| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Text.Fixity.Internal
Description
Precedence-general machinery for deciding whether an expression needs to be wrapped in parentheses or not. Source code has comments on the approach used and how it compares to some other known approaches.
Synopsis
- data Associativity
- data FixityOver prec = Fixity {}
- data Direction
- data RenderContextOver prec = RenderContext {}
- encloseIn ∷ Ord prec ⇒ (a → a) → RenderContextOver prec → FixityOver prec → a → a
Documentation
data Associativity Source #
Associativity of an operator.
Constructors
| LeftAssociative | |
| RightAssociative | |
| NonAssociative |
Instances
| Show Associativity Source # | |
Defined in Text.Fixity.Internal | |
| Eq Associativity Source # | |
Defined in Text.Fixity.Internal Methods (==) ∷ Associativity → Associativity → Bool Source # (/=) ∷ Associativity → Associativity → Bool Source # | |
data FixityOver prec Source #
Fixity of an operator.
We allow unary operators to have associativity, because it's useful to distinguish
between an expression like -(-x) (unary minus, left-associative) and ~~b
(boolean NOT, right-associative).
Associativity of unary operators also matters when pretty-printing expressions like (-x) + y,
which is pretty-printed as -x + y, assuming unary minus has the same fixity as + (and both
the operators are left-associative). I.e. unary minus is handled just like the binary one:
(0 - x) + y is pretty-printed as 0 - x + y.
Postfix operators are handled similarly. E.g. if ! is left-associative, then (x!)! is
pretty-printed as x!! and if it's right-associative -- (x!)!.
The data type is parameterized, so that the user can choose precedence to be integer/fractional,
bounded/unbounded, etc (we could also allows operators to be partially or totally ordered, but
at the moment prec is required to implement Ord, i.e. it has to be totally ordered).
By default we go with bounded fractional precedence, see the main Text.Fixity module.
Constructors
| Fixity | |
Fields
| |
Instances
| Show prec ⇒ Show (FixityOver prec) Source # | |
Defined in Text.Fixity.Internal | |
| Eq prec ⇒ Eq (FixityOver prec) Source # | |
Defined in Text.Fixity.Internal Methods (==) ∷ FixityOver prec → FixityOver prec → Bool Source # (/=) ∷ FixityOver prec → FixityOver prec → Bool Source # | |
Direction in which pretty-printing goes. For example in x + y x is pretty-printed to the
left of + and y is pretty-printed to the right of +.
Constructors
| ToTheLeft | |
| ToTheRight |
data RenderContextOver prec Source #
A context that an expression is being rendered in.
Constructors
| RenderContext | |
Fields
| |
Instances
| HasRenderContext RenderContext Source # | |
Defined in Text.PrettyBy.Fixity Methods | |
| Show prec ⇒ Show (RenderContextOver prec) Source # | |
Defined in Text.Fixity.Internal | |
| Eq prec ⇒ Eq (RenderContextOver prec) Source # | |
Defined in Text.Fixity.Internal Methods (==) ∷ RenderContextOver prec → RenderContextOver prec → Bool Source # (/=) ∷ RenderContextOver prec → RenderContextOver prec → Bool Source # | |
Arguments
| ∷ Ord prec | |
| ⇒ (a → a) | Enclose a value of type |
| → RenderContextOver prec | An outer context. |
| → FixityOver prec | An inner fixity. |
| → a | |
| → a |
Enclose an a (using the provided function) if required or leave it as is.
The need for enclosing is determined from an outer RenderContext and the inner fixity.