程序代做CS代考 Haskell interpreter interpreter tweaks – cscodehelp代写

interpreter tweaks
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Overview.md 1.77 KB
Implementing a small imperative language
We implement an interpreter for a small imperative programming language. Example
This is the sample file fibonacci.xy:
{
y := 0;
z := 1;
while (x > 0)
{
x := x – 1; t := y + z; y := z;
z := t;
} }
There are no IO commands in our language. The input is in the variable x and the output is in the variable y . Hence we call our language xy . We run this as follows:
$ runhaskell Runxy.hs fibonacci.xy 11
89
Overall structure
Given a program source code, that is, a String , in concrete syntax as above: We parse it, to produce a program tree in abstract syntax.
Given this and an initial storage, that is, an assignment of values to program variables, we run the program to get a new storage.
| initial
| storage
v final
source code +———–+ program tree +——-+——–+ storage
———————>| Parser.hs | ——————–>| Interpreter.hs | ——–>
(concrete syntax) +———–+ (AbstractSyntax.hs) +—————-+
(a string)
We use a program Runxy.hs to read a file into a String and read a value x from the command line arguments, which then calls the parser and then the interpreter, with an initial storage assigning the value x to the program variable “x” and finally prints the value of the variable “y” , as in the above example.
Next: Concrete syntax