Documentation

The value of a plain scalar without a tag. Not every such scalar is a string, e.g. null, true, 12, 0x1F and 1.5e3 are not. Quoted and block scalars are always strings.

A float whose exponent in scientific notation is beyond the range from -1000 to 1000, e.g. 1e1001, 10e1000 or 1e-1001, becomes infinity or zero, as a double does. The decoders reject such a number, because its value is not exact.

>>> map resolvePlain ["", "true", "0x1F", "1.5e3", ".inf", "yes", "9.10.3"]
[Null,Bool True,Int 31,Float (Finite 1500.0),Float Infinity,String "yes",String "9.10.3"]

The value of a scalar with the given resolved tag, e.g. tag:yaml.org,2002:int. Return Nothing if the text is not valid for a tag of the core schema. A scalar with another tag is a string.

A float beyond the limit becomes infinity or zero, as in resolvePlain.

>>> [resolveTagged floatTag "1", resolveTagged intTag "abc", resolveTagged seqTag "x", resolveTagged "!point" "1"]
[Just (Float (Finite 1.0)),Nothing,Nothing,Just (String "1")]

The value of a plain scalar, Left if the value is not exact.

The value of a scalar with a tag, Left if the value is not exact.

A plain scalar that starts with the character can be a number. Only such a scalar can have a value that is not exact.

A plain scalar with the text is a string, e.g. 9.10.3 is a string, but 9.10 and true are not. The check ignores the syntax, so e.g. a: b passes. For both checks, use isPlainSafe.

>>> map isPlainString ["9.10.3", "9.10", "true", "a: b"]
[True,False,False,True]

The string reads back as the same string if it is a plain scalar in the block style, as a value or as a key. A key without ? must also have at most 1024 characters, which the check does not count. In a flow collection the characters ,[]{} need quotes too, so the check does not apply there.

>>> map isPlainSafe ["a:b", "a: b", "- a", "a #b", "9.10"]
[True,False,False,False,False]

As isPlainSafe, and common YAML 1.1 parsers also read the plain scalar as a string, e.g. not yes as a boolean or 12:30 as a number. The encoder writes a string without quotes only if it passes this check.

>>> map isPlainPortable ["a:b", "yes", "12:30", "2024-01-01", "9.10.3"]
[True,False,False,False,True]

A word that YAML 1.1 reads as a boolean, but YAML 1.2 as a string, e.g. yes or off.

A common YAML 1.1 parser reads a plain scalar with the text as a value that is not a string, e.g. the boolean yes, the base-60 number 12:30 or the date 2024-01-01. The patterns cover what PyYAML, Ruby's Psych and go-yaml v2, which Kubernetes uses, accept. The YAML 1.1 types themselves are not enough: the parsers accept more, e.g. 1,000 in Psych and 0X1F in go-yaml v2, and the type of floats accepts too much, e.g. 1.2.3.

A common YAML 1.1 parser reads a plain scalar with the text as a timestamp and can build it. PyYAML has the years from 1 to 9999 of Python, and it rejects the hour 24, a leap second and a time zone of 24 hours. Psych reads the hour 24 and a leap second as a later time.

>>> map isYaml11Timestamp ["2024-01-01", "2024-01-01T12:30:00Z", "0000-01-01", "2016-12-31T23:59:60Z", "12:30"]
[True,True,False,False,False]

The error for a number beyond maxExponent.