Haskell CW
To compile:
alex Lexer.x to compile the alex
happy Parser.y to compile the happy
ghc Main
(These only need doing if you changed the lexer / parser / main)\
To run:
./Main <input file> <program>
eg. to run problem 3
./Main problems/3/input.txt problems/3/program.txt
#Language Design Programs are designed to take an input of streams, and output a stream of numbers\
The input of streams is provided as the first command line argument, which is read from a file
To output a number in the program, use the push method
eg. program.txt containing push 5 and running that on any input, will result in 5
note: push also can accept a list of numbers to add to the output
To access the input streams, there are reserved variable names in the format S<stream number>
eg. for the first problem input, S1 is defined as 1, 2, 3, 4
##Variables
To define a variable, use the let keyword
eg. let x = 5
x can now be used throughout the program
eg. push x
would now put 5 into the output
To reassign a variable, the let keyword isn't needed
eg. x = 9
The value of x is now 9
##Arithmetic
All basic arithmetic operators are available: + - * / ^ %
As these programs only deal with integers, the division rounds down.
eg. let x = 5 + 9 push x
Will put 14 in the output
Assignment operators are all also available
eg x += 6
##Lists
The only type of list is a list of ints. The reserved variables for the input streams store a list of ints
To access an element of an array, use the <list> at <index> syntax
eg. for the first problem input, S1 has the value: 1, 2, 3, 4 therefore
S1 at 0 will return 1
The length keyword can be used to get the length of a list
eg. length S1 will return 4
Lists cannot currently be created easily, however a list can be created using the range function
The syntax for the range function is range <start> <end>
eg. range 0 10 will return 0,1,2,3,4,5,6,7,8,9,10
#Loops
For loops can be created with the for <var> in <list>{ } syntax
eg. for x in (range 0 10){ push x }
Will result in the numbers 0 - 10 to be added to the output