Hi !
Working with string is always a nice topic to learn. Itβs nice to understand how a specific language process strings, sometimes small changes can have big performance improvements !
String Interpolation
So letβs start (via Wikipedia) with some basic concepts.
In computer programming, string interpolation (or variable interpolation, variable substitution, or variable expansion) is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. It is a form of simple template processing[1] or, in formal terms, a form of quasi-quotation (or logic substitution interpretation). The placeholder may be a variable name, or in some languages an arbitrary expression, in either case evaluated in the current context.
String interpolation is an alternative to building string via concatenation, which requires repeated quoting and unquoting;[2] or substituting into a printf format string, where the variable is far from where it is used. Compare:
apples = 4
print("I have ${apples} apples.") # string interpolation
print("I have " + apples + " apples.") # string concatenation
print("I have %s apples.", apples) # format string
String Interpolation in Rust
Rust does not have general string interpolation, but provides similar functionality via macros. Rust provides formatting via the std::fmt module, which is interfaced with through various macros such as format!, write!, and print!.
The hello world example may look like this one:
These macros are converted into Rust source code at compile-time, whereby each argument interacts with a formatter. The formatter supports positional parameters, named parameters, argument types, defining various formatting traits, and capturing identifiers from the environment.
We can also work with implicit named arguments. I like this option, the code is easier to read.
/* | |
Copyright (c) 2023 | |
Author : Bruno Capuano | |
Create Time : 2023 January | |
Change Log : | |
- Working with strings with strucs and named arguments | |
The MIT License (MIT) | |
Permission is hereby granted, free of charge, to any person obtaining a copy | |
of this software and associated documentation files (the "Software"), to deal | |
in the Software without restriction, including without limitation the rights | |
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
copies of the Software, and to permit persons to whom the Software is | |
furnished to do so, subject to the following conditions: | |
The above copyright notice and this permission notice shall be included in | |
all copies or substantial portions of the Software. | |
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
THE SOFTWARE. | |
*/ | |
struct Pet { | |
name: String, | |
age: u8, | |
} | |
fn main() { | |
let pet_ace = Pet { | |
name: String::from("ACE"), | |
age: 1, | |
}; | |
// println!("{pet_ace.name} the pet is {pet_ace.age} years old."); | |
// Trigger this error: | |
// println!("{pet_ace.name} the pet is {pet_ace.age} years old."); | |
// ^^^^^^^^^^^^ not supported in format string | |
println!("{} the pet is {} years old.", pet_ace.name, pet_ace.age); | |
// Expected output: ACE the pet is 1 years old. | |
} |
At this moment, I think Iβll read more about the way Rust works with Strings. Mostly in the official Rust Documentation for Strings.
Happy coding!
Greetings
El Bruno
More posts in my blog ElBruno.com.
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