String interpolation
0 likes1,248 views
This document provides an overview of string interpolation in Scala, detailing its definition and types: 's', 'raw', and 'f' interpolators. It explains how these interpolators function, with examples, and highlights their differences, such as processing of escape sequences and formatting. Additionally, it covers the use of implicit classes for extension methods and includes references for further exploration.
![Knowing the internals
println(s"$name is $age years old and earns ₹ $salary")
println(new StringContext(""," is ", " years old and earns
","").₹ s(name,age,salary))
parts.length == args.length + 1 (Or IllegalArgumentException)
(Compile Time Reflection)
‘Parts’ of type Seq[String]‘Args’ of type Seq[Any]](https://image.slidesharecdn.com/stringinterpolation-ppt-160923061032/85/String-interpolation-10-320.jpg)
![Knowing the internals
println(raw"$name t is $age years old n”)
println(new StringContext(""," t is ", " years old n","")
.raw(name,age))
parts.length == args.length + 1 (Or IllegalArgumentException)
(Compile Time Reflection)
‘Parts’ of type Seq[String]‘Args’ of type Seq[Any]](https://image.slidesharecdn.com/stringinterpolation-ppt-160923061032/85/String-interpolation-13-320.jpg)
: String = macro ???
Its implementation is hardwired to →
`scala.tools.reflect.MacroImplementations.macro_StringI
nterpolation_f`](https://image.slidesharecdn.com/stringinterpolation-ppt-160923061032/85/String-interpolation-15-320.jpg)
![Knowing the internals
println(f"$name t earns $salary%3.2f at $hour%02d n”)
println(new StringContext(""," t earns ", "%3.2f at
","%02d n") .f(name,salary,hour))
parts.length == args.length + 1 (Or corresponding error message)
(Compile Time Reflection)
‘Parts’ of type List[Tree]‘Args’ of type List[Tree]](https://image.slidesharecdn.com/stringinterpolation-ppt-160923061032/85/String-interpolation-16-320.jpg)
String interpolation
- 1. String Interpolation SAHIL SAWHNEY Software Consultant KNOLDUS SOFTWARE LLP SAHIL SAWHNEY Software Consultant KNOLDUS SOFTWARE LLP
- 2. Agenda ● What is string interpolation ● Types of string interpolation ● Exploring each type ● Case study
- 3. What are we going to learn? ➔ What we want to do here? Compose a string by concatenating values (variables and constants) in it. ➔ What we are actually doing here? Inducing the ‘Yuck Factor’
- 4. What is interpolation? “To put (words) into a piece of writing or a conversation” -Merriam Webster So what shall string interpolation in Scala mean?
- 5. String Interpolation in scala ➔ It is a mechanism that enable us to sew/embed/bind WORDS in between a processed/unprocessed string literal. ➔ Here by processed string literal we mean processing of meta-characters like escape sequences(n, t, r etc.) in the string.
- 6. What these ‘WORDS’ are? ➔Variables and constants var a =5; val b=55; ➔Result yielding expressions Match case If-else Try-catch You name it.
- 7. The three mess saviors ➔ The ‘s’ interpolator (Simple string interpolator). ➔ The ‘raw’ interpolator (Raw string interpolator). ➔ The ‘f’ interpolator (Formatted string interpolator). Powered by - ‘StringContext’ class.
- 8. ‘s’ interpolator ➔ To use this interpolator just prepend the string with an ‘s’ and put a ‘$’ sign before the values to be embedded(‘${}’ for the expression). CAUTION → Just take care there are no spaces between the ‘$’ and the variable.
- 9. What exactly ‘s’ is? ➔ ‘s’ is actually a method of ‘StringContext’ class with the following signature :- def s(args: Any*): String = standardInterpolator(treatEscapes, args) ‘args’ are the arguments to be inserted into resulting string. ‘treatescape’ is the partial function that process the string by applying escape sequence if any.
- 10. Knowing the internals println(s"$name is $age years old and earns ₹ $salary") println(new StringContext(""," is ", " years old and earns ","").₹ s(name,age,salary)) parts.length == args.length + 1 (Or IllegalArgumentException) (Compile Time Reflection) ‘Parts’ of type Seq[String]‘Args’ of type Seq[Any]
- 11. ‘raw’ interpolator ➔ It is similar to ‘s’ interpolator except for one difference i.e. it do not process the string. ➔ It just embed the value in a raw (unprocessed) string literal.
- 12. I think we know whats ‘raw’. ➔ Like ‘s’, ‘raw’ is also a method of StringContext class with following signature :- def raw(args: Any*): String = standardInterpolator(identity, args) ➔ ‘args’ are the arguments to be inserted into resulting string ➔ ‘identity’ is a method in ‘Predef.scala’ that returns the same value what it gets as a parameter.
- 13. Knowing the internals println(raw"$name t is $age years old n”) println(new StringContext(""," t is ", " years old n","") .raw(name,age)) parts.length == args.length + 1 (Or IllegalArgumentException) (Compile Time Reflection) ‘Parts’ of type Seq[String]‘Args’ of type Seq[Any]
- 14. ‘f’ interpolator ➔ It is based on the printf method used in java and is used to format the string. ➔ It also process the string before embedding the values. ➔ All values should be immediately followed by a printf-style format string. ➔ The f interpolator is type-safe. ➔ If no format is specified, String(%s) is considered to be the default format.
- 15. We definitely know what ‘f’ is ➔ Yes, it is also a method of StringContext class but with a twist :- def f[A >: Any](args: A*): String = macro ??? Its implementation is hardwired to → `scala.tools.reflect.MacroImplementations.macro_StringI nterpolation_f`
- 16. Knowing the internals println(f"$name t earns $salary%3.2f at $hour%02d n”) println(new StringContext(""," t earns ", "%3.2f at ","%02d n") .f(name,salary,hour)) parts.length == args.length + 1 (Or corresponding error message) (Compile Time Reflection) ‘Parts’ of type List[Tree]‘Args’ of type List[Tree]
- 18. To be noted When do we need an implicit class? When we need to implement extension methods for an existing class. Example :- class MyInt(value:Int){ def kamehameha:Int={value * 10000000000} } 5.kamehameha → new MyInt(5).kamehameha
- 19. The flow write”$name is $age years oldnand earns $salary”₹ new StringContext(“”, ” is “,” years oldnand earns ₹ “,””).write(name, age,salary) new WriteScore(new StringContext(“”, ” is “,” years oldnand earns “,””).write(name, age,salary))₹ (Compile Time) (Rewriting implicit class)
- 21. Any Questions?