Text Interface

The Text interface provides procedures that work on strings. The `T' type in the procedure declarations below is really the built-in type `TEXT'.

PROCEDURE Equal(t, u: T): BOOLEAN;

Return "TRUE" if "t" and "u" have the same length and (case-sensitive) contents.

PROCEDURE Compare(t1, t2: T): [-1..1];

Compares strings "t1" and "t2" using lexicographic rules. Returns:

-1 if "t1" < "t2"
0 if "t1" = "t2"
+1 if "t1" > "t2"

PROCEDURE GetChar(t: T; i: CARDINAL): CHAR;

Return the i'th character of "t", i IN [0..LENGTH(t)-1]. It is a checked runtime error if i >= Length(t).

PROCEDURE Length(t: T): CARDINAL;

Return the number of characters in "t".

PROCEDURE Empty(t: T): BOOLEAN;

Equivalent to "Length(t) = 0".

PROCEDURE Sub(t: T; start: CARDINAL; length: CARDINAL := LAST(CARDINAL)): T;

Return a sub-sequence of "t": empty if "start >= Length(t)" or "length = 0"; otherwise the subsequence ranging from "start" to the minimum of "start+length-1" and "Length(t)-1".

PROCEDURE FindChar(t: T; c: CHAR; start := 0): INTEGER;

If "c = t[i]" for some "i" in "[start~..~Length(t)-1]", return the smallest such "i"; otherwise, return -1.

PROCEDURE SetChars(VAR a: ARRAY OF CHAR; t: T);

For each "i" from 0 to "MIN(LAST(a), Length(t)-1)", set "a[i]" to "GetChar(t, i)".

PROCEDURE FromChar(ch: CHAR): T;

Return a text containing the single character "ch".

PROCEDURE FromChars(READONLY a: ARRAY OF CHAR): T;

Return a text containing the characters of "a".

PROCEDURE Hash(t: T): Word.T;

Return a hash function of the contents of "t".

PROCEDURE FindCharR(t: T; c: CHAR; start := LAST(INTEGER)): INTEGER;

If "c = t[i]" for some "i" in "[0~..~MIN(start, Length(t)-1)]", return the largest such "i"; otherwise, return -1.