hasChar: String Prefix and Suffix Checking

Description

These functions return a function for determining if a given prefix, suffix, or set of characters passed to this function exists in a character string passed to the returned function.

Usage

hasChar(toCheck, what = "")
hasPrefix(aPrefix)
hasSuffix(aSuffix)

Arguments

aPrefix

character string to be used as the prefix to be checked for

aSuffix

character string to be used as the suffix to be checked for

toCheck

toCheck a character string to be used to check to see if it exists in a character string passed to the returned function

what

what a character string defining whether toCheck will be used as a prefix (what = "prefix"), suffix (what = "suffix"), or a set of characters (what = "") to check the character string passed to the returned function

Value

A function which itself returns a logical (of length 1) indicating if the prefix/suffix is found (TRUE) or not.

Details

The prefix (or suffix) is passed to hasPrefix (or hasSuffix) and then the returned function can be used to check for the existence of that prefix (suffix) in a string passed to that function.

hasChar is a more general function that determines the existence of prefix, sufix, or a set of a characters in a character string passed to the returned function.

Examples

Run this code

# Function for checking for a prefix "xxx" :
chkPfun <- hasChar("xxx", what = "prefix")
# Function for checking for a suffix ".tex" :
chkSfun <- hasChar(".tex", what = "suffix")

chkPfun("xxx.tex")
chkPfun(".xxx")
chkSfun("xxx.tex")
chkSfun("yyyyy")
chkSfun("yxxx.text")