T Programming Language - string_manipulation

String Manipulation in T

This guide explains how string manipulation functions are named in T, when the str_ prefix is used, and which related helpers intentionally keep their original names.

The Basic Rule

String transformation and formatting functions in T use the str_ prefix.

This makes it easier to distinguish them from:

generic helpers in other packages,
functions that have non-string behavior,
selection helpers used in data manipulation.

Examples:

str_nchar("hello")          -- 5
str_substring("hello", 1, 4) -- "ell"
str_replace("banana", "a", "o") -- "bonono"
str_trim("  hello  ")       -- "hello"
str_join(["a", "b", "c"], "-") -- "a-b-c"
str_string(42)               -- "42"
str_split("a,b,c", ",")    -- ["a", "b", "c"]

Functions That Use `str_`

The shorter string-focused helpers follow this naming convention:

str_nchar()
str_substring()
str_replace()
str_trim()
str_lines()
str_words()
str_sprintf()
str_join()
str_string()
str_split()

The strsplit() name was normalized to str_split() to match the rest of the string API.

Why Some Names Stay Unchanged

Not every string-related helper is renamed.

Some functions deliberately keep their original names because they are already descriptive, are shared with another subsystem, or would become awkward if prefixed.

Examples that remain unchanged include:

contains()
starts_with()
ends_with()
replace_first()
trim_start()
trim_end()
char_at()
index_of()
last_index_of()
to_lower()
to_upper()
is_empty()
slice()

In particular, contains(), starts_with(), and ends_with() are also used as column-selection helpers in colcraft, so keeping those names makes the data-manipulation API more consistent.

Common Patterns

Inspecting strings

str_nchar("hello")
is_empty("")
contains("tlang", "lang")
starts_with("prefix", "pre")
ends_with("suffix", "fix")

Extracting and modifying text

str_substring("abcdef", 1, 4)
char_at("abcdef", 2)
str_replace("banana", "a", "o")
replace_first("banana", "a", "o")

Cleaning and splitting text

str_trim("  hello  ")
trim_start("  hello  ")
trim_end("  hello  ")
str_lines("a\nb\nc")
str_words("hello   world")
str_split("a,b,c", ",")

Formatting and conversion

str_sprintf("Hello, %s!", "world")
str_join(["red", "green", "blue"], ", ")
str_string(3.14)

Selection Helpers vs String Helpers

When working with DataFrames, some names such as starts_with() and contains() can be used for column selection:

df |> select(starts_with("petal"))
df |> select(contains("width"))

When called with string arguments, the same names still behave as string predicates:

starts_with("petal_width", "petal")
contains("petal_width", "width")

That is why these names are intentionally left without the str_ prefix.

For per-function details, see the reference pages: