frontchar

[This is preliminary specification and subject to change.]

Group

Prolog predicates (more...)

Type

determ

Syntax

frontchar( STRING Inpstring, STRING START, STRING REST)

Flow patterns

(i,o,o),(i,i,o),(i,o,i),(i,i,i),(o,i,i)

Description:

Return the first character in a string
Remarks

The frontchar predicate operates as if it were defined by the equation:

String = (the concatenation of FirstChar and RestString)

The frontchar takes three arguments; the first is a string, the second is a char (the first character of the first string), and the third is the rest of the first string.
The frontchar can be used to split a string up into a series of characters, or to create a string from a series of characters, and to test the characters within a string. If the argument String is bound to a zero-length string, the predicate fails.

Sample:

No sample