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[ 0 => '= Letterfuck =', 1 => '', 2 => ''''Letterfuck''' (LF) is an esoteric programming language inspired by [[Brainfuck]] and [[Piet]], but using letters as commands. LF combines a ''memory tray'' similar to Brainfuck with a [[Stack (data structure)|stack]] like Piet. Programs are sequences of letters, with the differences between letters encoding commands and repeated letters forming blocks.', 3 => '', 4 => '== Overview ==', 5 => 'LF programs use a memory tray (array of cells) and a stack (LIFO). Each command is represented by the change in letters. <br> ', 6 => '- Syntax (bytecode): aAbB', 7 => '* a is a parameter for the current command ', 8 => '* b is a parameter for the next command ', 9 => '* A,B are letters from A-Z ', 10 => '- Opcode = index(B) - index(A) if B > A, or 26 + index(B) - index(A) if B < A. ', 11 => '- Repeated letters form a ''block'', with size representing the parameter for some commands.', 12 => '- Example: AAAB does command 1, parameter 3', 13 => '', 14 => '== Commands ==', 15 => '{| class="wikitable"', 16 => '! STT !! Command !! Param !! Description', 17 => '|-', 18 => '| 1 || IDXINC || VAL || Increase memory index: index += VAL', 19 => '|-', 20 => '| 2 || IDXDEC || VAL || Decrease memory index: index -= VAL', 21 => '|-', 22 => '| 3 || INC || VAL || Add VAL to current cell: tray[index] += VAL', 23 => '|-', 24 => '| 4 || DEC || VAL || Subtract VAL from current cell: tray[index] -= VAL', 25 => '|-', 26 => '| 5 || IN(CHAR) || NONE || Input a character: tray[index] = ASCII(input_char())', 27 => '|-', 28 => '| 6 || ZERO (ZZ) || NONE || Next command receives 0 or ZZ (boolean false) as parameter', 29 => '|-', 30 => '| 7 || IN(NUM) || NONE || Input a number: tray[index] = input_number()', 31 => '|-', 32 => '| 8 || OUT(CHAR) || CELL || Output ASCII character: system.write(tray[index])', 33 => '|-', 34 => '| 9 || OUT(NUM) || CELL || Output number: system.write(tray[index])', 35 => '|-', 36 => '| 10 || NEG || VAL || Negation: NEG a = -a; if a=ZZ → 1; number ≥1 → TRUE', 37 => '|-', 38 => '| 11 || STARTLOOP || VAL || Loop VAL times', 39 => '|-', 40 => '| 12 || ENDLOOP || NONE || End loop', 41 => '|-', 42 => '| 13 || EQ || VAL || Compare top of stack with VAL: 1 if equal, ZZ if not', 43 => '|-', 44 => '| 14 || BRK || NONE || Break loop', 45 => '|-', 46 => '| 15 || WHILE || VAL || While VAL=1, repeat loop', 47 => '|-', 48 => '| 16 || ENDWHILE || NONE || End while loop', 49 => '|-', 50 => '| 17 || PUSH || CELL || Push cell to stack, reset cell', 51 => '|-', 52 => '| 18 || POP || STACK || Pop stack to cell', 53 => '|-', 54 => '| 19 || CMP || STACK || Compare top two stack values', 55 => '|-', 56 => '| 20 || DUP || STACK || Duplicate top of stack', 57 => '|-', 58 => '| 21 || SUB || STACK || Subtract top stack values', 59 => '|-', 60 => '| 22 || ADD || STACK || Add top stack values', 61 => '|-', 62 => '| 23 || MUL || STACK || Multiply top stack values', 63 => '|-', 64 => '| 24 || DIV || STACK || Divide top stack values', 65 => '|-', 66 => '| 25 || END || NONE || End program', 67 => '|}', 68 => '', 69 => '== LFSP and LFASM ==', 70 => 'LF is hard to read, so two helper syntaxes exist:', 71 => '', 72 => '* '''LFSP''' (LF-Simplified): compresses repeated letters. Example:', 73 => 'AAAAAAAAALLLLLLLLOAIH → 9A8LOAIH', 74 => '', 75 => '* '''LFASM''' (LF Assembly): easier coding:', 76 => '9A8LOAIH → STARTLOOP 9, INC 8, ENDLOOP, OUT(CHAR), END', 77 => '', 78 => '= LF-High (LFH) =', 79 => '', 80 => 'LF-High is an advanced version of LF with major improvements:', 81 => '* Compact commands:', 82 => '** in, form, dest (opcode 5)', 83 => '** out, form, target, start, end (opcode 8)', 84 => '** idx, val (val can be negative) (opcode 1)', 85 => '** inc, val, ... (val can be negative, supports increasing multiple cells at once) (opcode 3)', 86 => '* New commands (to fill in the spot of: IDXDEC, DEC, IN(NUM), OUT(NUM)):', 87 => '** mov, pt, val (opcode 2)', 88 => '** sel, target (opcode 4)', 89 => '* Zone support with flags:', 90 => '** ^ → start zone', 91 => '** !! → end zone', 92 => '** # → zone pointer', 93 => '** $ → self (current zone)', 94 => '* Advanced stack operations, select stack, arithmetic on stack and cell. Local pointers for zones, and stack pointer (sp).', 95 => '', 96 => '=== Example that includes all of the new commands ===', 97 => '<pre>', 98 => 'inc, ^4 // start zone and makes the first value 4', 99 => 'sel, $ // select current cell', 100 => 'idx, 2', 101 => 'inc, !!9', 102 => 'sel, $', 103 => 'add // adds the 2 selected cells', 104 => 'out, num, sp // outs 13', 105 => 'end', 106 => '</pre>', 107 => 'Output: <code>13</code>', 108 => '', 109 => '* $ references the current zone or the current cell, depending on instruction:', 110 => '{| class="wikitable"', 111 => '|+ Caption text', 112 => '|-', 113 => '! Instructions !! $ means', 114 => '|-', 115 => '| add, sub, mul, div || current cell', 116 => '|-', 117 => '| out || current zone', 118 => '|}', 119 => '', 120 => '== Advantages and disadvantages ==', 121 => '* '''Advantages''': Very powerful; supports self-replicating code, complex stack operations, and zones.', 122 => '* '''Disadvantages''': Difficult to read and debug, requires hard thinking and wise coding.', 123 => '', 124 => '== See also ==', 125 => '* [[Brainfuck]]', 126 => '* [[Piet]]' ]