Conversion of values to readable Strings.
Minimal complete definition: showsPrec or show.
Derived instances of Show have the following properties, which are compatible with derived instances of Text.Read.Read:
* The result of show is a syntactically correct Haskell expression containing only constants, given the fixity declarations in force at the point 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)
> showsPrec d (Leaf m) = showParen (d > app_prec) $
> showString "Leaf " . showsPrec (app_prec+1) m
> showsPrec d (u (:^:) v) = showParen (d > up_prec) $
> showsPrec (up_prec+1) u .
> showString " (:^:) " .
> showsPrec (up_prec+1) v
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)".
Converting values to readable strings: the Show class and associated functions.
The shows functions return a function that prepends the output String to an existing String. This allows constant-time concatenation of results using function composition.
utility function converting a Char to a show function that simply prepends the character unchanged.
utility function that surrounds the inner show function with parentheses when the Bool parameter is True.
equivalent to showsPrec with a precedence of 0.
utility function converting a String to a show function that simply prepends the string unchanged.
Gets the string for a constructor
Show a signed RealFloat value using scientific (exponential) notation (e.g. 2.45e2, 1.5e-3).
In the call showEFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.
Show a signed RealFloat value using standard decimal notation (e.g. 245000, 0.0015).
In the call showFFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.
First arg is whether to chop off trailing zeros
Show a signed RealFloat value to full precision using standard decimal notation for arguments whose absolute value lies between 0.1 and 9,999,999, and scientific notation otherwise.
Show a signed RealFloat value using standard decimal notation for arguments whose absolute value lies between 0.1 and 9,999,999, and scientific notation otherwise.
In the call showGFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.
Show non-negative Integral numbers in base 16.
Show non-negative Integral numbers in base 10.
Shows a non-negative Integral number using the base specified by the first argument, and the character representation specified by the second.
Show a list (using square brackets and commas), given a function for showing elements.
Convert a character to a string using only printable characters, using Haskell source-language escape conventions. For example:
> showLitChar '\n' s = "\\n" ++ s
Show non-negative Integral numbers in base 8.
Converts a possibly-negative Real value to a string.
Provides one possible concrete representation for Version. For a version with versionBranch = [1,2,3] and versionTags = ["tag1","tag2"], the output will be 1.2.3-tag1-tag2.
hShow is in the IO monad, and gives more comprehensive output than the (pure) instance of Show for Handle.
Like trace, but uses show on the argument to convert it to a String.
> traceShow = trace . show