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‎docs/doc-plan.md‎

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MicroCode programs consist of 5 pages, numbered 1 - 5.
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Execution always starts on page 1. Before execution
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starts, all variables are initialized to 0 and
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the current value of all sensors is cached.
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# The MicroCode Language
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A page consists of a sequence of rules (R):
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## Syntax
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P := page-D R\*
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In the following, a word in ALLCAPS refers to a non-terminal in
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MicroCode's grammar. Words in lowercase are terminal symbols and
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may have dashes and other symbols in them. <float> is a floating
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point number; <pos> is an integer greater than zero. Comments follow //.
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Each rule has an option when section W and an optional do section D.
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A program (PROG) consists of 5 pages, number 1-5, each with a possibly empty sequence of
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rules RULE:
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R := when [W] do [D]
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PROG := page-1 RULE\* page-2 RULE\* page-3 RULE\* page-4 RULE\* page-5 RULE\*
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The when section specifies an event of interest
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and, optionally, a filter on that event.
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The do section specifies an action and, optionally,
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parameters to that action.
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Each rule has an option when section WHEN and an optional do section DO.
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RULE := when [WHEN] do [DO]
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The WHEN section specifies an event of interest and, optionally, a filter on that event.
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The DO section specifies an action and, optionally, parameters to that action.
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Some actions can be repeated.
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W :=
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| page-start [TS]
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| timer [TS]
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| press [PK]
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| release [PK]
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| move [MK]
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| sound [loud | quiet | C]
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| temperature [UD | C]
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| light [UD | C]
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| magnet [UD | C]
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| radio-receive [C]
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| variable-X-set [C]
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| variable-Y-set [C]
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| variable-Z-set [C]
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UD := up | down
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TS := (1/4-second | 1-second | 1-random-second | 5-seconds)\*
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PK := button-A | button-B | logo | pin-0 | pin-1 | pin-2
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MK := shake | tilt-left | tilt-right | ...
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C := CO V
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CO :=
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| equals
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| not-equals
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| less-then
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| less-then-or-equal
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| greater-than
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| greater-than-or-equal
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V :=
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| A
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| A + V
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| A / V
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| A - V
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| A \* V
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| random PV
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A :=
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| <float>
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| var-X | var-Y | var-Z
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| light-value | sound-value | temp-value | magnet-value
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| radio-value
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PV :=
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| int>0
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| int>0 + PV
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| int>0 \* PV
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D :=
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WHEN :=
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| page-start [TS] // fires (once) when control transitions to this page, with optional delay
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| timer [TS] // set a timer to fire after a delay, execute repeatedly after associated action completes
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| press [PK] // fire on press of specified button PK
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| release [PK] // fire on release of specified button PK
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| move [MK] // fire on specified accelerometer event MK
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| sound [loud | quiet | C] // fire on loud/quiet event or comparison C of current sound level (0-255)
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| temperature [UD | C] // fire on UD event or comparison C of current temperature (in Celcius)
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| light [UD | C] // fire on UD event or comparison C of current light level (0-255)
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| magnet [UD | C] // fire on UD event or comparison C of current magnetic level
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| radio-receive [C] // fire when number arrives via radio, subject to optional comparison C
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| variable-X-set [C] // fire after variable X has been assigned, subject to optional comparison C
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| variable-Y-set [C] // fire after variable Y has been assigned, subject to optional comparison C
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| variable-Z-set [C] // fire after variable Z has been assigned, subject to optional comparison C
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UD := up | down
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TS := (1/4-second | 1-second | 1-random-second | 5-seconds)\* // sum the sequence of times
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PK := button-A | button-B | logo | pin-0 | pin-1 | pin-2
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MK := shake | tilt-left | tilt-right | ...
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Sensors and variables may be compared to values using C; sensors may also have events
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C := CO E
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Comparison operators CO are as follows:
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CO :=
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| equals
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| not-equals
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| less-then
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| less-then-or-equal
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| greater-than
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| greater-than-or-equal
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An expression E is either atomic A, a binary expression, or a randomly chosen value:
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E :=
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| A
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| A + E
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| A / E
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| A - E
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| A * E
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| random PE
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An atomic value A is either a floating point number, one of the three variables,
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or the current value of one of the four sensors, or the last value received over radio:
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A :=
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| <float>
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| var-X | var-Y | var-Z
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| light-value | sound-value | temp-value | magnet-value
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| radio-value
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A positive (integer) expression PE is
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PE :=
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| <pos>
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| <pos> + PE
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| <pos> * PE
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DO :=
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| show-number [V]
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| show-image (image)_ [repeat [PV]]
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| play-sound (sound)_ [repeat [PV]]
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| play-music (notes)\* [repeat [PV]]
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| show-image (image)_ [repeat [PE]]
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| play-sound (sound)_ [repeat [PE]]
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| play-music (notes)\* [repeat [PE]]
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| radio-send [V]
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| radio-set-group [PV]
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| radio-set-group [PE]
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| set-variable-X [V]
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| set-variable-Y [V]
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| set-variable-Z [V]
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| switch-page [PG]
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PG := | page-1 | page-2 | page-3 | page-4 | page-5
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PG := | page-1 | page-2 | page-3 | page-4 | page-5
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## Semantics
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Before execution starts, all variables are initialized to 0 and
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the current value of all micro:bit/jacdac sensors is cached.
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Execution begins by transitioning to page 1.

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