From Wikipedia, the free encyclopedia

BLooP and FLooP are simple programming languages designed by Douglas Hofstadter to illustrate a point in his book Gödel, Escher, Bach. BLooP is a non-Turing-complete programming language whose only control flow structure is a bounded loop. This language can only express primitive recursive functions. FLooP is identical except that it supports unbounded loops; it is a Turing-complete language. These can be regarded as primitive models of computation.

BLooP examples

Note: The only variables are output (the return value of the procedure) and cell(i) (an infinite array of integers). The only operators are ⇐ (assignment), + (addition), × (multiplication), < (less-than), > (greater-than) and = (equals).

Factorial function:

DEFINE PROCEDURE ''FACTORIAL'' [N]:
BLOCK 0: BEGIN
        OUTPUT ⇐ 1;
        CELL(0) ⇐ 1;
        LOOP N TIMES:
        BLOCK 1: BEGIN
                OUTPUT ⇐ OUTPUT × CELL(0);
                CELL(0) ⇐ CELL(0) + 1;
        BLOCK 1: END;
BLOCK 0: END.

Subtraction function (this is not a built-in operation):

DEFINE PROCEDURE ''MINUS'' [M,N]:
BLOCK 0: BEGIN
        IF M < N, THEN:
        QUIT BLOCK 0;
        LOOP AT MOST M + 1 TIMES:
        BLOCK 1: BEGIN
                IF OUTPUT + N = M, THEN:
                ABORT LOOP 1;
                OUTPUT ⇐ OUTPUT + 1;
        BLOCK 1: END;
BLOCK 0: END.

External links

• Dictionary of Programming Languages - BLooP
• Dictionary of Programming Languages - FLooP
• The Retrocomputing Museum
• Portland Pattern Repository: Bloop Floop and Gloop
• A compiler for BlooP and FlooP
• An online interpreter for BlooP and FlooP