examples/gallery/07-strings.hero

## Strings
#
# A `str` is immutable UTF-8, indexed in bytes. `s[i]` is an `i64` in
# 0..255, and `s.chars()` walks characters as one-character strings — the
# two are different jobs and the language refuses to blur them.

# Bytes, not characters: this counts the ASCII spaces.
function space_count(s: str) -> i64
    seen: i64 @= 0

    for i in range(from: 0, to: s.len())
        if s[i] == ' '
            seen @ seen + 1

    return seen

# Characters, not bytes: this one is right for text.
function letters_of(s: str) -> [str]
    out: [str] @= []

    for c in s.chars()
        if c != " "
            out @ out.push(c)

    return out

# Splitting on a single space, written out. There is no library to hide in.
function words_of(s: str) -> [str]
    out: [str] @= []
    start: i64 @= 0

    for i in range(from: 0, to: s.len())
        if s[i] == ' '
            if i > start
                out @ out.push(s.slice(from: start, to: i))
            start @ i + 1

    if s.len() > start
        out @ out.push(s.slice(from: start, to: s.len()))
    return out

# `join` is the other direction, and the separator is an argument, not a
# convention.
function sentence_of(words: [str]) -> str
    return words.join(" ")

function initials_of(words: [str]) -> str
    out: str @= ""

    for w in words
        if w.len() > 0
            out @ out + w.slice(from: 0, to: 1)

    return out

test "bytes, characters and words"
    assert space_count("a b c") == 2
    assert letters_of("a b").len() == 2
    assert words_of("one  two three").len() == 3
    assert sentence_of(["one", "two"]) == "one two"
    assert initials_of(["heroes", "language"]) == "hl"

function main()
    words = words_of("the quick brown fox")
    print(sentence_of(words))
    print(initials_of(words))