Crate strp

Utility library for parsing data from an input string, or stdin if built with the std feature. Supports no_std contexts when built without the std feature enabled. Requires the alloc crate. The std feature is enabled by default.

Supports parsing one or multiple values from a string. Can parse primitives, Strings, or any type which derives the TryParse trait.

Supports parsing primitives from hexadecimal or binary values.

The try_parse, parse, try_scan and scan macros put high emphasis on deducing types, meaning you rarely need to specify the type yourself unless you want to enforce a specific type, or there’s missing context.

Basic parse and try_parse usage

parse and try_parse parses a single value from the source string, and has more cohesive errors than scan and try_scan.

// Attempts to parse  a number from `source` using `try_parse`
let source = String::from("number: 30");
let number = try_parse!(source => "number: {}");
assert_eq!(number, Ok(30));

// Internally calls `try_parse` and unwraps the result.
let source = "hello, world!";
let value: String = parse!(source => "hello, {}!");
assert_eq!(value, "world".to_string());

Neither parse or try_parse accepts anything other than one parsed value at a time. The following code will not compile.

let source = "some source"
let ok = parse!(source => "{}"); // Ok!

let err = parse!(source => "{} {}"); // Error! Attempting to parse multiple values with `parse`.

let err = parse!(source => "some source"); // Error! Attempting to parse no values using `parse`.

Basic scan and try_scan usage

scan and try_scan has less cohesive erros than parse and try_parse, but allows parsing multiple values from a single source string.

// Example of parsing 4 strings from one source string using `try_scan`
let source = String::from("this is four words!");
let matched = try_scan!(source => "{} {} {} {}!");
assert_eq!(
    matched,
    Ok((
        "this".to_string(),
         "is".to_string(),
         "four".to_string(),
         "words".to_string()
    ))
);

// Interally calls `try_scan` and unwraps the result.
let source = "add 20, 30";
let (left, right): (u32, u32) = scan!(source => "add {}, {}");
assert_eq!(left + right, 50);

Both scan or try_scan requires two or more parsed values at a time. The following code will not compile.

let source = "some source";
let ok = scan!(source => "{} {}"); // Ok!

let err = scan!(source => "{}"); // Error! Attempting to parse a single value with `scan`.

let err = scan!(source => "some source"); // Error! Attempting to parse no values using `scan`.

Using stdin with the std feature.

// Uses stdin as a source string.
let name: String = parse!("hello! my name is {}.");
println!("hello, {name}!");

let try_parse: Result<String, _> = try_parse!("Please, enter your name: {}.");
match try_parse {
    Ok(name) => println!("Thank you for inputing your name, {name}!"),
    Err(_) => println!("No name was given."),
}

// You can also use stdin for `scan` and `try_scan`
let (a, b, c): (u32, u32, u32) = scan!("{} + {} = {}");
assert_eq!(a + b, c);

let try_scan: Result<(u32, u32, u32), _> = try_scan!("{} + {} = {}");
match try_scan {
    Ok((a,b,c)) => println!("{a} + {b} = {c}"),
    Err(e) => println!("an erro occured: {e:?}"),
}

Inlining matched values.

let mut number = -1;
try_parse!("input number: 20" => "input number: {number}");
assert_eq!(number, 20);

let (mut l, mut r) = ("".to_string(), "".to_string());
try_scan!("hello world!" => "{l} {r}").expect("failed to parse");
assert_eq!((l, r), ("hello".to_string(), "world!".to_string()));

// If the parsing failed, an error is returned by the macro call.
let mut number: i32 = -1;
match try_parse!("fail 20" => "success {number}"){
    Ok(_) => println!("parsed value: {number}"),
    Err(_) => println!("failed to parse input string"),
}

// Inlining can also be paired with returning values in `scan` and `try_scan`.
let (mut left, mut right) = ("".to_string(), "".to_string());
let middle = scan!("left middle right" => "{left} {} {right}");
assert_eq!(
    (left, middle, right),
    ("left".to_string(), "middle".to_string(), "right".to_string())
);

// `scan` and `try_scan` can mix both inlining matching values,
// or alternatively capture them as a return value.
let (mut x, mut y, mut z) = (0, 0, 0);
let v = try_scan!("10, 20, 30, 40" => "{}, {x}, {y}, {z}");
assert_eq!((v, x, y, z), (Ok(10), 20, 30, 40));

let (mut x, mut y, mut z) = (0, 0, 0);
let v = try_scan!("10, 20, 30, 40" => "{x}, {}, {y}, {z}");
assert_eq!((v, x, y, z), (Ok(20), 10, 30, 40));

let (mut x, mut y, mut z) = (0, 0, 0);
let v = try_scan!("10, 20, 30, 40" => "{x}, {y}, {}, {z}");
assert_eq!((v, x, y, z), (Ok(30), 10, 20, 40));

let (mut x, mut y, mut z) = (0, 0, 0);
let v = try_scan!("10, 20, 30, 40" => "{x}, {y}, {z}, {}");
assert_eq!((v, x, y, z), (Ok(40), 10, 20, 30));

let (mut x, mut y) = (0, 0);
let v = try_scan!("10, 10, 20, 20" => "{x}, {}, {y}, {}");
assert_eq!(v, Ok((x,y)));

Hexadecimal and binary parsing.

// Need to specify 'u64' here, since otherwise the value will be too large.
let hex: Result<u64, _> =  
    try_parse!("input hex: 0x0123456789ABCDEF" => "input hex: 0x{:x}");
assert_eq!(hex, Ok(0x0123456789ABCDEF));

let bin: Result<u32, _> = try_parse!("input bin: 0b11110001" => "input bin: 0b{:b}");
assert_eq!(bin, Ok(0b11110001));

let (bin, hex) = scan!("bin: 0b101, hex: 0xFE" => "bin: 0b{:b}, hex: 0x{:x}");
assert_eq!((bin, hex), (0b101u32, 0xFEu32));

// Parsing as hexadecimal or binary also works with inlining.
let mut bin = -1;
parse!("binary value: 101" => "binary value: {bin:b}");
assert_eq!(bin, 0b101);

let (mut bin, mut hex) = (-1, -1);
scan!("bin: 1111, hex: F" => "bin: {bin:b}, hex: {hex:x}");
assert_eq!((bin, hex), (0b1111, 0xF));

Macros

parse

Interally uses try_parse and unwraps the result to parse a single value from a source string.

scan

Interally uses try_scan and unwraps the result to parse multiple values from a source string.

try_parse

Attempts to parse a single variable from an iterator on a type that implements the TryParse trait.

try_scan

Very similar to try_parse, except it allows for 2 or more matched values.

Enums

TryParseError

Generic error type for parsing.

Traits

TryParse

Allows a type to be parsed through the try_parse, parse, try_scan and scan macros.