be converted
• If an arithmetic operation is used on mixed arguments (a Decimal and a Float), an Illegal_Argument error is thrown.
• If an arithmetic operation is used on a Decimal that was implicitly converted from a Float (either by calling Decimal.from or by passing the Float as a parameter of type Decimal), an Illegal_Argument error is thrown.
• If a floating-poing argument is NaN or +/- Inf, an Illegal_Argument error is thrown.

^ Example Create a Decimal from a Float.

c = 12.345.to_decimal

^ Example Create a Decimal from a Float.

c = dec 12.345

Remarks

Precision Loss

A Decimal can represent any Float precisely. However, some Float literals, such as 0.1, cannot be represented exactly to infinite precision by a Float. For this reason, constructing a Decimal from a Float always attaches a Loss_Of_Numeric_Precision warning to the result.

Creating Decimals and Converting to Decimal

When creating a Decimal from a literal floating-point value, the preferred method is to express the literal as a string and use Decimal.from_text, since this will give a Decimal that matches the value precisely.

To convert a Float or Integer to a Decimal, use its .to_decimal method.

You can also use the convenience method dec to convert any Integer, Float, or Text value to a Decimal. dec does not attach a warning.