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4215
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1 %%% THE PLOKI LANGUAGE: INSTRUCTIONS %%%
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2
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3
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4 Execution starts at the first line of the program. Instructions are executed
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5 in the order they appear in the program. Executing end-of-file is equivalent
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6 to END 0, i.e. successful exit.
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7
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8 There are the following instructions ([X] means X is optional):
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9
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10 * LET [Variable] Expression
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11 Evaluates Expression and assigns the result to Variable (or \_ if
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12 Variable is omitted).
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13
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14 * WUNT [Value] Expression
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15 Writes the result of Expression to Value (which must yield an IO handle)
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16 if specified; otherwise it writes to \AUSG (standard output). Sets \_.
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17
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18 * IF Expression
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19 Jumps to the corresponding ELSE or FI instruction if Expression yields
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20 false. "Corresponding" means it skips intervening IF-FI groups. If no
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21 ELSE or FI can be found, jumps to the beginning of the program.
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22
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23 * ELSE
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24 Jumps to the corresponding FI instruction if present or to the beginning
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25 of the program otherwise.
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26
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27 * FI, END IF
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28 Serves as an end point for IF and ELSE jumps. Does nothing.
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29
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30 * GOTO Expression
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31 Jumps to the next line whose dynamic label is equal to the result of
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32 Expression. Search wraps around at end-of-file.
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33
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34 * GOFOR Expression
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35 Jumps to the previous line whose dynamic label is equal to the result of
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36 Expression. Search wraps around at beginning-of-file.
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37
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38 * CLAUDS Expression
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39 Closes the IO handle returned by Expression. Sets \_.
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40
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41 * SET [Value] Expression
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42 Writes the character represented by the number returned by Expression to
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43 the IO handle specified by Value (or \AUSG if Value is omitted). Sets
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44 \_.
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45
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46 * #!
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47 A comment. The rest of the line is ignored.
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48
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49 * REM
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50 A comment. The rest of the line is ignored. REM comments may be nested.
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51
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52 * # Expression
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53 Calls the C function system(3) with the result of Expression, i.e. runs
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54 the local command line interpreter. Sets \_.
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55
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56 * NEXT Label
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57 Jumps to Label, which must be a static label.
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58
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59 * ANRUF Expression
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60 Calls the next instruction with the dynamic label specified by
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61 Expression, i.e. it remembers the instruction it came from. Search wraps
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62 around at end-of-file. Sets \_ on returning.
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63
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64 * ABRUF Value Expression
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65 Calls the previous instruction with the dynamic label specified by
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66 Value, passing Expression as argument. Search wraps around at
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67 beginning-of-file. Sets \_ on returning.
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68
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69 * KTHX Expression
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70 Returns Expression from the current call. Equivalent to END if not in a
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71 call.
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72
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73 * LEET [Variable] Expression
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74 Similar to LET but the old value of Variable (if any) is restored at the
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75 following KTHX.
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76
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77 * END Expression
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78 Exits the program with a status of Expression. If Expression is -1,
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79 exits with EXIT_FAILURE.
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80
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81 * IACS Expression
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82 Throws Expression as an exception.
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83
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84 * FLUSH Expression
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85 Forces a write of all buffered data for the IO handle returned by
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86 expression, which must be opened for writing. Sets \_.
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87
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88 * RESET Expression
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89 Clears the end-of-file and error flags for the IO handle returned by
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90 Expression.
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91
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92 * Label Expression
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93 Calls the instruction with the static label Label, setting \@ to
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94 Expression. Sets \_ on returning.
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95
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96 * Expression
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97 Prints the result of Expression to \AUSG.
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