RosettaCodeData/Task/Substring/Picat/substring.picat

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go =>
S = "Picat is fun",
N = 3,
M = 4,
C = 'i', % must be a char
SS = "is",
test(S,N,M,C,SS).
test(S,N,M,C,SS) =>
println($test(S,N,M,C,SS)),
% - starting from n characters in and of m length;
println(1=slice(S,N,N+M)),
println(1=S[N..N+M]),
% - starting from n characters in, up to the end of the string;
println(2=S.slice(N)),
% - whole string minus last character;
println(3=but_last(S)),
println(3=S[1..S.len-1]),
% - starting from a known character within the string and of m length;
println(4=substring4(S,C)),
% - starting from a known substring within the string and of m length.
println(5=substring5(S,SS,M)),
nl.
but_last(S) = slice(S,1,S.length-1).
substring4(S,C) = slice(S,S.find_first_of(C)).
% find is non-deterministic, hence the once/1
substring5(S,SS,M) = slice(S,Start,Start+M) =>
once(find(S,SS,Start,_End)).