The Const keyword



The Const keyword | parameters | record | expressions | Block
Pas2JS pascal source code
// ######## CASE I ######################## const ONE = 1; const TWO = ONE + ONE; const MINUS_ONE = -ONE; procedure WriteLnOut(Value: Integer = MINUS_ONE); begin Writeln(IntToStr(Value)); end; WriteLnOut(); WriteLnOut(TWO + MINUS_ONE - ONE); WriteLnOut(ONE); WriteLnOut(TWO); WriteLnOut($100); { <<<<<<<<<<<< CONSOLE OUTPUTS >>>>>>>>>>>>>>>>>>> -1 0 1 2 256 } // ######## CASE II ######################## const X = 1024; const Y = Round(X / 5); const Z = Trunc(X / 5); Writeln(IntToStr(Y)); Writeln(IntToStr(Z)); { <<<<<<<<<<<< CONSOLE OUTPUTS >>>>>>>>>>>>>>>>>>> 205 204 } // ######## CASE III ######################## // EMPTY ARRAY ----> VAR X CONST <----- //var ARR := []; Const ARR = []; var i := 0; try WriteLn(ARR[i]); except on E: Exception do WriteLn(E.Message); end; // ######## CASE IV ######################## // -----> CONST BLOCK <------- procedure Stuff1; const a = 1; b = 2; var c : Integer; d : Integer; begin c:=d; end; procedure Stuff2; var c : Integer; d : Integer; const a = 1; b = 2; begin c:=d; end; procedure Stuff3; var c : Integer; d : Integer; begin c:=d; end; procedure Stuff4; const a = 1; b = 2; begin end; // ######## CASE V ######################## // -----> CONST IN PARAMETERS <------- procedure Test(const i : Integer); begin WriteLn(i); end; Test(1); Test(1+2); var j = 10; Test(j+1); Test(2*j); Test(Round(j*PI)); { <<<<<<<<<<<< CONSOLE OUTPUTS >>>>>>>>>>>>>>>>>>> 1 3 11 20 31 } // ######## CASE VI ######################## // -----> CONST IN PARAMETERS II <------- type TRec = record Field: Integer; end; function Func1(const r: TRec): Integer; begin Result := r.Field; end; function Func2(const r: TRec): TRec; begin Result.Field := r.Field + 1; end; var r: TRec; Writeln(Func1(r)); Writeln(Func1(Func2(r))); r := Func2(r); Writeln(Func1(r)); Writeln(Func1(Func2(r))); { <<<<<<<<<<<< CONSOLE OUTPUTS >>>>>>>>>>>>>>>>>>> 0 1 1 2 } // ######## CASE VII ######################## // --- CONST with RECORD TYPE -- type TRec1 = record w, x, y: Integer; z: Float; Name: string; end; const c: TRec1 = (x: 1; y: 2; z: 3.1; Name: 'hello'); Writeln(c.w); Writeln(c.x); Writeln(c.y); Writeln(c.z); Writeln(c.Name); { <<<<<<<<<<<< CONSOLE OUTPUTS >>>>>>>>>>>>>>>>>>> 0 1 2 3.1 hello }