Show package:clash-prelude

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)".

A specialised variant of showsPrec, using precedence context zero, and returning an ordinary String.

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.

Like the Show class, but values that normally throw an XException are converted to undefined, instead of error'ing out with an exception.

>>> show (errorX "undefined" :: Integer, 4 :: Int)
"(*** Exception: X: undefined
CallStack (from HasCallStack):
...

>>> showX (errorX "undefined" :: Integer, 4 :: Int)
"(undefined,4)"

Can be derived using Generics:

{-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}

import Clash.Prelude
import GHC.Generics

data T = MkTA Int | MkTB Bool
deriving (Show,Generic,ShowX)

utility function converting a Char to a show function that simply prepends the character unchanged.

The method showList is provided to allow the programmer to give a specialised way of showing lists of values. For example, this is used by the predefined Show instance of the Char type, where values of type String should be shown in double quotes, rather than between square brackets.

utility function that surrounds the inner show function with parentheses when the Bool parameter is True.

utility function converting a String to a show function that simply prepends the string unchanged.

equivalent to showsPrec with a precedence of 0.

Convert a value to a readable String. showsPrec should satisfy the law

showsPrec d x r ++ s  ==  showsPrec d x (r ++ s)

Derived instances of Read and Show satisfy the following:

• (x,"") is an element of (readsPrec d (showsPrec d x "")).

That is, readsPrec parses the string produced by showsPrec, and delivers the value that showsPrec started with.

Show a base-2 encoded natural as a binary literal NB: The LSB is shown as the right-most bit

>>> d789
d789

>>> toBNat d789
b789

>>> showBNat (toBNat d789)
"0b1100010101"

>>> 0b1100010101 :: Integer
789

Like showList, but values that normally throw an XException are converted to undefined, instead of error'ing out with an exception.

Like show, but values that normally throw an XException are converted to undefined, instead of error'ing out with an exception.

Like showsPrec, but values that normally throw an XException are converted to undefined, instead of error'ing out with an exception.

Like showsPrec, but values that normally throw an XException are converted to undefined, instead of error'ing out with an exception.

Use when you want to create a ShowX instance where:

• There is no Generic instance for your data type
• The Generic derived ShowX method would traverse into the (hidden) implementation details of your data type, and you just want to show the entire value as undefined.

Can be used like:

data T = ...

instance Show T where ...

instance ShowX T where
showsPrecX = showsPrecXWith showsPrec

Like shows, but values that normally throw an XException are converted to undefined, instead of error'ing out with an exception.

Creates an instance of the form: instance (ShowX a0, ShowX a1) => ShowX (a0, a1) With n number of variables.

Creates instances of ShowX for all tuple sizes listed. See mkShowXTupleInstance for more information.