string_code(?Index, +String, ?Code)

Index

Variable or integer between 1 and the length of String

String

String

Code

Variable or non-negative integer

Description

The predicate may be used to extract the Index'th character, to find the position(s) of a particular character code, or to enumerate all positions and character codes in the string.

For simply extracting the Index'th character code from a string, the deterministic variant get_string_code/3 might be preferred for efficiency and stricter error checking.

For backward compatibility with earlier versions of ECLiPSe, the call pattern string_code(+String,+Index,-Code) is also allowed.

Modes and Determinism

• string_code(+, +, -) is det
• string_code(-, +, +) is nondet
• string_code(-, +, -) is nondet

Fail Conditions

Exceptions

(4) instantiation fault

String is uninstantated

(5) type error

String is instantiated, but not a string

(24) number expected

Index is instantiated, but not an integer

(5) type error

Code is instantiated, but not an integer

(6) out of range

Index or Code is a negative integer

Examples

   string_code(1, "abc", 0'a).        % succeeds
   string_code(1, "abc", 97).         % succeeds
   string_code(3, "abc", C).          % gives C = 0'c
   string_code(I, "abc", 0'c).        % gives I = 3
   string_code(I, "abcb", 0'b).       % gives I = 2 ; I = 4 on backtracking
   string_code(I, "ab", C).           % gives I=1,C=0'a ; I=2,C=0'b on backtracking

   string_code(2, "abc", 100).        % fails
   string_code(I, "abc", 0'd).        % fails
   string_code(0, "abc", C).          % fails
   string_code(4, "abc", C).          % fails
   string_code(I, "", C).             % fails

   string_code(1, S, 0'c).            % Error 4
   string_code(1, abc, C).            % Error 5
   string_code(1.5, "abc", C).        % Error 5
   string_code(I, "abc", b).          % Error 5
   string_code(-1, "abc", C).         % Error 6
   string_code(I, "abc", -1).         % Error 6

See Also