Strings

Auto-generated from src/stdlib/strings.mcrs — do not edit manually.

API

• str_len
• str_concat
• str_contains
• str_slice

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str_len v1.0.0

Returns the length of the string stored at rs:strings.{s}.

LIMITATION (MC 1.21.4): execute store result score ... run data get storage returns 1 for any plain string NBT tag, not the character count. To get a true character count, the string must be stored as an NBT list of single-char strings (e.g. ["h","e","l","l","o"]), in which case data_get returns the list length correctly.

For literal strings whose length is known at compile time, prefer using the constant directly — the compiler will fold it.

fn str_len(s: string) -> int

Parameters

Parameter	Description
s	NBT field name in rs:strings (e.g. "A")

Returns: 1 for plain string tags; list element count for char-list strings.

Example

str_len("A")  // result: 1 (plain string) or char count (char-list)

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str_concat v1.0.0

Concatenates two strings from rs:strings and writes the result to rs:strings.Result as an NBT list [a_value, b_value].

The result list is suitable for use in tellraw JSON text components: tellraw @a

LIMITATION (MC 1.21.4): MC has no native string concatenation command. Single-string concatenation (e.g. "ab" from "a"+"b") requires a recursive macro helper function; this is out of scope for a pure stdlib. The NBT list representation works for display (tellraw) but cannot be passed back to further string operations without conversion.

ALTERNATIVE for display: use a tellraw JSON array directly: tellraw @a [{"storage":"rs:strings","nbt":"A"},{"storage":"rs:strings","nbt":"B"}]

fn str_concat(a: string, b: string)

Parameters

Parameter	Description
a	NBT field name of the first string in rs:strings (e.g. "A")
b	NBT field name of the second string in rs:strings (e.g. "B")

Returns: rs:strings.Result is set to an NBT list [valueA, valueB]

Example

str_concat("A", "B")  // rs:strings.Result = ["hello", "world"]

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str_contains v1.0.0

Checks whether the string at rs:strings.{s} contains the substring at rs:strings.{sub}. Returns 1 if found, 0 if not found.

NOT FEASIBLE (MC 1.21.4): Minecraft datapacks do not provide a native substring search command. There is no execute if data form that tests whether one string is contained within another.

THIS FUNCTION ALWAYS RETURNS 0.

WORKAROUNDS for datapack authors:

1. If sub is a compile-time constant and the check position is known, use str_slice to extract a window and compare via scoreboard.
2. Pre-process strings server-side and store a presence flag in NBT.
3. Use a macro function (MC 1.20.2+) that iterates over character positions with $(var) substitution and returns early on match.

fn str_contains(s: string, sub: string) -> int

Parameters

Parameter	Description
s	NBT field name of the haystack string in rs:strings
sub	NBT field name of the needle string in rs:strings

Returns: 0 (always — not implemented due to MC limitation)

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str_slice v2.2.0

Extracts a substring from rs:strings.{s} and writes it to rs:strings.Result. Uses the MC 1.20.2+ data modify ... set string ... start end feature.

Indices follow Java/Python slicing semantics:

• start is inclusive, 0-based.
• end is exclusive (end = start + length).
• Negative end counts from the end of the string (e.g. -1 = all but last char).
• Omitting end (use a very large positive int like 999999) copies to end of string.

Examples: str_slice("A", 0, 5) → first 5 characters of rs:strings.A str_slice("A", 2, -1) → all but first 2 and last 1 characters

fn str_slice(s: string, start: int, end: int)

Parameters

Parameter	Description
s	NBT field name of the source string in rs:strings (e.g. "A")
start	Start index (inclusive, 0-based)
end	End index (exclusive); negative counts from string end

Returns: rs:strings.Result contains the extracted substring

Example

str_slice("A", 0, 5)   // first 5 chars of rs:strings.A
str_slice("A", 2, -1)  // drop first 2 and last 1 chars

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