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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.
Variables in standard JavaScript have no type attached, so any value (each value has a type) can be stored in any variable. Starting with ES6 , the 6th version of the language, variables could be declared with var for function scoped variables, and let or const which are for block level variables.
One of the oldest examples is in shell scripts, where single quotes indicate a raw string or "literal string", while double quotes have escape sequences and variable interpolation. For example, in Python , raw strings are preceded by an r or R – compare 'C:\\Windows' with r'C:\Windows' (though, a Python raw string cannot end in an odd number ...
The delimiters around the tag have the same effect within the here doc as they would in a regular string literal: For example, using double quotes around the tag allows variables to be interpolated, but using single quotes doesn't, and using the tag without either behaves like double quotes. Using backticks as the delimiters around the tag runs ...
A string substitution or simply a substitution is a mapping f that maps characters in Σ to languages (possibly in a different alphabet). Thus, for example, given a character a ∈ Σ, one has f(a)=L a where L a ⊆ Δ * is some language whose alphabet is Δ. This mapping may be extended to strings as f(ε)=ε
For example, () is a rewrite rule, commonly used to establish a normal form with respect to the associativity of . That rule can be applied at the numerator in the term a ∗ ( ( a + 1 ) ∗ ( a + 2 ) ) 1 ∗ ( 2 ∗ 3 ) {\displaystyle {\frac {a*((a+1)*(a+2))}{1*(2*3)}}} with the matching substitution { x ↦ a , y ↦ a + 1 , z ↦ a + 2 ...
Polymorphic types can become monomorphic by consistent substitution of their variables. Examples of monomorphic instances are: id' : String -> String nil' : List Number More generally, types are polymorphic when they contain type variables, while types without them are monomorphic.
A substitution σ is called a linear substitution if tσ is a linear term for some (and hence every) linear term t containing precisely the variables of σ ' s domain, i.e. with vars(t) = dom(σ). A substitution σ is called a flat substitution if xσ is a variable for every variable x. A substitution σ is called a renaming substitution if it ...