Symbol package:base

Haskell symbol, e.g. >>, :%

(Kind) This is the kind of type-level symbols.

Sc: Symbol, Currency

Sm: Symbol, Math

Sk: Symbol, Modifier

So: Symbol, Other

Selects Unicode symbol characters, including mathematical and currency symbols. This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

• MathSymbol
• CurrencySymbol
• ModifierSymbol
• OtherSymbol

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Symbol".

Examples

Basic usage:

>>> isSymbol 'a'
False

>>> isSymbol '6'
False

>>> isSymbol '='
True

The definition of "math symbol" may be a little counter-intuitive depending on one's background:

>>> isSymbol '+'
True

>>> isSymbol '-'
False

Concatenation of type-level symbols.

Comparison of type-level symbols, as a function.

Extending a type-level symbol with a type-level character

This class gives the string associated with a type-level symbol. There are instances of the class for every concrete literal: "hello", etc.

A value-level witness for a type-level symbol. This is commonly referred to as a singleton type, as for each s, there is a single value that inhabits the type SSymbol s (aside from bottom). The definition of SSymbol is intentionally left abstract. To obtain an SSymbol value, use one of the following:

1. The symbolSing method of KnownSymbol.
2. The SSymbol pattern synonym.
3. The withSomeSSymbol function, which creates an SSymbol from a String.

A explicitly bidirectional pattern synonym relating an SSymbol to a KnownSymbol constraint. As an expression: Constructs an explicit SSymbol s value from an implicit KnownSymbol s constraint:

SSymbol @s :: KnownSymbol s => SSymbol s

As a pattern: Matches on an explicit SSymbol s value bringing an implicit KnownSymbol s constraint into scope:

f :: SSymbol s -> ..
f SSymbol = {- KnownSymbol s in scope -}

This type represents unknown type-level symbols.

This type family yields type-level Just storing the first character of a symbol and its tail if it is defined and Nothing otherwise.

Like sameSymbol, but if the symbols aren't equal, this additionally provides proof of LT or GT.

We either get evidence that this function was instantiated with the same type-level symbols, or that the type-level symbols are distinct.

Return the String corresponding to s in an SSymbol s value.