Initial data commit

Task/Substring/Picat/substring.picat

@@ -0,0 +1,36 @@
+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)).