Basic Haskell: simple data types

 

 Functional Programming in Haskell
3rd CCSC Northwest Conference • Fall 2001

Basic Haskell: simple data types
bullet Ints and Integers
The default Integer type in Haskell provides for very large numbers 
> 2 ^ 100
1267650600228229401496703205376
> 2 ^ 200

1606938044258990275541962092341162602522202993782792835301376

(there is also a more efficient and traditional Int type)

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 Functional Programming in Haskell
3rd CCSC Northwest Conference • Fall 2001

Basic Haskell: simple data types
bullet Ints and Integers
bullet Floating-point arithmetic
Traditional IEEE floating-point arithmetic is also available (with the usual caveats) 
> 2.3 ^ 5
64.36343

> $$ * 25.333
1630.51877

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 Functional Programming in Haskell
3rd CCSC Northwest Conference • Fall 2001

Basic Haskell: simple data types
bullet Ints and Integers
bullet Floating-point arithmetic
bullet Exact rational arithmetic
Haskell provides exact rational numbers (written with an infix "%") as a safer alternative to floating-point 
> 51 % 3
17 % 1

> (51 % 3) * (2 % 5)
34 % 5

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 Functional Programming in Haskell
3rd CCSC Northwest Conference • Fall 2001

Basic Haskell: simple data types
bullet Ints and Integers
bullet Floating-point arithmetic
bullet Exact rational arithmetic
bullet Booleans and if expressions
The usual boolean values are written with initial caps; the conditional construct is an expression, not a statement 
> if 3 < 2 then "oops" else "hurray!"
"hurray!"

> (if 3 < 2 then "oops" else "hurray!") ++ " arithmetic works!"
"hurray! arithmetic works!"

> (if 3 < 2 then (+) else (*)) 10 20
200

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 Functional Programming in Haskell
3rd CCSC Northwest Conference • Fall 2001

Basic Haskell: simple data types
bullet Ints and Integers
bullet Floating-point arithmetic
bullet Exact rational arithmetic
bullet Booleans and if expressions
bullet Pairs and tuples
Unlike most languages, Haskell provides pairs and tuples as independent entities (e.g., to return multiple results) 
> fst (2, "foo")
2

> 17 `divMod` 3
(5,2)

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 Functional Programming in Haskell
3rd CCSC Northwest Conference • Fall 2001

Basic Haskell: simple data types
bullet Ints and Integers
bullet Floating-point arithmetic
bullet Exact rational arithmetic
bullet Booleans and if expressions
bullet Pairs and tuples
bullet The Maybe type
The Maybe datatype marks values as either Nothing or "Just" a single value; this allows for a natural light-weight exception mechanism 
> lookup "sam" [("amy", 25), ("fred", 1), ("sam", 2)]
Just 2

> lookup "jim" [("amy", 25), ("fred", 1), ("sam", 2)]
Nothing

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