Text

Use this when concatenating, formatting, splitting, searching, or matching strings.

Core operations

Function	Signature	Description	Example
cat	t t > t	Concatenate two strings	cat "hello" " world" -> "hello world"
len	t > n	String length	len "hello" -> 5
trm	t > t	Trim whitespace	trm " hi " -> "hi"
spl	t t > L t	Split string by delimiter	spl "a,b,c" "," -> ["a","b","c"]
has	t t > b	Check if string contains substring	has "hello" "ell" -> true
idxof	t t > O n	First code-point index of substring, or nil. Empty needle returns 0 (Python/JS convention). Pair with slc for split-on-first-occurrence. (ILO-39, 26.5)	idxof "key=value" "=" -> 3

Regex

Function	Signature	Description	Example
rgx	t t > L t	Regex match (returns captures)	rgx "abc123" "[0-9]+" -> ["123"]
rgxall	t t > L (L t)	All matches with captures, one inner list per match. With no capture groups, each inner list holds the whole match.	rgxall "(\\w+)=(\\d+)" "a=1 b=2" -> [["a","1"],["b","2"]]
rgxall1	t t > L t	All matches of a single-group pattern, flattened. With no capture groups, returns the list of whole matches. Errors at verify-time if the pattern has 2+ capture groups, use rgxall instead.	rgxall1 "(\\d+)" "a=1 b=2" -> ["1","2"]
rgxall-multi	L t t > L t	Multi-pattern flat-match. Apply each pattern in the list to the string and concatenate hits in pattern order. Per-pattern semantics follow rgxall1 (0 groups -> whole matches; 1 group -> capture-1 strings; 2+ groups errors).	rgxall-multi ["\\d+" "[A-Z]+"] "x=1 ERR=2" -> ["1","2","ERR"]

Formatting

Function	Signature	Description	Example
fmt	t ... > t	Format string with values	fmt "{.2f} {:5}" 3.14159 42
fmt2	n n > t	Format a number to N decimal places (half-to-even rounding; digits clamped to 0..=20). Decimal formatter, not a list-splat variant of fmt. Compose with fmt for template + precision.	fmt2 3.14159 2 -> "3.14", fmt "x={}" (fmt2 v 2)

fmt is pure-functional sprintf, not print. A bare fmt "..." v statement is silently discarded on every engine. Use prnt fmt "..." v to print or line=fmt "..." v to capture. The verifier emits ILO-T032 when fmt/fmt2 is a non-tail statement with no binding (tail position, e.g. f v:n>t;fmt "x={}" v, is the documented “return formatted text” idiom and does not warn).

Supported placeholder specs:

Spec	Meaning	Example
{}	Any value	fmt "{}" 42 → "42"
{.Nf} / {:.Nf}	N decimal places	fmt "{.2f}" 3.14159 → "3.14"
{:N}	Right-align to width N	fmt "{:5}" "hi" → " hi"
{:Nd}	Integer, right-aligned to width N	fmt "{:5d}" 42.0 → " 42"
{:<N}	Left-align to width N	fmt "{:<5}" "hi" → "hi "

Zero-padded widths ({:06d}) and {:.N} without the f suffix are rejected at verify-time when the template is a literal, or at runtime otherwise.

Conversion

Function	Signature	Description	Example
str	_ > t	Convert any value to string	str 42 -> "42"
num	t|n > R n t	Polymorphic: parse text or identity-wrap a number as Ok. Saves the num (str x) roundtrip when x may already be numeric (e.g. from jpar! on a JSON number)	num "42" -> Ok 42, num 42 -> Ok 42

Output

Function	Signature	Description	Example
prnt	_ > _	Print value and return it	prnt "hello"

Aliases

Long form	Short form
concat	cat
length	len
trim	trm
split	spl
contains	has
format	fmt
regex	rgx
print	prnt