show package:ghc-lib-parser
A specialised variant of
showsPrec, using precedence context
zero, and returning an ordinary
String.
Conversion of values to readable
Strings.
Derived instances of
Show have the following properties, which
are compatible with derived instances of
Read:
- The result of show is a syntactically correct Haskell
expression containing only constants, given the fixity declarations in
force at the point where the type is declared. It contains only the
constructor names defined in the data type, parentheses, and spaces.
When labelled constructor fields are used, braces, commas, field
names, and equal signs are also used.
- If the constructor is defined to be an infix operator, then
showsPrec will produce infix applications of the
constructor.
- the representation will be enclosed in parentheses if the
precedence of the top-level constructor in x is less than
d (associativity is ignored). Thus, if d is
0 then the result is never surrounded in parentheses; if
d is 11 it is always surrounded in parentheses,
unless it is an atomic expression.
- If the constructor is defined using record syntax, then
show will produce the record-syntax form, with the fields given
in the same order as the original declaration.
For example, given the declarations
infixr 5 :^:
data Tree a = Leaf a | Tree a :^: Tree a
the derived instance of
Show is equivalent to
instance (Show a) => Show (Tree a) where
showsPrec d (Leaf m) = showParen (d > app_prec) $
showString "Leaf " . showsPrec (app_prec+1) m
where app_prec = 10
showsPrec d (u :^: v) = showParen (d > up_prec) $
showsPrec (up_prec+1) u .
showString " :^: " .
showsPrec (up_prec+1) v
where up_prec = 5
Note that right-associativity of
:^: is ignored. For example,
- show (Leaf 1 :^: Leaf 2 :^: Leaf 3) produces the
string "Leaf 1 :^: (Leaf 2 :^: Leaf 3)".
Show the tree that implements the map. The tree is shown
in a compressed, hanging format.
The expression (
showTreeWith hang wide
map) shows the tree that implements the map. If
hang is
True, a
hanging tree is shown otherwise a rotated tree
is shown. If
wide is
True, an extra wide version is
shown.
Show the tree that implements the set. The tree is shown
in a compressed, hanging format.
The expression (
showTreeWith hang wide
map) shows the tree that implements the set. If
hang is
True, a
hanging tree is shown otherwise a rotated tree
is shown. If
wide is
True, an extra wide version is
shown.
Show a SDoc as a String with the default user style
Allows caller to specify the NamePprCtx to use
Show a GHC syntax tree. This parameterised because it is also used for
comparing ASTs in ppr roundtripping tests, where the SrcSpan's are
blanked out, to avoid comparing locations, only structure
Show the full AST as the compiler sees it.
Show a declaration but not its RHS.
Show declaration and its RHS, including GHc-internal information (e.g.
for --show-iface).
utility function converting a
Char to a show function that
simply prepends the character unchanged.