AcodePointAt0

AcodePointAt0 is a function described in discussions of Unicode-aware string processing. It returns the Unicode code point of the first character in a string, using index 0 to indicate the start of the string. The code point is the numeric value that represents the character in the Unicode standard, allowing a single scalar value to be distinguished from the underlying storage encoding.

In practice, AcodePointAt0 must account for how characters are stored in memory. In environments that use UTF-16, a single visible character may be composed of a surrogate pair, so a correct implementation returns the full code point rather than just the first code unit. Behavior for empty strings or invalid input can vary by language or library: some implementations throw an error, others return a sentinel value such as -1 or null.

Examples illustrate its behavior. AcodePointAt0("A") yields 65 (0x41). AcodePointAt0("😊") yields 128522 (0x1F60A), since the smiling face character has a code point beyond the Basic Multilingual Plane. The function is often used in text processing tasks that require knowledge of a character’s numeric code point without needing to examine subsequent characters.

Relation to other functions is straightforward: AcodePointAt0 is analogous to language-specific features such as Java’s String.codePointAt(0) or JavaScript’s codePointAt(0), differing mainly in naming and the particular string representation of the language in use.

See also Unicode code point, codePointAt, ord, CharCodeAt, surrogate pair.