5.1.7. Strings

This tutorial covers string literals, escape sequences, string interpolation, character access, slicing, type conversions, case conversion, searching, padding, trimming, formatted output, and utilities from the strings and daslib/strings_boost modules.

5.1.7.1. String literals

String literals are enclosed in double quotes. Standard escape sequences are supported:

print("tab:\there\n")
print("newline:\nhere\n")
print("backslash: \\\n")
print("quote: \"\n")

5.1.7.2. String interpolation

Expressions inside { } are evaluated and inserted:

let name = "daslang"
let version = 0.6
print("{name} version {version}\n")

5.1.7.3. Length and character access

length returns the number of bytes. character_at returns the integer character code at a given index. Convert back with to_char:

let text = "Hello"
print("{length(text)}\n")     // 5

let ch = character_at(text, 0)
print("{ch}\n")               // 72  (ASCII for 'H')
print("{to_char(ch)}\n")      // H

5.1.7.4. Slicing

slice extracts a substring by start and end indices:

let phrase = "Hello, World!"
print("{slice(phrase, 0, 5)}\n")   // Hello
print("{slice(phrase, 7)}\n")      // World!

5.1.7.5. Comparison

Strings support the usual comparison operators:

"abc" == "abc"   // true
"abc" < "xyz"    // true

Use compare_ignore_case for case-insensitive comparison. It returns 0 when strings are equal ignoring case:

compare_ignore_case("Hello", "hello")   // 0 (equal)
compare_ignore_case("abc", "XYZ")       // negative (a < X)

5.1.7.6. Case conversion

to_upper and to_lower create new strings with changed case. capitalize uppercases the first character and lowercases the rest:

to_upper("hello")              // "HELLO"
to_lower("WORLD")              // "world"
capitalize("hello world")      // "Hello world"

5.1.7.7. Converting to and from strings

string(value) converts numeric types to a string. For booleans, use string interpolation:

let numStr = string(42)      // "42"
let fltStr = string(3.14)    // "3.14"

// For booleans, use interpolation:
let flag = true
print("{flag}\n")            // true

To convert strings to numbers, require strings and use to_int / to_float:

require strings

let n = to_int("123")       // 123
let f = to_float("3.14")    // 3.14

Note: int("123") does not work — you must use to_int.

5.1.7.8. Searching strings

find returns the index of the first occurrence, or -1 if not found. contains (from daslib/strings_boost) returns a boolean. count counts non-overlapping occurrences. last_index_of finds the last occurrence:

let sentence = "the quick brown fox"
find(sentence, "quick")            // 4
find(sentence, "slow")             // -1

contains(sentence, "quick")        // true
contains(sentence, "slow")         // false

count("abcabcabc", "abc")          // 3

last_index_of("one/two/three", "/")  // 7

5.1.7.9. Prefix, suffix, and trimming

starts_with and ends_with test for prefixes and suffixes. trim_prefix and trim_suffix remove them if present. strip removes leading and trailing whitespace:

starts_with("image.png", "image")           // true
ends_with("image.png", ".png")              // true

trim_prefix("Hello World", "Hello ")        // "World"
trim_suffix("file.txt", ".txt")             // "file"
trim_suffix("file.txt", ".png")             // "file.txt" (unchanged)

strip("  hello  ")                          // "hello"

is_null_or_whitespace checks if a string is empty or contains only whitespace:

is_null_or_whitespace("")     // true
is_null_or_whitespace("  ")   // true
is_null_or_whitespace("hi")   // false

5.1.7.10. Padding

pad_left and pad_right pad a string to a minimum width with a fill character (default is space):

pad_left("42", 6)          // "    42"
pad_left("42", 6, '0')    // "000042"
pad_right("hi", 6)        // "hi    "
pad_right("hi", 6, '.')   // "hi...."

5.1.7.11. Join and split

join concatenates an array of strings with a separator. split splits a string by a delimiter:

let parts = fixed_array("one", "two", "three")
join(parts, ", ")                    // "one, two, three"

var items <- split("apple,banana,cherry", ",")
// ["apple", "banana", "cherry"]

replace("aabbcc", "bb", "XX")       // "aaXXcc"

5.1.7.12. Formatted output with fmt

fmt uses {fmt}-library style format specifiers (not printf-style). It returns a formatted string:

fmt(":d", 42)          // "42"
fmt(":05d", 7)         // "00007"
fmt(":x", 255)         // "ff"
fmt(":.2f", 3.14159)   // "3.14"

5.1.7.13. Building strings

build_string constructs strings efficiently using a writer:

let result = build_string() $(var writer) {
    write(writer, "Name: ")
    write(writer, "Alice")
    write(writer, ", Score: ")
    write(writer, string(100))
}
print("{result}\n")   // "Name: Alice, Score: 100"

5.1.7.14. Running the tutorial

daslang.exe tutorials/language/07_strings.das