ctype
["Little Useful Bits" Library]

The ANSI-C standard <ctype.h> interface works fine for strings containing characters encoded with the ASCII 7-bit coding. However when you use characters outside this range things start to get ambiguous. More...

Functions
bool_t	lub_ctype_isdigit (char c)
bool_t	lub_ctype_isspace (char c)
char	lub_ctype_tolower (char c)
char	lub_ctype_toupper (char c)

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Detailed Description

The ANSI-C standard <ctype.h> interface works fine for strings containing characters encoded with the ASCII 7-bit coding. However when you use characters outside this range things start to get ambiguous.

The default manner in which to represent a string in C is to use a "char *". (NB. this is a signed type) The interfaces presented in <ctype.h> take signed integers. When a character greater than 128 is passed as a "char" to isspace() (e.g. the british pound sign "£") then a negative value is passed into the function/macro. A typical implementation (e.g. VxWorks) may use the passed argument as an offset into a lookup table, negative values in this case cause problems...

This utility provides an interface which avoids this ambiguity by passing "char" characters directly rather than converting to "int".

This component currently only contains those operations which are required by the current CLISH/LUB implementations. It can be extended on an as needed basis.

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Function Documentation

bool_t lub_ctype_isdigit

(

char

c

)

This operation identifies whether a character is a decimal digit or not.

Precondition:

• none

Returns:

BOOL_TRUE - if the character is a decimal digit BOOL_FALSE - if the character is not a decimal digit

Postcondition:

• none

Parameters:

c	The character to check

bool_t lub_ctype_isspace

(

char

c

)

This operation identifies whether a character is a standard white space character. (space, tab, carriage-return, vertical tab, form-feed)

Precondition:

• none

Returns:

BOOL_TRUE - if the character is white space BOOL_FALSE - if the character is not white space

Postcondition:

• none

Parameters:

c	The character to check

char lub_ctype_tolower

(

char

c

)

This operation converts an uppercase letter to the corresponding lowercase letter.

Precondition:

• none

Returns:

If the parameter is a character for which lub_ctype_isupper() is true and there is a corresponding character for which lub_ctype_islower() is true then the corresponding character is returned. Otherwise the parameter is returned unchanged.

Postcondition:

• none

Parameters:

c	The character to convert

char lub_ctype_toupper

(

char

c

)

This operation converts a lowercase letter to the corresponding uppercase letter.

Precondition:

• none

Returns:

If the parameter is a character for which lub_ctype_islower() is true and there is a corresponding character for which lub_ctype_isupper() is true then the corresponding character is returned. Otherwise the parameter is returned unchanged.

Postcondition:

• none

Parameters:

c	The character to convert

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