# tones.fst
# D. Gibbon, 2008-08-11

# ===============================================================

# DESCRIPTION

# The automaton models the following rules for a two-tone terracing language:
# H -> h-constant / # _
# L -> l-constant / # _
# H -> h-upsweep / h _
# L -> l-upstep / h _
# H -> h-downstep / l _
# L -> l-downdrift / l _

# That is:
# 1. the intial H or L tone is an approximate h or l constant, respectively.
# 2. Following a H tone:
# 	- a H tends to be realised higher (upsweep),
# 	- a following L tends to be raised (upstep, e.g. to mid).
# 3. Following a L tone:
# 	- a L tends to be realised lower (downdrift),
# 	- a following H tends to be lowerd (downstep).
# 4. Only two well-defined levels of representation are required:
# 	- underlying (represented by upper case),
# 	- surface phonetic (represented by lower case).
# 5. There is no extrinsic rule ordering: all rules apply opportunistically.
# 6. The rules
# 	- only depend on the immediately preceding tone,
# 	- are *not* context-sensitive in the technical sense.

# Typical input/output behaviour:

# ndfstinterpreter.py off tones.fst forward on 'H H L L H H L L'
# => H:h-cons H:h-upsw L:l-upst L:l-dwnd H:h-dwns H:h-upsw L:l-upst L:l-dwn

# ndfstinterpreter.py off tones.fst forward off 'H H L L H H L L'
# => h-cons h-upsw l-upst l-dwnd h-dwns h-upsw l-upst l-dwnd

# ndfstinterpreter.py off tones.fst reverse off 'h-cons h-upsw l-upst l-dwnd h-dwns h-upsw l-upst l-dwnd'
# => H H L L H H L L

# ndfstinterpreter.py off tones.fst reverse on 'h-cons h-upsw l-upst l-dwnd h-dwns h-upsw l-upst l-dwnd'
# h-cons:H h-upsw:H l-upst:L l-dwnd:L h-dwns:H h-upsw:H l-upst:L l-dwnd:L

# Equivalent finite state netowrk:
# Rough ASCII art representation
# Arrowheads are indicated by {>, <, ^, V}
# Phonetic output is abbreviated
#
#                  /\ H:upsw
#                 V /
#         -----> (q1)
#    H:c/         ^|
#      /          ||
# (q0)     H:dwnst||L:upst
#      \          ||
#     Lc\         |v
#         -----> (q2)
#                 / ^
#         L:dwndr \/

# Equivalent regular expression:

# The central disjunction '|' covers H and L initial tones. 
# The other disjunctions permit demiterrace iterations and
# main terrace iteration.
# The final parenthesis permits correct termination.
# The Kleene operators signify zero or more ('*') or one ('?') occurrences.

# H:c ( H:upsw | L:upstp L:dwndr* H:dwnst )* ( L:upst L:dwndr* )? |
# L:c ( L:dwnd | H:dwnst H:upswp* L:upstp )* ( H:downst H:upswp* )?

# ===============================================================

initial=q0
terminal=q1,q2

fst=
	q0,H,h-cons,q1;
	q0,L,l-cons,q2;
	q1,H,h-upsw,q1;
	q1,L,l-upst,q2;
	q2,H,h-dwns,q1;
	q2,L,l-dwnd,q2