[m-shichida]

Background

The function descriptions in lib/xls_function/locales/*.yml were mostly based on Microsoft Excel's documentation.
Some of them did not match how this library actually behaves, so users could not rely on them.

Changes

• Rewrote every description in ja.yml based on the implementation in lib/xls_function/evaluators/functions/.
• Updated en.yml as a translation of the new ja.yml, so both locales describe the same behavior.
• Only the descriptions text changed. No code changes, and no keys were added or removed (57 descriptions in each file). errors is unchanged.

Examples of descriptions that now match the actual behavior:

Function	Previous description	Actual behavior (now documented)
DBCS	Converts half-width letters to full-width	Only uppercase letters, digits, and katakana are converted
LEFT / RIGHT	num_chars is optional	Omitting num_chars returns #VALUE!
AND / OR	(not mentioned)	Arguments are evaluated left to right and stop once the result is decided
IFS	(not mentioned)	Returns empty (nil) when no condition is TRUE
SWITCH	Unclear signature	Returns #N/A when nothing matches and no default is given
ISNUMBER	(not mentioned)	A string of digits such as "123" returns FALSE
CHAR	Any number	Use 0-127 (ASCII). Use UNICHAR for other characters

How to verify

Anyone can check the behavior described above in bin/console:

XlsFunction.evaluate('DBCS("abcABC123")')     # => "abcＡＢＣ１２３"
XlsFunction.evaluate('LEFT("abc")')           # => "#VALUE!"
XlsFunction.evaluate('AND(FALSE, 1/0)')       # => false (1/0 is not evaluated)
XlsFunction.evaluate('IFS(FALSE, 1)')         # => nil
XlsFunction.evaluate('SWITCH(3, 1, "a", 2, "b")') # => "#N/A"
XlsFunction.evaluate('ISNUMBER("123")')       # => false
XlsFunction.evaluate('EDATE("2026/1/31", 1)') # => 0.4608e5 (serial number of 2026/2/28)

To see the descriptions in each locale:

I18n.locale = :en
XlsFunction.functions['DBCS'][:description]
# => "DBCS(text) Converts half-width uppercase letters, digits, and katakana to full-width."

I18n.locale = :ja
XlsFunction.functions['DBCS'][:description]
# => "DBCS(文字列) 半角の英大文字・数字・カタカナを全角に変換します。"

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