kalmar/Groups.jl
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add issubword, issubsymbol

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kalmarek 2020-03-25 03:38:33 +01:00
parent f7bf1598ee
commit 9bb2aba6f6
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1 changed files with 22 additions and 1 deletions
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src/Groups.jl
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@ -348,11 +348,32 @@ end
#
# Replacement of symbols / sub-words
#
###############################################################################
issubsymbol(s::GSymbol, t::GSymbol) =
s.id == t.id && (0 ≤ s.pow ≤ t.pow || 0 ≥ s.pow ≥ t.pow)
function issubsymbol(s::FreeSymbol, w::GWord, sindex::Integer)
@boundscheck 1 ≤ sindex ≤ syllablelength(w) || throw(BoundsError(w, sindex))
return issubsymbol(s, syllables(w)[sindex])
end
function issubword(z::GWord, w::GWord, sindex::Integer)
isempty(z) && return true
@boundscheck 1 ≤ sindex ≤ syllablelength(w) || throw(BoundsError(w, sindex))
n = syllablelength(z)
n == 1 && return issubsymbol(first(syllables(z)), syllables(w)[sindex])
lastindex = sindex + n - 1
lastindex > syllablelength(w) && return false
issubsymbol(first(z), syllables(w)[sindex]) || return false
issubsymbol(syllables(z)[end], syllables(w)[lastindex]) || return false
for (zidx, widx) in zip(2:n-1, sindex+1:lastindex-1)
syllables(z)[zidx] == syllables(w)[widx] || return false
end
return true
end
"""doc
Find the first linear index k>=i such that Z < W.symbols[k:k+length(Z)-1]
"""