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Small Small Basic Parser FParsec sample
// Type abbreviations
type label = string
type identifier = string
type index = int
type HashTable<'k,'v> = System.Collections.Generic.Dictionary<'k,'v>
/// Small Basic arithmetic operation
type arithmetic = Add | Subtract | Multiply | Divide
/// Small Basic comparison operaton
type comparison = Eq | Ne | Lt | Gt | Le | Ge
/// Small Basic logical operation
type logical = And | Or
/// Small Basic value
type value =
| Bool of bool
| Int of int
| Double of double
| String of string
| Array of HashTable<value,value>
/// Small Basic expression
type expr =
| Literal of value
| Var of identifier
| GetAt of location
| Func of invoke
| Neg of expr
| Arithmetic of expr * arithmetic * expr
| Comparison of expr * comparison * expr
| Logical of expr * logical * expr
and location =
| Location of identifier * expr list
and invoke =
| Method of string * string * expr[]
| PropertyGet of string * string
/// Small Basic assignment
type assign =
| Set of identifier * expr
/// Small Basic instruction
type instruction =
| Assign of assign
| SetAt of location * expr
| PropertySet of string * string * expr
| Action of invoke
| For of assign * expr * expr
| EndFor
| If of expr
| ElseIf of expr
| Else
| EndIf
| While of expr
| EndWhile
| Sub of identifier
| EndSub
| GoSub of identifier
| Label of label
| Goto of label
#r @"..\packages\FParsec.1.0.1\lib\net40-client\FParsecCS.dll"
#r @"..\packages\FParsec.1.0.1\lib\net40-client\FParsec.dll"
open FParsec
let ptrue = stringReturn "true" true
let pfalse = stringReturn "false" false
let pbool = (ptrue <|> pfalse) |>> fun x -> Bool(x)
let pint = pint32 |>> fun n -> Int(n)
let pvalue = pbool <|> pint
let pliteral = pvalue |>> fun x -> Literal(x)
let pidentifier =
let isIdentifierFirstChar c = isLetter c || c = '_'
let isIdentifierChar c = isLetter c || isDigit c || c = '_'
many1Satisfy2L isIdentifierFirstChar isIdentifierChar "identifier"
let pvar = pidentifier |>> fun name -> Var(name)
let pexpr = pliteral <|> pvar
let pset = pipe3 pidentifier (pstring "=") pexpr (fun id _ e -> Set(id, e))
let pfor =
let pfrom = pstring "For" >>. spaces1 >>. pset .>> spaces1
let pto = pstring "To" >>. spaces1 >>. pexpr
let pstep = pstring "Step" >>. spaces1 >>. pexpr
let toStep = function None -> Literal(Int(1)) | Some s -> s
pipe3 pfrom pto (opt pstep) (fun f t s -> For(f, t, toStep s))
let pstatement =
choice [
attempt pfor
// ... other statements
]
run pfor "For A=1 To 100"
let pcomment =
pchar '\'' >>. skipManySatisfy (fun c -> c <> '\n') >>. pchar '\n'
let peol = pcomment <|> (pchar '\n')
let plines = many (spaces >>. pstatement .>> peol) .>> eof
let parse (program:string) =
match run plines program with
| Success(result, _, _) -> result
| Failure(errorMsg, e, s) -> failwith errorMsg
let program =
parse """For A=1 To 100
"""
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